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I am considering building a small home server. I'd like to encrypt some folders on this server, therefore using the instruction set aes-ni which is supported by newer (mostly Intel) chips would be advantageous.
Is there a way to use aes-ni with Debian, or is there at least an alternative kernel that supports it?
[edit... |
It does look like it is configured in the config you listed (as CONFIG_CRYPTO_AES_NI_INTEL=m, which means configured as a module), but regardless, it is easy to build your own custom Debian kernels. See the Debian Kernel Handbook. You want 1.10, the version online is 1.09 which is out of date. The only downside of com... | Use aes-ni in Debian |
1,594,598,856,000 |
When you want to limit CPU time per process, you can do it via cgroups. There are two parameters that can do the job: cpu.cfs_period_us and cpu.cfs_quota_us.
There's some info on the parameters here:
cpu.cfs_period_us: The duration in microseconds of each scheduler period, for bandwidth decisions. This defaults to ... |
As the quote says lower number give lower latency. A process does not have to wait long before it is scheduled: Every process gets a turn, soon. However there is more re-scheduling overhead: Every time the time runs out, and there are other processes ready to run, there is a re-schedule.
Re-scheduling involves saving... | What are the benefits of using longer/shorter periods in cpu.cfs_period_us? |
1,594,598,856,000 |
When I run command like iostat -dkx 2 2 via ssh, I get the expected result, but the processes on the local computer are saying alive in status "interruptible sleep". Why is this happening? Is there a way to find out the reason of that behavior?
full command:
$ ssh -o ConnectTimeout=4 -o ChallengeResponseAuthentication... |
There seems to be nothing wrong. The process you are looking at (ssh) has simply nothing to do at the moment you are taking it's process stat.
As long as there is no output from the remotely started command, the "select" blocks, and the process is sent to sleep.
| How to find out the reason why ssh processes are hanging? |
1,594,598,856,000 |
I'm not sure at which level I am having a problem.
System is a LeopardBoard DM368 running TI's own SDK / LSP / BusyBox kernel, the core Linux kernel is 2.6.x so using serial_core.c driver model.
By default the system has one UART enabled, UART0, mounted as /dev/ttyS0 which is also used/invoked via the bootargs console... |
mknod /dev/ttyS1 c 4 65
(if /dev is read-only use any writable directory mounted without the option nodev)
If the node is created without errors you can check if your patch is working reading/writing to the node or with any terminal emulator.
The problem is that the node isn't created?
If you're using some auto-magic ... | ttyS1/uart1 initialised but not accessible through /dev/ttyS1 |
1,594,598,856,000 |
I'm using Buildroot to create a Linux system for the NXP LPC3250 microcontroller.
There are patches to the vanilla kernel to make it compatible with the LPC3250 controller:
http://git.lpclinux.com/
I would like to build Kernel 2.6.39.2, but my Buildroot system always makes a 2.6.34 kernel!
I have set the GIT reposito... |
Not really an answer, but it doesn't fit a comment due to formatting:
What happens when you do the following:
cd /home/user/projects/buildroot
make clean
make distclean
Copy target system's /proc/config.gz to host /tmp
Then take the existing kernel config and translates it to the new kernel version by answering the v... | Buildroot ignoring configuration files - building wrong kernel |
1,594,598,856,000 |
this seems like a very basic question, but after searching the web for 2 hours I couldn't find any real help on the subject and it's driving me nuts.
It's brutally simple: I have a radeon 4670 video card (rv770xt), use Arch Linux' repo kernel and have monitors on VGA and DVI. KMS is enabled and doing fine.
The VGA mon... |
You could use a udev rule and fbset to force the framebuffer resolution on both displays, which may go some way to achieving what you are after.
The udev rule would be along the lines of /etc/udev/rules.d/81-framebuffer-hack.rules:
KERNEL=="card0-DVI", SUBSYSTEM=="drm", ATTR{dpms}=="On", ATTR{enabled}=="enabled", ATTR... | VGA and DVI, set default kernel console to one |
1,594,598,856,000 |
Sometimes after I boot up the machine, I get no sound in flash videos. First I didn't know why it was happening, but as I read a few articles here and there, I found out it was because of my USB webcam (logitech) - ALSA was messing something up and didn't know how to handle sound drivers well (so they say). So one of ... |
You might be able to fix it by creating a ~/.asoundrc see http://alsa.opensrc.org/.asoundrc
Specifically you want the opposite of the case here: http://alsa.opensrc.org/.asoundrc#Default_PCM_device
so aplay -L with out the usb audio in and and asoundrc like this might work:
pcm.!default front:Intel
If your card (Like... | Sometimes no sound in flash videos after boot? |
1,594,598,856,000 |
I have two x86_64 kernels compiled on the same machine against the same code (4.15.0 in Linus' source tree).
The config files were produced by running make localmodconfig against that source, using different, larger original config files coming from different distros: Arch and Slackware respectively. I'll nickname the... |
I believe the picture is as in my last edit above; I just did not know enough about the process of reserving memory to realize when I asked the question: it all boiled down to the larger kernel having more of the drivers built in rather than modularized.
Incidentally, I did want to put this to some (remotely) practic... | different kernels report different amounts of total memory on the same machine |
1,424,774,855,000 |
It's clear that you need the kexec syscalls in the 'first' kernel. But does the kernel that should get loaded (with kexec_load and reboot) need to be compiled with kexec?
If yes, what extra code needs to get executed inside the kernel to do a kexec boot instead of a normal boot?
|
I haven't seen an explicit statement about that and I haven't given it a try but I guess this is not necessary. In addition to my guess the man pages says:
kexec performs the function of the boot loader from within the kernel.
An adaption of the kernel to be loaded would be necessary only if some black magic instead... | does the second kernel need kexec enabled |
1,424,774,855,000 |
Is there any actual difference between
iptables -P FORWARD DROP
and
net.ipv4.ip_forward = 0
?
I know that one is a firewall command while the other one is a kernel option. But:
I don't know whether net.ipv4.ip_forward = 0 is enforced by netfilter or by the kernel directly.
I don't know if there is any overhead asso... |
When you disable packet forwarding between interfaces the FORWARD chain is ignored at all. So, in connection to performance which is where your question is targeted it does not make any difference.
You can check it doing:
iptables -L -vnx
HTH
| Is there any difference between these two configuration options? |
1,424,774,855,000 |
I think my Linux laptop has been hacked, for three reasons:
Whenever I saved files into the Home folder, the files wouldn't appear - not even in the other folders on my computer.
An unfamiliar .txt file has showed up in my Home folder. Having noticed it, I didn't open it. I immediately had a suspicion that maybe my l... |
Based on the details in your question, your system is clean.
You're making backups. OK.
clamav comes up clean. That's fine, too.
Based on your output of chkrootkit, your system is clean. Those files listed as suspicious are benign. The Ebury/Windigo detection is a false positive: https://github.com/Magentron/chkrootk... | bash: /var/log/rkhunter.log: Permission denied (as root - Linux Mint 18.3) |
1,424,774,855,000 |
Who are the authors of the pure Linux kernel from scratch, which was integrated with GNU tools and formed the full GNU/Linux Operating system in the 1990s? I have read some wiki articles but I haven't got any clear cut idea on the history.
|
The wikipedia page has a fairly clear history. Linus Torvalds, then a student, wrote his own kernel in the summer of 1991 because he was unhappy with the available Unix kernels: Unix itself (with the Bell Labs code) was extremely expensive (even PC unices such as Xenix), there was Andrew Tanenbaum's MINIX but it was o... | Who wrote the "Linux kernel" (Linus Torvalds and his team)? |
1,424,774,855,000 |
Given the limited fixed size of kernel stack, my guess is that although theoretically we might have a recursive function if its recursion doesn't go too deep, pragmatism would suggest to do away with recursive functions all together, to be on a safer side. After all, too much of recursion can result in wiping off the ... |
Yes!
Maybe some of the recurive calls are either documented or part of function names? Then, a find/grep should reveal them. Here is a command to do it:
find /usr/src/linux/ -name "*.c" -exec grep recursive {} ";" -ls
Piping this through | wc -l gives me 270, which is, since -ls prints one additional line per file, ... | Does the linux kernel (specifically 2.6 onwards) have any recursive function? |
1,424,774,855,000 |
Just out of curiosity, I am interested in compiling the Linux kernel with both the clang and zapcc compilers; one at a time.
I can't find a guide to follow. Only GCC is getting used to compile the Linux kernel.
How do I compile the Linux kernel with other compilers?
|
The kernel build allows you to specify the tools you want to use; for example, to specify the C compiler, set the CC and HOSTCC variables:
make CC=clang HOSTCC=clang
The build is only expected to succeed with GCC, but there are people interested in using Clang instead, and it is known to work in some circumstances (s... | How do I compile the Linux kernel with Clang? [closed] |
1,424,774,855,000 |
I'm asking about functions like printf that a lot of processes might use and also need the help of kernel for stuff like system calls.
What is the step-by-step description in detail for what happens? Because I'm a little confused in this area, I have these questions:
Are the instructions for the printf function insi... |
printf is implemented by the C library, it’s not part of the kernel. (The kernel does have its own equivalent, more or less, but that’s not available to user processes.) So a user process calling printf doesn’t call into the kernel immediately. If printf’s output gets written¹, that happens by calling write, which is... | What exactly happens in virtual memory when I call a function like printf in Linux? [closed] |
1,424,774,855,000 |
I'm trying various ways of Linux installation (from iso, flash, iso on flash, kernel on flash, root FS in iso-file on flash...) and want to understand what's going on.
My question is: is it possible, given the built kernel and ramfs files from a distribution (vmlinuz and initrd), to find out, where they are going to l... |
It is given at boot time by your bootloader, for example Grub.
To see with which arguments your kernel was started, do this:
$ cat /proc/cmdline
For me, this ouputs:
BOOT_IMAGE=/vmlinuz-3.5.0-13-generic root=/dev/mapper/crypt-precise--root ro
So the initrd/initramfs will try to mount my /dev/mapper/crypt-precise--ro... | Given vmlinuz and initrd.gz, how do I find out, where the kernel is going to load / (root) file system from? |
1,424,774,855,000 |
I saw in my syslog kernel.perf_event_max_sample_rate get changed.
I was wondering if I could write a quick script to log this variable every few minutes. Currently it is:
sysctl -a | grep kernel.perf_event_max_sample_rate
In the man page sysctl says
sysctl - configure kernel parameters at runtime
Does that mean tha... |
So one of the big things about learning to Unix is reading the bloody man page:
I'm not just being a get off my lawn grumpy old man, there REALLY IS valuable information in there. In this case:
DESCRIPTION
sysctl is used to modify kernel parameters at runtime. The parameters available are those listed under /proc/sy... | View current kernel parameters? |
1,424,774,855,000 |
I'm learning now how to compile and boot linux kernels. Is there a way to boot kernels in a virtual machine, rather than messing my system? I use VMWare Workstation on Windows 8. Can I use that to boot my linux kernel?
|
I'm learning now how to compile and boot linux kernels. Is there a way to boot kernels in a virtual machine, rather than messing my system? I use VMWare Workstation on Windows 8.
I am assuming, based on your wording, that you don't have a UNIX-like working environment. To build your own kernel, you have to have one... | Boot my kernel in a Virtual Machine? |
1,424,774,855,000 |
I've always wondered how the kernel passes control to third-party code, or specifically distribution-specific code, during boot.
I've dug around in GRUB's configuration files, suspecting a special parameter to be passed to the kernel to let it know what to do once it has booted successfully, but unable to find anythin... |
It's hardcoded, but you can override the defaults by the kernel parameter init=....
From init/main.c:
if (execute_command) {
run_init_process(execute_command);
printk(KERN_WARNING "Failed to execute %s. Attempting "
"defaults...\n", execute_command);
}
run_init_process("/sbin/init");
run_init_process("/et... | How does the kernel "give up" control to distribution-specific initialization? |
1,424,774,855,000 |
If I want to build a custom kernel for an ARM architecture, do I need to :
a) Download the kernel from kernel.org, make changes to the kernel, build it using some cross compiler (like code sourcery or something)
b) Find an ARM specific kernel from somewhere, find some patches, compile it using some ARM specific tool... |
The Linux kernel source tarball and git repository includes the code for all supported architectures, such as ARM.
The subdirectory Documentation/arm/ contains some ARM related documents which you should probably have a look at before going further.
The ARM specific code is located in the arch/arm/ subdirectory (some ... | Is there a different linux kernel for different architectures? |
1,424,774,855,000 |
I have extremely low space in /boot and wondering I could get rid if a few things. This is the output of sudo ls -al /boot:
total 216002
drwxr-xr-x 4 root root 3072 Feb 20 12:33 .
drwxr-xr-x 23 root root 4096 Feb 20 12:30 ..
-rw-r--r-- 1 root root 1271689 Oct 22 2015 abi-3.19.0-32-generic
-rw-r--... |
If you are running 4.4.0-63, you can delete all the vlinuz-*, System.map-*, initrd.img-*, config-*, abi-*, except those containing the string 4.4.0-63. However, for resilience , I would keep the previous version around i.e. those files containing 4.4.0-62.
You may have to update GRUB or whatever bootloader you u... | wondering if I can delete what I think are old kernel images |
1,424,774,855,000 |
I read that there are two modes called “kernel mode” and “user mode” to handle execution of processes. (Understanding the Linux Kernel, 3rd Edition.) Is that a hardware switch (kernel/user) that is controlled by Linux, or software feature provided by the Linux kernel?
|
Kernel mode and user mode are a hardware feature, specifically a feature of the processor. Processors designed for mid-to-high-end systems (PC, feature phone, smartphone, all but the simplest network appliances, …) include this feature. Kernel mode can go by different names: supervisor mode, privileged mode, etc. On x... | Are “kernel mode” and “user mode” hardware features or software features? |
1,424,774,855,000 |
Many of my modules are missing /sys/module/*/parameters directory and I can't check the module loaded parameters.
# printf "%s\n" /sys/module/*/parameters | wc -l
125
# lsmod | wc -l
151
# comm -13 <(printf "%s\n" /sys/module/*/parameters | xargs dirname | xargs basename -a | sort) <(lsmod | awk '{print $1}' | sort) |... |
In order for modules to have their parameters visible in /sys/module/*/parameters, the module needs to provide a module_param_cb() callback function for each parameter. Those functions will have to "know where to look" for the current setting of the respective parameter, so the sysfs filesystem driver can use them to ... | modules are missing /sys/module/*/parameters directories, how to enable them? |
1,424,774,855,000 |
when we run the sysctl -p on our rhel 7.2 server1 we get
sysctl -p
fs.file-max = 500000
vm.swappiness = 10
vm.vfs_cache_pressure = 50
sysctl: cannot stat /proc/sys/pcie_aspm: No such file or directory
net.core.somaxconn = 1024
# ls /proc/sys/pcie_aspm
ls: cannot access /proc/sys/pcie_aspm: No such file or directory
... |
As revealed in the comments, there’s a
pcie_aspm=off
line in one of the files which sysctl -p reads. This causes sysctl to attempt to write to /proc/sys/pcie_aspm; if that doesn’t exist (and it won’t, it’s not a valid sysctl entry, it’s a kernel boot parameter), you’ll get the error shown in your question.
| sysctl -p failed on /proc/sys/pcie_aspm |
1,424,774,855,000 |
I am trying to compile the 5.4 kernel with the latest stable PREEMPT_RT patch (5.4.28-rt19) but for some reason can't select the Fully Preemptible Kernel (RT) option inside make nconfig/menconfig.
I've compiled the 4.19 rt patch before, and it was as simple as copying the current config (/boot/config-4.18-xxx) to the... |
Please enable EXPERT mode after launching make nconfig/menuconfig. Then you'll be able to select Fully Preemptible Kernel (RT) option.
| Trouble selecting "Fully Preemptible Kernel (Real-Time)" when configuring/compiling from source |
1,424,774,855,000 |
We are currently working on building a system for data visualisation for different sensors.
To make development of the Linux application possible we would need to emulate the behaviour of the different character devices as the device drivers and the hardware design aren't done yet.
So is there a way to receive the s... |
You could use cuse Character Device in Userspace which is a part of the fuse library, available as a package in most systems. An example "driver" is cuse.c.
When you compile and run this example as:
sudo ./cuse -f --name=mydevice
it creates /dev/mydevice and receives all the open, close, read, write, ioctl calls on ... | Emulating a character device from userspace |
1,424,774,855,000 |
Can you help me understand, why my SATA hotplug doesn't work? When I plug sata disk, lsblk doesn't change. There is only my system disk /dev/sda.
I have linux:
$ uname -a
Linux Z170-D3H 4.9.0-3-amd64 #1 SMP Debian 4.9.25-1 (2017-05-02) x86_64 GNU/Linux
Kernel settings:
$ cat /boot/config-4.9.0-3-amd64 | grep HOTPLUG... |
Problem was in wrong BIOS configuration.
Solution (for my motherboard Z170-D3H) is go to BIOS > Peripherals > SATA Configuration and here enable Hot Plug option for each SATA port. Then save settings and restart computer.
Now everything works properly!
| Sata hotplug doesn't work |
1,424,774,855,000 |
Which file in /proc gets read by the kernel during the boot up process? This was a question on my LPIC 101 test that I think I might have answered wrong. I searched on google and some other places but wasn't able to find an answer. Hoping one of you could provide. Thanks!
|
My question is, which file in /proc gets read by the kernel during the boot up process? This was a question on my LPIC 101 test...
Sounds like a trick question. The files in /proc aren't real files on disk (this is why they have a size of 0) and the nodes don't exist until the kernel mounts a procfs file system the... | Which file in /proc gets read by the kernel during the boot up process? |
1,424,774,855,000 |
I'm curious:
What, exactly are the benefits to statically linking modules into the kernel rather than loading through rc.conf, etc?
For example:
To add Linux emulation, I could add linux_enable="YES" to /etc/rc.conf, or I could link it into the kernel by adding options COMPAT_LINUX to my kernel config.
Is there actual... |
Statically linking used to be the only way to load a module which is think is the primary reason to having options like COMPAT_LINUX. Also, prior to loader, it used to be the only way to load modules necessary to get FreeBSD to get the necessary drivers to mount the root file system and boot FreeBSD. Nowadays, I don... | Difference between rc.conf, loader.conf and static kernel linking in FreeBSD |
1,424,774,855,000 |
Why are copy_from_user() and copy_to_user() needed, when the kernel is mapped into the same virtual address space as the process itself?
Having developed a few (toy) kernel modules for learning purposes, I quickly reliazed that copy_from_user() and copy_to_user() were needed to copy data from/to user-space buffers; ot... |
The address space mapping is the same on some (not all!) architectures, but even on architectures where they are the same, the protection levels aren’t. copy_from_user etc. serve three main purposes:
they check that the permissions on the memory to be read from or written to would allow the process running in user sp... | Why are `copy_from_user()` and `copy_to_user()` needed, when the kernel is mapped into the same virtual address space as the process itself? |
1,424,774,855,000 |
When configuring the Linux kernel, what are the advantages and disadvantages of enabling UTS namespaces? Would the new system be harmed if UTS namespaces were disabled?
|
UTS Namespaces are per-process namespaces allowing a process to have different namespaces for different resources. For example, a process could have a set of namespaces for the following:
mountpoints
PID numbers
network stack state
IPC - inter process communications
NOTE: the use of namespaces was limited only to ro... | Enabling UTS Namespaces in the Linux Kernel |
1,424,774,855,000 |
While reading about the Linux kernel I came across the notion of kernel data structures. I tried to find more information via Google, but couldn't find anything.
What are kernel data structures?
What are their requirements, usage, and access?
What's the organization of data structure inside the kernel?
Examples of ... |
The kernel is written in C. "Kernel data structures" would just refer to various formations (trees, lists, arrays, etc.) of mostly compound types (structs and unions) defined in the source, which C code is normally filled with stuff like that. If you don't understand C, they will not be meaningful to you.
Data struct... | What are "kernel data structures"? |
1,424,774,855,000 |
A few questions about FreeBSD
Where/how should I obtain the source code (ex. through terminal, Download off website)
How (on ubuntu) should I build it?
Before I build it can I customize it (in other words is possible)?
|
You can check the source for FreeBSD out of version control here. The developer's handbook answers a lot of questions about developing FreeBSD. Why aren't you building it from FreeBSD itself? It seems kind of... odd to be building from Ubuntu.
| FreeBSD source and how to build |
1,587,375,393,000 |
I can see my initrd is occupied almost 90 MB of disk but after extracting it via cpio , it contains only a 30 KB microcode :
$ cpio -it < initrd.img-5.4.0-18-generic
.
kernel
kernel/x86
kernel/x86/microcode
kernel/x86/microcode/AuthenticAMD.bin
62 blocks
I know that there should be a lot of files and tools which are... |
initramfs images contain multiple cpio archives; the name of your file suggests you’re using a Ubuntu derivative, so the simplest option for you to list the full contents is to use lsinitramfs:
lsinitramfs initrd.img-5.4.0-18-generic
To extract the contents, use unmkinitramfs:
unmkinitramfs initrd.img-5.4.0-18-generi... | Problem extracting the "initrd" archive in kernel 5.4 |
1,587,375,393,000 |
Background:
I recently read about a freedesktop.org-bug which allowed executing any systemctl command for uid > INT_MAX. Thus I ran:
root@host$> useradd -u 4000000000 largeuiduser
root@host$> su largeuiduser
largeuiduser@host$> systemctl ["whatever"]
[bug exists, and "whatever" gets executed]
largeuiduser@host$> e... |
In the Linux and BSD worlds, the kernel operates almost wholly in terms of numeric user and group IDs. There is a standardized C library that provides access to a user database, where names can be looked up from IDs and vice versa, which is how applications softwares get from names supplied by humans to the IDs need... | How essential are usernames ( compared to uids )? |
1,587,375,393,000 |
I know there is a syscall convention but what do you call the calling convention that precedes it that you see when you call to int 80 rather than syscall, like this.
mov rax,4 ; system call number (sys_write)
mov rbx,1 ; file descriptor (stdout)
mov rcx,hello ; message to write
mov rdx,12 ; message len... |
You question covers a number of topics, I’ll try to address them all.
I’m not sure there’s a single, canonical term for the way in which system calls are invoked, even less so for a specific way in which system calls are invoked (interrupt 0x80 as opposed to SYSENTER or SYSCALL). On x86-64, the documented system call... | What do you call the calling convention behind `int 0x80`? |
1,587,375,393,000 |
I am using a CentOS and I have enabled the USB driver for GSM and CDMA modems using make menuconfig.
But, how does it work? After changing in menuconfig, is the modification performed in the moment? Or do I have to compile the whole kernel in order to get this configuration?
|
With make menuconfig you only change the configuration file .config which is used in the compilation process. One doesn't need to use this menuconfig tool - there are other scripts for that or one can even edit .config by hand (although this is error prone and thus not recommended).
So in order to finish the task you'... | When are menuconfig changes performed? |
1,587,375,393,000 |
I've got OSX 10.9.5 . I want to build NetBSD (or at least it's kernel) on my OSX box. I've tried building the 'config' program but I can't find 'build.sh'. Is this possible and what would be the steps to do it? Thanks.
|
NetBSD has documentation here: Part V. Building the system
You might be able to compile a NetBSD kernel on OSX. At a minimum, you would need
the kernel source tree, i.e., /sys (which at least does not conflict with OSX's system directories).
whatever tools are needed, you probably have to download source and compile... | Can a bootable NetBSD be built on OSX? |
1,587,375,393,000 |
I recently installed my hard drive in a new computer and after some fiddling around I noticed my iptables rules were dropping DNS responses for some reason, turns out they were configured to allow stuff on eth0, but eth8 is used in this computer and everything was being dropped (not just DNS queires). Anyhow, I was us... |
Wireshark uses libpcap to fetch data from the NIC before it is handled by the OS. See the libpcap tutorial for an introduction to libpcap.
| How can Wireshark see packets dropped by iptables? |
1,587,375,393,000 |
I'm trying to add a system call using linux kernel 4.1.6 but all the documentation I can find is for older versions. Does anyone know how it's done in the newer kernels or have any good references?
There's supposed to be 3 steps:
Add to the system call table. I've worked out that they now use arch/x86/syscalls/syscal... |
According to _syscall(2) man page the _syscall0 macro may be obsolete and requires #include <linux/unistd.h>; indeed Linux 4.x don't have it
However, you might install musl-libc and use its _syscall function.
And you could simply use the indirect syscall(2) in your user code. So your testing program would be
#define... | How to add a system call in linux kernel 4.x |
1,587,375,393,000 |
I have a new system with debian (omv) a SSD hard drive for the OS and a software RAID 6 for the data.
I only saw now that I have very regular exceptions in my syslog. I'm worried now, what could cause those exceptions. Is it a software problem or is actually some hardware faulty? Can you actually read anything from th... |
The steps I took to fix it:
updated BIOS
In the BIOS, diabled the SATA IDE Combined Mode with this help
reading the kernel documentation about kernel parameters, since every solution online was about adding parameters to that.
I found out that my SSD actually only supports SATA speed 3.0Gbps with a good shell script... | What causes the ata exceptions in my syslog and how to solve them |
1,587,375,393,000 |
I was compiling a custom linux kernel for a newly installed machine, and after booting into the new kernel (3.12), the init process fails to find a root device, which I traced to the system getting an unknown partition table error on the device in question (/dev/sda). The generic kernel boots up and mounts the root pa... |
There are a bunch of options mostly named CONFIG_.*_PARTITION, you probably didn't set the one you need. These may only show up if you answer yes to CONFIG_PARTITION_ADVANCED (Advanced partition selection).
You're going to want (on a PC) at least:
CONFIG_MSDOS_PARTITION=y # traditional MS-DOS partition table
CON... | "unknown partition table" - misconfigured kernel |
1,587,375,393,000 |
I'm trying to build kexec as a module, but I'm running into a weird problem. My obj-m is:
obj-m += kexec.o machine_kexec.o relocate_kernel.o
When I run the makefile, it complains that there's "no rule to make target relocate_kernel.c, needed by relocate_kernel.o"
How should I be telling it to include the assembly f... |
As always, RTFM. Answering this and leaving it up to help others that may come across this. Per the Linux documentation project, I was using obj-m wrong:
Sometimes it makes sense to divide a kernel module between several source files.
Here's an example of such a kernel module.
[ Source files ... ]
And finally, th... | Assembly files in obj-m list when building kernel modules |
1,587,375,393,000 |
Some articles say that modules/drivers belong to kernel space as it take part in forming the kernel; (reference: http://www.freesoftwaremagazine.com/articles/drivers_linux)
While others say that only Ring0(directly interact with hardware)can be called kernel space(excluded modules/drivers as they are at Ring2). (ref... |
On AMD64 and clones, and ix86, Linux uses only ring 0 and 3. No other common architecture has the "rings" anyway, so using them fully would be totally non-portable. Besides, Linux is monolithic. The whole ring idea is to be able to run the microkernel on ring 0, and have service processes run on higher rings so they c... | Does linux modules/drivers belong to kernal space or user space |
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I've built a kernel with loadable module support for various reasons, one of them the possibility to compile modules and load them without rebooting. This is supposed to be useful when I need a module that I had not enabled in the kernel config.
Now, with drivers like nouveau, it's as easy as going to the source direc... |
Just go to your kernel source directory, make the changes you want, and make, then make modules_install.
That's all it takes.
If you want to build only one specific module, use:
make M=path/to/module/directory
For instance (from the kernel toplevel directory):
make M=fs/ext4
make M=fs/ext4 modules_install
To activat... | How do I build the iptables kernel module for a loaded kernel? |
1,587,375,393,000 |
I've read that I can boot the kernel without initrd, and I've also read that additional modules are loaded during the initrd stage -- as I understand it, for necessary drivers that weren't included in the kernel.
If I build the kernel with make defconfig && make, on what kind of hardware can I expect the kernel to boo... |
You can boot without initrd on any hardware. I never use it myself on desktops/laptops and home servers, because it just adds to boot time. The only situation where I've found it really necessary so far, is when your root filesystem is on an LVM (but I may be in error - there might be some way to go about this also).
... | When would an initrd be necessary? |
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I tried compiling a kernel from sources that I got from kernel.org (mainline) with make allyesconfig and make allmodconfig, but both builds resulted in a kernel, that won't boot.
I was thinking, that by compiling everything, It should work on close to any hardware. What am I doing wrong?
And how do I compile a working... |
One thing you can do is boot a working kernel, run lsmod, and make sure that all the modules listed are turned on in your config (either built-in or as modules).
It's easiest to start with a working config, and then tweak it. If you're lucky, your distribution ships the config file along with the kernel. For example... | How to compile a decent kernel from kernel.org? |
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So I found a bug, fixed it, and want to send the patch for it.
I followed the Write and submit your first Linux kernel patch youtube video, set up git-email, formatted everything, etc., and want to send it.
My issue: I don't want to send it alone but with an accompanying message and sample userspace code that gets fix... |
When you extract your commit, add --cover-letter to the git format-patch options. This will extract your commit with a 0001 prefix, and create a cover letter template with a 0000 prefix. You can edit that to contain your accompanying message and sample code, then send both with a single git send-email invocation: your... | How do I send a patch with an accompanying message to the Linux kernel? |
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I am trying kernel patching for the first time. I am not sure the following is encountered with an error and if I am doing it correctly. But in all tutorials and videos shows, .patch extension files, but I have a .xz file.
Downloaded stable release 5.12.1 from https://www.kernel.org:
root@learn:/usr/local/src# wget ht... |
This error message
Reversed (or previously applied) patch detected! Assume -R? [n]
... means that the patch command detected that your patch has already been applied to the sources. It suggests you to use patch -R but it's not what you want, since it would unapply the patch and thus you would get an earlier version ... | Kernel patching prompts “Reversed (or previously applied) patch detected! Assume -R? [n]” |
1,587,375,393,000 |
Updated my packages today on my Lenovo Thinkpad X1 Carbon (6th Gen). I didn't expect anything to happen but it did. The Mute indicator LED's on the F1 and F4 key stopped working.
I actually know this will be fixed soon. I'm just making a question so that I can answer it, in case anyone else is looking for a solution.
|
Situation
A Lenovo Thinkpad X1 Carbon running Arch Linux updated its packages on December 15th since October 22nd. After a reboot the LED indicators of the Mute Mic and Mute Speakers keys stopped working.
Investigation
I started my investigation by simply searching for phrases like "Mute LED not working" but couldn't ... | Lenovo Thinkpad Mute LED Stopped working after update |
1,587,375,393,000 |
This is a follow up question from my previous question.
Based on the answer, a system call is an example of when we jump into kernel part of virtual memory of our process.
What are other examples of a normal process (non kernel) using this part of virtual memory other than system calls? like is there any function ca... |
Processes running in user mode don’t have access to the kernel’s address space, at all. There are a number of ways for the processor to switch to kernel mode and run kernel code, but they are all set up by the kernel and happen in well-defined contexts: to run a system call, to respond to an interrupt, or to handle a... | When do we jump into kernel part of our process virtual memory other than when we use system calls? (In Linux) |
1,587,375,393,000 |
I want to add a public key from the keypair that I used to sign my kernel module, into system_keyring. However, there's a problem:
With the command of cat /proc/keys | grep system_keyring, I've got the entry (ID) of system_keyring. However, when trying to add my public key with this command: keyctl padd asymmetric "" ... |
The system keyring gets its contents from five sources:
keys embedded in kernel at compile time (obviously not changeable without recompiling)
UEFI Secure Boot variable db - depending on your firmware, you might or might not be able to change this
UEFI Secure Boot variable dbx- as the previous one, but this is a blac... | How to add a public key into system keyring for kernel without recompile? |
1,587,375,393,000 |
I found zstd in /drivers/block/zram/zcomp.c, but I can't find anything zstd-related in /crypto.
So is zstd for zram actually available in Linux 4.15 or not?
|
It’s supposed to be available in 4.15, as long as the CONFIG_CRYPTO_ZSTD setting is enabled. The implementation lives in lib/zstd.
However the zram integration expects to find zstd via the crypto API, as you discovered, and that part’s missing — which explains why there’s no way to actually enable CRYPTO_ZSTD, and why... | Is zstd for zram actually available in Linux 4.15? |
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I want to use ULOG and send firewall logs to ulogd2
iptables -A INPUT -i eth0 -j ULOG
gives me following error:
iptables: No chain/target/match by that name
I have these LOG-related options enabled in my kernel:
CONFIG_NETFILTER_NETLINK_LOG=y
CONFIG_NF_LOG_COMMON=y
CONFIG_NETFILTER_XT_TARGET_LOG=y
CONFIG_NETFILTER... |
ULOG has been deprecated, and if you don't have module ipt_ULOG you should move on to the newer NFLOG target. ulogd handles both of these, even though it is still called "ulog". Check out man iptables-extensions.
| iptables: No chain/target/match ULOG |
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There are some trivial troubles that always obsess me.My Gentoo always complains 'Could not find the root block device in UUID=5f7c7e13-2a46-4ae4-a8c0-f77f84e80900' and stuck,once I try to boot. However, if I type the same device name /dev/sda2 in, the system goes on.I don´t know why. My Gentoo was installed in on... |
Finally, I figured it out after several days have gone.It is caused by driver problem. My Gentoo is installed in my external hard-disk connected with my laptop by a USB cable.However, the USB Mass Storage Support option wasn't masked build-in when I built my kernel.Hence, it always blocked in that way.If some are in... | Could not find the root block device (in Gentoo) |
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It's interesting to look at the entries in dmesg, but how can I find out what they all mean? I did man dmesg, but I can't find anything about decoding the messages themselves.
I wonder: Is there a way to drill down and find out the meaning and origin of each entry? For example which driver that wrote it (if it was a d... |
There's no easy way. These messages are intended for kernel developers and experienced system administrators, not for ordinary users. There's no general structure to them (apart from the number in brackets, which is the number of seconds since the kernel booted).
You can look for the message text in the kernel source ... | How can I find out what the entries in dmesg means? |
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I have a system freeze issue and I found this discusion on github, one of them suggest to add 5 patches:
When I type:
patch p1 < 0001-PM-autocomplet.patch
It asked File to patch, I don't know what to fill. How can I proceed and apply these patches.
|
To apply a patch of this form:
diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h
index 0f65d36..ff59753 100644
--- a/include/linux/pm_qos.h
with patch -p1, several conditions have to be met.
You have to be in the top-level directory of a kernel source tree. The -p1 option will strip one path component fro... | apply patch when asked `File to patch`, what should I do? |
1,587,375,393,000 |
I have a CentOS 7 headless system with no serial ports. I sometimes want to access the server using a serial cable, so I plug in a USB serial cable (to my laptop's serial port) but I can't get a console/BASH from the connection.
Is there something I have to do to tell the kernel to always create a serial console on a... |
EDIT: This won't work if you have a recent udev version, because udev prevents you from starting long-lived background processes in RUN scripts. You may or may not be able to get around this by prefixing the getty command with setsid but in any case it's discouraged if not outright disallowed. If you have a system whi... | Create serial console on plug in USB serial device |
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I am trying to get a conceptual understanding of the purposes the kernel modules can have.
The motivation for this question was a realization that interface to an actual hardware goes through multiple kernel modules.
For example, the USB gadget driver has multiple kernel modules, where only one is used to actually com... |
What is the reason of implementing this "kernel module stack" structure?
This is the way pretty much all software is written, in modular stacks. Consider your GUI: there's all the kernel space stuff involved including a driver stack, then in userspace you have the X server, and on top of that a window manager, and ... | Using multiple layer of kernel modules for interfacing a hardware device? |
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In Ubuntu 13.10 on my (Dual Core i5 Lenovo G570) laptop, I recently discovered the wonders of indicator-cpufreq, so I can extend my battery life dramatically by setting it to 'ondemand' or 'powersave' governor - here is the menu it shows:
I was wondering whether I... |
This is related to a new driver introduced in Fedora 20 that does not need more than those two governors. See this thread CPU Governors - where is ONDEMAND? for details.
To have the missing governors, you should boot with the kernel parameter intel_pstate=disable.
To do so, in the GRUB boot screen, choose "edit boot... | How to get ondemand governor on fedora |
1,587,375,393,000 |
How do I check that packet socket support has been compiled into my kernel? I'm running Crunchbang, a Debian-based distribution.
|
Most Linux distributions include the config parameters used to compile the kernel in /boot/config-<kernel-version>.
So
grep -x 'CONFIG_PACKET=[ym]' "/boot/config-$(uname -r)"
Should tell you if AF_PACKET socket support is included (m for as a module).
Otherwise, you can just try and create a socket (using socket(2), ... | How do I check if I have packet socket support enabled in my distro's kernel? |
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I've added few modules into mkinitcpio.conf.
Are they automatically loaded at kernel boot or with udev if I don't specify them in modules list in rc.conf?
|
The modules listed in /etc/mkinitcpio.conf are included in the intitrd when it is generated with mkinitcpio -p linux. This loads the temporary filesystem into memory, and needs to include modules necessary to create this successfully, depending on your setup.
An example would be adding raid1 to your modules line in /e... | Do I have to list modules in both `/etc/mkinitcpio.conf` and `/etc/rc.conf`? |
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After I updated my Kernel to version 3.0, i always get this line when my Arch-Linux system is booting up:
Loading User-specified Modules [BUSY] [FAIL]
I have no idea what could cause this to happen. My MODULES-array in the /etc/rc.conf-file looks like this:
MODULES=(fuse wl !b43 !ssb !usblp vboxdrv vboxnetflt)
... |
Blacklisting of modules in the MODULES array is deprecated, as announced here. Perhaps this is the cause.
| Problem at boot-time: "Loading user-defined modules [FAIL]" |
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Am currently running POP_OS 20.04 (LTS). When I open the terminal and run the command,
dpkg --list | grep linux-image
it returns a list of apparently installed images, including my current (6.0.12) and most recent (5.17.5), about nine images from version set 5.0 and six from version set 5.3 ...plus one from 4.18 and ... |
The rc marker at the start of each line indicates that the packages are removed, but configured — i.e. all their contents have been removed, apart from configuration files. Packages in this state don’t appear in Synaptic by default.
You can remove them with sudo dpkg --purge or sudo apt purge, listing the packages you... | How to remove old kernel images |
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I use a Measurement Computing DAQ in Ubuntu to perform continuous analog reads and writes from another system connected to the board. I have been using Ubuntu 16.04 (which went up to Linux kernel 4.15) for about five years now. I was recently exploring upgrading the system to Ubuntu 20.04 - 22.04 and each of those ope... |
I was having the same kind of problem with real-time threads when updating the kernel on my computer. For me sysctl -w kernel.sched_rt_runtime_us=-1 helped.
The change that broke this was: Disable RT_RUNTIME_SHARE by default
| What changed from Linux Kernel 5.9 to 5.10? |
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I use kernel.org docs to read about kernel functions. Now I am trying to make possible reading manuals for kernel-mode functions, such as printk with man 9 printk. The section 9 is used for this purpose: from man man section descriptions:
9 - Kernel routines [Non standard]
Running make mandocs at /usr/src/linux/ thr... |
During May 2017, Linux kernel documentation migrated to use ReST instead of DocBook (commit). During the final steps of that migration, the make mandocs target was removed from kernel Makefile system (commit).
Apparently nobody has missed the manpage format enough to submit patches for a process that would build the k... | Installing man pages for section 9 (kernel routines) |
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I'm working on an embedded system (based on a Cortex-A8 CPU) running Linux kernel 4.19, OpenSSH_8.3p1, OpenSSL 1.1.1h, glibc 2.32, compiled with GCC 10.2 using buildroot.
When a client tries to connect over ssh, the following message is logged to the console, and the client gets disconnected:
[ 120.954119] audit: typ... |
As user414777 commented, the missing syscall is clock_nanosleep_time64. This was originally added to the kernel on the 5.6 branch as part of the solution to the Year 2038 problem, and it was backported to every branch starting with 5.1.
The GNU C Library started utilising these 64-bit time functions in v2.31, and the ... | sshd disconnects after unknown syscall |
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I just stumbled upon a random question that goes like, does the Linux kernel swap out any memory pages even when there are still some available memory spaces? I thought it does not in principle, but the Linux distributions still usually demand a dedicated swap partition when it's installed.
To put this in another way,... |
does the Linux kernel swap out any memory pages even when there are
still some available memory spaces
Check out vim /proc/sys/vm/swapiness (on Ubuntu at least). This specifies how often swaps are done and can imply that swaps are done even when memory is available. The real reasoning to find an optimal value for th... | Does page swapping happen when the main memory is still available? |
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I have written own init process (pid 1) for my system, to improve security I decided to add hidepid=2 while mounting procfs in /proc location (procfs not mounted by default).
After mounting the procfs I ran the mount command to check everything mount fine with given mount option, I noticed hidepid=2 was not listed in ... |
There is a commit in the Linux kernel (https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=69879c01a0c3f70e0887cfb4d9ff439814361e46) that says:
In addition removing the unnecessary complexity of the kernel mount
fixes a regression that caused the proc mount options to be ignored.
Now tha... | Why procfs mount option only working on remount? |
1,562,858,941,000 |
It seems open-vm-tools-dkms was deprecated in Debian 9 (Stretch) and is no longer available in Debian 10 (Buster).
What does this mean — is the functionality obsolete or has it moved to some other package?
|
The package provided the vmxnet driver, which is obsolete and replaced by the vmxnet3 driver which is part of the kernel. This is alluded to in the package description in Stretch:
This package provides the source code for the vmxnet module, which was superseded by vmxnet3. You should only install this package if you ... | What has happened to the package open-vm-tools-dkms in Debian? |
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I cannot launch any program in my desktop environment. I get these errors in dmesg:
traps: terminator[3670] trap int3 ip:374dda71261 sp:388624bbec0 error:0
traps: pcmanfm[3685] trap int3 ip:380699ca261 sp:3e15d350150 error:0
traps: audacious[3687] trap int3 ip:3636d699261 sp:3a18365ccb0 error:0
what do those messages... |
this looks like prroblems caused by filesystem / hdd failure
| unable to launch any program: trap int3 ip error |
1,562,858,941,000 |
I'm trying to manually create my own custom usb drive, with a bunch of iso files on it, and a partition for data. I used the instruction I put here to create my key, but to sum-up, I have done
a partition /dev/sda1 for data
a partition /dev/sda2 that has grub installed
a partition /dev/sda3 that contains my iso files... |
It seems that it isn't grub related or that your conf is at fault; it seems that it is Debian related, based on this article and citing textually:
Now the first time I tried to boot the most recent Debian installer this way, I ran into a bit of a problem. It turns out that the initrd that comes on the ISO itself does... | Manually create grub entry for iso debian file : cannot copy cdrom |
1,562,858,941,000 |
Supposedly I passed the kernel a parameter that it doesn't understand, for example blabla or eat=cake, what would the kernel do with these unknown parameters, the traditional case would be passing any unknown parameter to init, in case if the the Linux kernel starts with early user space (initramfs) would it pass it t... |
From the kernel documentation:
The kernel parses parameters from the kernel command line up to --;
if it doesn't recognize a parameter and it doesn't contain a ., the
parameter gets passed to init: parameters with = go into init's
environment, others are passed as command line arguments to init.
Everything af... | What does the Linux kernel do with unknown kernel parameters? |
1,562,858,941,000 |
I was revising Linux system calls. I found that a few calls are unimplemented system calls. For example: afs_syscall. I don't understand why they are included in man pages if they are not yet available.
They are not implemented in the kernel. So who will implement them? Will they be available in future kernel release... |
Most of them used to be implemented at some point in Linux kernel history time, but some like at least vserver are still implemented in specific kernels.
The majority of these calls is now essentially obsolete but their slot remains and contains a stub which role is not to break old code and allow a re-implementation ... | What are unimplemented system calls? |
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I have checked out linux kernel git repository
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
I know how to use git log, git show and similar commands to see changes/commits in the main kernel tree. For my particular purpose, I am however only interested in changes of the kernel tree 3.18.... |
I would rather clone this git. And then do git diff --stat
$ git clone git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git`
$ cd linux-stable/
$ git diff --stat v3.18.6 v3.18.7
| git: show which files have changed between kernel 3.18.6 and 3.18.7 |
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While i was reading dmesg log just to check that everything is fine, i met
[ 18.956187] [drm] Wrong MCH_SSKPD value: 0x16040307
[ 18.956190] [drm] This can cause pipe underruns and display issues.
[ 18.956192] [drm] Please upgrade your BIOS to fix this.
Looks that it does not cause problems on my laptop, but w... |
Dissecting the acronym, I get that MCH stands for 'Memory Controller Hub' with is an older name for the northbridge. This chip is part of your I/O controller hub.
As for SSKPD, there is not much information I can find other than what is in various intel manuals. Here is a snippet from one of them:
SSKPD — Sticky Scra... | What is MCH_SSKPD warning in dmesg? |
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Is there any proper way to build a minimal kernel for FreeBSD? The FreeBSD Handbook has the lack of information about this. By default /boot/kernel directory has the pretty big size - around 450MB. I want to minimize kernel fingerprint and remove all unnecessary kernel modules and options. Should I use "NO_MODULES" op... |
There are a number of things you can do to reduce the size and number of files in /boot/kernel.
Possibly the best space saving is to be had by setting WITHOUT_KERNEL_SYMBOLS in /etc/src.conf (if this file doesn't already exist, just create it), and the next time you installkernel, the debug symbol files won't be insta... | How to properly build a minimal FreeBSD kernel? |
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I have found a number of examples how to prevent a kernel module from being loaded. One of them is about USB storage module. The next code has been provided:
echo "blacklist usb-storage" | sudo tee -a /etc/modprobe.d/blacklist.conf
then I decided to check the name by lsmod, so I plugged a USB stick in and found it to ... |
The module names may contain both - and _ . Both symbols can be interchanged while using with modprobe or lsmod and also in the conf files in /etc/modprobe.d/ .
So that means you can use any of usb_storage or usb-storage for blacklisting.
| Which kernel module name is currently correct "usb-storage" or "usb_storage"? |
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I am trying to set the oom_adj value for the out of memory killer, and each time I do (regardless of the process) I get back exactly one less than I set (at least for positive integers. I haven't tried negative integers since I want these processes to be killed by OOM Killer first).
[root@server ~]# echo 10 > /proc/1... |
oom_adj is deprecated and provided for legacy purposes only. Internally Linux uses oom_score_adj which has a greater range: oom_adj goes up to 15 while oom_score_adj goes up to 1000.
Whenever you write to oom_adj (let's say 9) the kernel does this:
oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
and stores th... | OOM Killer value always one less than set |
1,562,858,941,000 |
I'm learning Unix from the Unix Architecture book by Maurice J Bach.
My confusion is with the concept of kernel. What is a kernel? I understand it's the operating system and it is a process.
But when my teacher teaches he says a system call(), results in a process going from user mode to kernel mode.
What actually ha... |
What is a kernel?
In the sense of your question, it is a single large program that runs at a special privilege level on the processor. It provides all of the core operating system facilities: multitasking, IPC, file systems, etc. It is also the process that runs the device drivers, which in turn control the computer... | what is a Kernel? [closed] |
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Here is my problem. My laptop has an NVidia Geforce 310 M graphic card. And since kernel 2.6 I had problems with the display. I had to use nomodeset option in the grub, if not my screen will be off when the xorg starts even though my computer is running.
Fortunately, this problem was fixed in early 3.0 kernels. It wa... |
I think this is a tricky question...There's no way we could recommend to update or not without being in same situation as you are right now.
@darnir made a good suggestion, my approach would be really close to it, upgrade but keep your old kernel close enough so you can always go back to it. Either downloading the RPM... | Should I update my Fedora or not? |
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From here: http://fedoraproject.org/wiki/Common_kernel_problems#Can.27t_find_root_filesystem_.2F_error_mounting_.2Fdev.2Froot
A lot of these bugs end up being a broken initrd due to bugs in
mkinitrd.
Get the user to attach their initrd for their kernel to the
bz, and also their /etc/modprobe.conf, or have them... |
An initrd (short for “initial RAM drive”) is a filesystem that's mounted when the Linux kernel boots, before the “real” root filesystem. This filesystem is loaded into memory by the bootloader, and remains in memory until the real boot. The kernel executes the program /linuxrc on the initrd; its job is to mount the re... | Kernel Panic - Can't find root filesystem / error mounting /dev/root |
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Is there anyone that can tell me why, on a preemptive kernel, PAE would not work? This question is an exam question, however I haven't got a clue why it would not work.
|
The clue likely lies here, from O'Reilly's Understanding the Linux Kernel:
"Some real-time operating systems feature preemptive kernels, which means that a process running in Kernel Mode can be interrupted after any instruction, just as it can in User Mode. The Linux kernel is not preemptive, which means that a proces... | Preemptive kernel and Physical Address Extension |
1,562,858,941,000 |
as I've already wrote in the topic, I compiled a new Kernel with make defconfig, the bzImage is where it there, so is vmlinux.bin. I've installed modules with make modules_install.
Now, what is the next step? should I rename bzImage to my liking and put it into /boot? And how do I create an initramfs?
vmlinux.bin is e... |
Once you've made make modules_install, the next steps are:
make install this will take care to move the bzImage, System.map and .config to /boot with the right names, e.g. config-2.6.39-rc1, System.map-2.6.39-rc1, etc...
the next step is to build the initramfs. That depends on the distro. On a debian-like distro, it ... | Compiled a Kernel (2.6.39-rc1), where is the corresponding initramfs? |
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nc -l -u 6666 on the receiving machine gets no messages from netconsole.
tested by doing "echo test > /dev/kmsg"
i am able to connect with netcat by doing "nc -u 10.0.0.192 6666" on the netconsole machine
"sudo tcpdump -i wlp170s0 -n -e port 6666" outputs nothing on the listening machine
netconsole options:
modprobe n... |
Turns out you have to increase the verbosity with dmesg -n 8
| Unable to get output from netconsole |
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Is linux-next going to be the the mainline kernel later? If yes, is it the one first turns out to be RCs and eventually the stable kernel version?
|
Not quite; linux-next is described as
the holding area for patches aimed at the next kernel merge window.
It gives an indication of what’s likely to be in the next release, but a patch’s presence in linux-next doesn’t guarantee that Linus will merge it into the main tree, not does a patch’s absence mean that it won’... | Linux-next kernel version of the kernel tree |
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After a few weeks of not having time for games, today I am unable to launch Steam.
I do not remember some bigger change in the system = Linux Mint 20 than upgrading my Mint today from version 20.2 to 20.3.
Here is dmesg snippet:
$ \dmesg --human --color=auto --ctime
[Fri Jan 7 19:41:33 2022] ------------[ cut here ]... |
The issue got resolved by reverting to Nvidia driver version 470.86.
So, maybe the 495 driver branch is not game-ready yet. In any case, I am leaving the question here for other readers.
| Unable to launch Steam on Nvidia 495 driver, 5.4 kernel, Linux Mint 20.3 |
1,562,858,941,000 |
Quoting the linux kernel documentation for boot parameters :
pcie_bus_perf : Set device MPS to the largest allowable MPS based on
its parent bus. Also set MRRS (Max Read Request Size) to the largest
supported value (no larger than the MPS that the device or bus can
support) for best performance.
I fail to understand... |
I hope you found the answer but I found some information for this which could help.
This kernel-mailing-list-discussion and this article are mentioning this issue and the explanation is that by setting the MRRS you are ensuring that the devices are not sending out read requests where the completion-packet-size (the an... | pcie_bus_perf : Understanding the capping of MRRS |
1,562,858,941,000 |
I am using macOS with SIP enabled. And I am figuring out why the scripts run so slowly with the SIP after a modification or creation.
And I found if I modify a script by editors like vim or nano, and run it by ./script.bash, it will take about 1 second to finish the script for the first time after each modification.
F... |
I found this article which I believe explains your issue.
Apple has introduced notarization, setting aside the inconvenience this brings to us developers, it also results in a degraded user experience, as the first time a user runs a new executable, Apple delays execution while waiting for a reply from their server. ... | What's the difference between writing a file by editor like vim/nano and by output redirection in shell? |
1,562,858,941,000 |
I'm famillar with iptables -F and other features of iptables.
I need to disable iptables from kernel, of course I prefer to disable from sysctl instead of recompiling the kernel.
|
If your kernel uses modules for iptables, which is the case in most distributions, you can blacklist the base module; create a file named, for example, /etc/modprobe.d/iptables-blacklist.conf, containing
install ip_tables /bin/false
You can block other variants in a similar fashion (ip6_tables, ebtables, nf_tables et... | How to disable iptables from kernel |
1,562,858,941,000 |
The default linux kernel config (at least in Ubuntu and Arch) is not as optimized for desktop responsiveness as linux-ck or Zen Kernel. The difference between those kernels and the default one is very noticeable when the CPU or disk load is high.
Is there anyway to make the default kernel better for UI responsiveness... |
A/ It is not the kernel .config which makes your kernel less optimized for desktop responsiveness than linux-ck or Zen kernels.
linux-ck and Zen kernels just use a different scheduler.
B/ Mainline kernel offers many ways to increase desktop responsiveness without the need to patch or reconfig it.
Many tweaks can be ac... | Optimizing Linux for desktop responsiveness without thirdparty kernels |
1,562,858,941,000 |
I am confused about which is the proper formatting to use within mkinitcpio.conf ... I have noticed sometimes double quotes are used and other times parentheses to close off the users desired hooks, modules, etc. settings.
Example:
HOOKS="base udev autodetect block filesystems"
HOOKS=(base udev autodetect block file... |
This is the old style:
HOOKS="base udev autodetect block filesystems"
And this is the current new style:
HOOKS=(base udev autodetect block filesystems)
see also arrayize config vars in mkinitcpio.conf
This change was done in 2017, so you should see the old style only in older installs.
Both styles work so don't worr... | Which format is the correct format to use for mkinitcpio.conf? |
1,562,858,941,000 |
Content of hostname file in my server is:
# cat /etc/hostname
sub.mysite.com
But when I ping my CentOS 7 server it says:
# ping sub.mysite.com
64 bytes from sub ...
Even:
# ping ns1.mysite.com
64 bytes from sub ...
How can I tell my server to have the following output when pinging?
64 bytes from sub.mysite.com ... |
ping doesn't use /etc/hostname to resolve IP to name mappings, it uses the Name Service (netns) to do these translations. Incidentally, /etc/hostname is part of systemd:
$ rpm -qf /etc/hostname
systemd-219-42.el7_4.10.x86_64
That short name you're seeing, sub, is coming from your /etc/hosts file via the Name Service.... | How to change `ping from` value when pinging Linux server? |
1,562,858,941,000 |
How do I get the value of PAGE_CACHE_SIZE that is mentioned in man mount?
man mount:
Mount options for tmpfs
size=nbytes
Override default maximum size of the filesystem. The size is given in bytes, and rounded up to entire pages. The default
is half of the memory. The size
pa... |
Page cache - is the place in RAM where files are stored before writing to disk or after reading from disk. It's reduces delays for I/O operations to/from SSD, HDD, CD ...
tmpfs is the filesystem that lives in RAM permanently so tmpfs lives in page cache.
So page cache lives in RAM and consists of pages.
Page - is the... | How do I get the value of 'PAGE_CACHE_SIZE' that is mentioned in 'man mount'? |
1,562,858,941,000 |
As the options make menuconfig and make nconfig allow a nice way to configure the kernel options, are there any way to get this hierachical structure for print it?
Something similar to the "tree" command ouput.
|
Thanks to the replay of @jeff-schaller I did a contribution to the project Kconfiglib and now there is a new example script for this task. These are the steps to use it:
Inside the directory with the linux source, clone the repo:
root@23e196045c6f:/usr/src/linux-source-4.9# git clone git://github.com/ulfalizer/Kconfig... | Formatted print of linux kernel config |
1,562,858,941,000 |
Lets say my userspace (packages) are compiled with gcc 4.7 and libc6 2.13 (Debian Wheezy)
Can I compile linux kernel under different dev environment, such as gcc 6.3 and libc6 2.24 (ie, under Debian Stretch) ?
I know that unlike packages, kernel is not linked with any dynamic libraries. So theoretically, it should mak... |
As you point out, the C library being used has no impact on the kernel, the kernel doesn’t use the C library. (There’s an indirect impact, since it’s used to build tools the kernel uses during its build process, but that’s extremely unlikely to affect the end result.)
The kernel can be built with a variety of differen... | Does kernel need to be compiled in same dev environment as userspace? |
1,562,858,941,000 |
The Scenario
I'm trying Kernel Programming for Linux, where I've created module, Inserted, Removed and checked it's output in dmesg as well
The Problem
When I have inserted module, I can verify that it is inserted successfully by firing lsmod. Yet, when I fire modinfo it returns an error saying it isn't present there.... |
modinfo by default searches in /lib/modules/<kernel-version>. So you would have to copy your kernel module in a subdirectory in there. Most likely /lib/modules/<kernel-version>/extra.
After copying your module in the right place, you also should execute depmod -a.
| modinfo does not return self inserted module's information |
1,562,858,941,000 |
To configure netconsole you should pass IP-address and MAC-address of destination host. If you don't pass MAC as a parameter - netconsole packs IP packet to ethernet frame with broadcast address as a destination.
Why does netconsole not search for route to host at routing table?
Is it a netpoll limitation?
Or is it fa... |
Netconsole was designed to work as soon as possible after a reboot. From the kernel documentation:
Netconsole was designed to be as instantaneous as possible, to
enable the logging of even the most critical kernel bugs. It works
from IRQ contexts as well, and does not enable interrupts while
sending packets. Du... | Why does netconsole not search for route to logging server? |
1,562,858,941,000 |
After upgrading my CentOS 7 kernel from 3.10.0 to 4.8.7, while rebooting the system I will get the following lines:
[ 0.641455] cpufreq: cpufreq_online: Failed to initialize policy for cpu: 0 (-19)
[ 0.641734] cpufreq: cpufreq_online: Failed to initialize policy for cpu: 1 (-19)
[ 0.641873] cpufreq: cpufreq... |
Are you using virtual machines or a hypervisor? If yes so, you should update your hypervisor host to the latest version so it can support the kernel version.
CPUFreq stands for CPU frequency scaling which enables the operating system to scale the CPU frequency up or down in order to save power.
I'm not sure why you're... | Kernel 4.8.7 failure on cpufreq - CentOS 7 |
1,562,858,941,000 |
ACPI procfs is deprecated in new kernel versions. In sysfs, which is supposed to replace it, I don't know of any clean way to read the state of the lid button. What is the new way of doing this?
|
TL;DR: This exact feature is gone forever, because of laptops' poor quality and buggy precious, proprietary, NDA-ed firmware. But there is a workaround.
According to this thread on Linux kernel bug tracker, firmware in way too many laptops initializes its internal lid state variable to zero on boot - meaning closed. D... | sysfs alternative to /proc/acpi/button/lid/LID/state |
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