date int64 1,220B 1,719B | question_description stringlengths 28 29.9k | accepted_answer stringlengths 12 26.4k | question_title stringlengths 14 159 |
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1,425,951,077,000 |
I encountered this problem a while ago when upgrading my kernel but put off upgrading until now.
On my system I can happily mount network shares using CIFS running kernel 3.7.10, however when I've tried with newer kernels (currently trying with 3.13.1, but have been trying since 3.12.6) I get the following errors when... |
I've finally solved this the solution was to add the ''sec=ntlm'' option for mount.cifs because the default behaviour changed. From
man mount.cifs
...
The default in mainline kernel versions prior to v3.8 was sec=ntlm. In v3.8, the default was changed to sec=ntlmssp.
...
So my /etc/fstab entries now look like...
# ... | mount.cifs : mount error(12) : Cannot allocate memory |
1,425,951,077,000 |
As I understand it, process descriptors are stored in a doubly linked list data structure. But fork can be used to create multiple children for the same process, so that makes me think that there is a tree structure, because multiple processes will point to one parent process. Which is correct? Are process descriptors... |
Your confusion stems from mixing two things: (1) keeping the process descriptors organized, and (2) the parent/child relationship.
You don't need the parent/child relationship to decide which process to run next, or (in general) which process to deliver a signal to. So, the Linux task_struct (which I found in linux/sc... | Internal organization (with regard to family relations) of processes in Linux |
1,425,951,077,000 |
I've built a kernel in tmpfs, then I rebooted.
Now I see a message when I compile the 3rd party module,
NO SIGN [M] XXXX.ko
How can I get it signed? The key pair generated during rpmbuild is lost already I guess
|
This was surprisingly lacking in documentation. I found this file, module-signing.txt, which is part of the RHEL6 Kernel Documentation. In this document it shows how to generate signing keys, assuming you want to sign all your modules as part of a kernel build:
cat >genkey <<EOF
%pubring kernel.pub
%secring kernel.sec... | Sign a module after kernel compilation |
1,425,951,077,000 |
The CFQ IO scheduler supports priorities though I am not sure that Deadline does (I believe not). The premise is that when I renice a task it gets a larger share of CPU under the Completely Fair Scheduler. Since this task is likely to run more often it would call for IO more often as well when needed, correct?
I am wo... |
Disk and memory scheduling are entirely different. In the absence of an IO priority scheduler, IO will be handled on a first come first served basis. If the system is IO bound, then all processes run in a more or less round robin basis until all are waiting for I/O. The nice priority of a process will have little im... | Does IO prioritise by the very nature of renicing a task? |
1,425,951,077,000 |
Based on my research on mmap(), I understand that mmap uses demand paging to copy in data to the kernel page cache only when the virtual memory address is touched, through page fault.
If we are reading files that are bigger than the page cache, then some stale page in the page cache will have to be swapped out reclaim... |
will the page table be updated to map the corresponding virtual memory address to the address of the old stale page in the cache (now containing new data)? How does this happen?
When mmap() is called, it creates a mapping in the process's virtual address space to the file specified. This mapping merely sets up the a... | Does mmap() update the page table after every page fault? |
1,425,951,077,000 |
I'm trying to use a Khepera III robot. The documentation says I need a Linux OS with kernel 2.6.x. An Ubuntu 8 image was provided at the website. When I created a virtual machine with that image, I tried to install the packages I need for using Kheperra III but I couldn't. I tried also to install the updates but I cou... |
Ubuntu 10.04 Lucid Lynx is uses the 2.6.x kernel and the server edition is supported until 2015-04. You can download it here - http://releases.ubuntu.com/10.04/
For more on the differences between server editions and desktop editions of Ubuntu, see this question on Ask Ubuntu.
The main issue seems to be that there is ... | What distribution still supports the 2.6.x kernel? |
1,425,951,077,000 |
I've read in different textbooks that say Linux is light-weight(e.g. It could fit on a 1.4MB floppy). So why is the download from the Ubuntu or Fedora CD sized or larger?
Do the device drivers extend the kernel? For example: if I have new hardware and I have installed the device driver, will my kernel code get extend... |
It's just barely possible to fit an extremely minimal Linux system on a floppy. (Here are a few examples; beware that many of these span several floppies.) With just 1.44MB, there is no have any room for any application; I think you can get a minimalistic command line with no interesting command to run.
As an example ... | Why are Linux installs bigger than I've read? Some beginner questions |
1,425,951,077,000 |
I am using CentOS 7 with "3.10.0-123.4.2.el7.x86_64" version, but I don't know why the kernel threads named flush aren't present in this kernel version.
I tried to look in the kernel change log, but I didn't find anything.
[root@localhost ~]# ps aux | grep flush
[root@localhost ~]# echo $?
1
Without these kernel t... |
There are no more dedicated flush threads anymore.
The Linux kernel has moved on to a worker thread model, where several generic worker threads can handle a variety of different tasks. You will see these in the process list as [kworker/#.##]
Unfortunately this new design makes it a bit difficult to tell exactly what a... | Linux kernel 3.10.0-123.4.2 processes [flush] aren't present |
1,425,951,077,000 |
Several of my coworkers have been building custom kernels for their workstations and servers.
What advantages/disadvantages are there to building a custom kernel?
Why should I build a custom kernel?
|
There are multiple reasons why one may choose to manually compile a kernel. I'll try and list the ones that I can think of, off the top of my head here:
An oft-cited, but often wrong reason is that it will work faster. By customizing the compiler flags for the specific system, you could theoretically create better by... | Why should I build a custom kernel? [closed] |
1,425,951,077,000 |
I don't want to load the kernel module nouveau on my debian box at startup, so I put the following in /etc/modprobe.d/blacklist.conf:
blacklist ttm
blacklist drm
blacklist nouveau
I even did a update-initramfs -u but nonetheless those three modules get loaded each time I boot.
Does anyone know why and how to fix this... |
You can find the answer in the wiki: the idea is that one does not use /etc/modprobe.d/blacklist.conf.
Instead, say you want to blacklist pcspkr. You create a pcspkr.conf file in /etc/modprobe.d and put blacklist pcspkr inside. Then run
depmod -ae && update-initramfs -u
| Excluding kernel modules through /etc/modprobe.d/blacklist.conf does not work |
1,425,951,077,000 |
I ask this only in regards to memory addressing.
I know that a PAE kernel allows the OS to access more memory than a standard 32-bit kernel, however, what are the other implications? What specific differences are there between a 64-bit kernel and a 32-bit PAE kernel?
According to Wikipedia, a processes address space r... |
The kernel sees the physical memory and provides a view to the processes. If you ever wondered how a process can have a 4 GB memory space if your whole machine got only 512 MB of RAM, that's why. Each process has its own virtual memory space. The addresses in that address space are mapped either to physical pages or t... | What is the difference between 32-bit PAE and 64-bit kernels? |
1,425,951,077,000 |
So i am on a debian buster 10 system and i installed virtualbox and i encountered an error which tells me to load some kernel modules manually.
sudo ./vboxconfig
[sudo] password for user:
vboxdrv.sh: Stopping VirtualBox services.
vboxdrv.sh: Starting VirtualBox services.
vboxdrv.sh: You must sign these kernel modules... |
There are three steps involved in signing modules:
create a Machine Owner Key
enroll it
sign kernel modules with it
The first two steps only need to be done once, the last will need to be redone every time the modules are built.
To create a MOK:
openssl req -new -x509 -newkey rsa:2048 -keyout MOK.priv -outform DER -... | Sign Kernel Modules |
1,425,951,077,000 |
It appears that Grub-EFI will only boot a "signed" Linux kernel. Is there some command that will allow me to query a given kernel image to find out what signatures (if any) are present on it?
|
It depends on what kind of signature you're talking about. If you have an EFI system, you can have signed EFI executables (*.efi) and force your EFI firmware to only execute those with a known signature. This is known as Secure Boot. To check an EFI binary for a signature you can use the tool sbverify:
$ sbverify -... | How to query EFI signature |
1,425,951,077,000 |
When configuring the kernel I see an option to add read-write support for NTFS. Then when mounting my NTFS partition I still have to install ntfs-3g and pass ntfs-3g as the type. I thought if I add NTFS support in the kernel then I wouldn't have to install a library for it. Why is it so?
|
The kernel driver is still read only and has no full write support yet, only with many restrictions.
| Why do I need ntfs-3g when I have already enabled NTFS support in the kernel? |
1,425,951,077,000 |
We know that sysctl command can change kernel parameters with :
# sysctl -w kernel.domainname="example.com"
or by directly editing the file in /proc/sys directory. And for persistent changes, the parameters must be written to /etc/sysctl.d/<moduleName>.conf files as:
# echo kernel.domainname="example.com" > /etc/sysc... |
As far as I know, you can use modprobe to adjust parameters only when the feature in question has been compiled as a module - and you're loading the module in the first place. For setting module parameters persistently, you'll have the /etc/modprobe.d directory. (Generally you should leave /usr/lib/modprobe.d for dist... | Difference between modprobe and sysctl -w in terms of setting system parameters? |
1,425,951,077,000 |
What's the maximum allowed number of TTYs?
I found pty.max, but is there anything similar for TTYs? Or is it defined as a fixed value in kernel headers, I couldn't find that
|
In case you're referring Linux virtual consoles as TTYs, their number by default is 64 and this is defined in include/uapi/linux/vt.h inside the Linux kernel source tree. The thing you're looking for is NR_CONSOLES.
| What is the maximum allowed number of TTY, is it defined anywhere in kernel headers? |
1,425,951,077,000 |
I experience relatively often that the partition table of a USB stick or SD card is suddenly no longer recognized by the kernel while (g)parted and fdisk still see it, as do other systems. I can even instruct gparted to do a fsck on one of the partitions but it fails of course because the device files let's say /dev/s... |
For some reason your kernel fails to read the partition table:
[ 8775.030291] end_request: I/O error, dev sdb, sector 0
[ 8775.030300] quiet_error: 30 callbacks suppressed
[ 8775.030306] Buffer I/O error on device sdb, logical block 0
[ 8775.033781] ldm_validate_partition_table(): Disk read failed.
Thus, it can't cr... | Partition table not recognized by Linux kernel |
1,425,951,077,000 |
After reading this question, I was a little confused; it sounds like some daemon reacting by rebooting a system. Is that right? Is it a common occurrence in embedded *nixes?
|
Having a watchdog on an embedded system will dramatically improve the availability of the device. Instead of waiting for the user to see that the device is frozen or broken, it will reset if the software fails to update at some interval. Some examples:
Linux System http://linux.die.net/man/8/watchdog
VxWorks (RTOS)... | What is a "watchdog reset"? |
1,425,951,077,000 |
As I understand it, the Linux kernel has had good support for Intel and AMD CPUs (pretty obvious since your OS installs and runs fine!).
But now that AMD is releasing their new Fusion APUs, is it just a gimmick marketing scheme and can be treated as a CPU by the Linux kernel, or is this APU something new and new kerne... |
Kernel 2.6.38 and above will support AMD Fusion Ontario and Zacate APUs.
| Implications of Linux support for AMD Fusion APUs? |
1,425,951,077,000 |
I need to recompile my kernel on RHEL WS5 with only two changes.
Change stack size from 4k to 8k
Limit usable memory to 4096.
How do I recompile the kernel without changing anything else but these two items?
|
To change only the new values you will need the config the old kernel was build from.
In RHEL you can find this in: /boot/config-$(\uname -r)
Copy this file to the kernel source and change the values you want. Use make menuconfig for a ncurses gui.
For other distributions: If the config option CONFIG_IKCONFIG_PROC was... | Recompile Kernel to Change Stack Size |
1,425,951,077,000 |
I have Linux machine dedicated to serving static contents and PHP pages with Apache. Apache also work as a reverse proxy in a subdomain. I moved the PostgreSQL database to another Linux machine.
Is it safe to disable the OOM killer in the kernel?
|
Probably not.
If the OOM killer is running then it is likely that the OOM killer needs to be run to avoid the machine simple grinding to a halt as nothing, even the kernel, can allocate new memory if needed. The OOM killer exists because it is generally better to have some services fall over due to the killer than the... | Is it safe to disable OOM killer in a web server/reverse proxy? |
1,425,951,077,000 |
I find that centos7.8 is using "net.ifnames=0" without "biosdevname=0" in its kernel parameters, the result seems be same: I got traditional nic name such as eth0.
Just curious, what is the difference of "net.ifnames=0" and "biosdevname=0"?
|
From dell docs:
Biosdevname is a udev helper utility developed by Dell and released under the GNU General Public License (GPL). It provides a consistent naming mechanism for network devices based on their physical location as suggested by the system BIOS.
From manpages
biosdevname takes a kernel device name as an ar... | Linux kernel parameters: what is the difference of net.ifnames=0 and biosdevname=0 |
1,425,951,077,000 |
I was reading through all the things that are run during bootup and have seen that after mounting the rootfs, /sbin/fsck.ext4 is run and after that systemd is run. I was wondering where or how fsck is run, because I was searching for it in the kernel source code and couldn't find it and its not part of the init script... |
Edit 2: checked sources
I've found the ubuntu initramfs-tools sources. Here you can see clearly, the Begin: "Mounting root file system" message is printed first, but in the mount_root function fsck is run before the actual mounting. I have ommited some non-relevant code, just to indicate the order. (If you would inspe... | Where is fsck run? |
1,404,386,586,000 |
I need a specific kernel version to compile it with some additional modules.
When I typing:
uname -r
I get
3.8.0-29-generic
I need this one.
uname -a
Linux "..." 3.8.0-29-generic #42~precise1-Ubuntu SMP Wed Aug 14 16:19:23 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
Where can I find this version? Here https://www.ker... |
You could just use apt to get the source,
check that the file /etc/apt/sources.list contains a line starting with
deb-src
and then use the command:
apt-get update
#if you want to download the source into the current directory use:
apt-get source linux-image-$(uname -r)
#if you want the source to be installed in... | get kernel source code |
1,404,386,586,000 |
When my Ubuntu server starts up, I see a message that says: kernel: [11.895392] init: failsafe main process (631) killed by TERM signal. I would like to know what process this is but I'm not sure where to look. When I search through my syslog and kernel.log, I don't see any evidence of processes starting and being g... |
First of all your message already contains the program name:
kernel: [11.895392] init: failsafe main process (631) killed by TERM signal
This means that the program failsafe with the pid 631 received a TERM signal.
To answer your original question, no most Linux Distributions don't log the pids of created processes ... | Does Linux log when a process is started, and the PID that gets assigned to it? Where can I find that log? [duplicate] |
1,404,386,586,000 |
When installing kernel modules, I have the option to strip out debugging symbols using INSTALL_MOD_STRIP=1. This saves significant disk space.
Does it also save memory? Why should one keep the debugging symbols in the kernel modules?
|
Debugging symbols just add extra information to an executable that helps when running a debugger such as GDB. It lets the debugger recreate the source code from the executable to show you where things such as segfaults occur during runtime.
If you are testing / hacking / making something inter-operate with the module ... | When should I keep debugging symbols in kernel modules? |
1,404,386,586,000 |
The linux kernel documentation claims:
Rootfs is a special instance of ramfs (or tmpfs, if that's enabled),
which is always present in 2.6 systems. You can't unmount rootfs …
On all linux systems I tested (kernel > 2.6 and afaik normal boot procedure, e.g ubuntu 12.04), mount does not show a rootfs entry.
However... |
On old systems, mount may disagree with /proc/mounts
Most of the time you won't see rootfs in /proc/mounts, but it is still mounted.
Can we prove that rootfs is still mounted?
1. On old systems, mount may disagree with /proc/mounts
man mount says: "The programs mount and umount traditionally maintained a list of cu... | Why is there no rootfs file system present on my system? |
1,404,386,586,000 |
I would like to know how can i search for the BSP(Board Specific Packages) sections in the Linux Source code?
All comments are welcomed.
|
A board support package may have pieces spread out in the kernel, but the typical parts are in arch/, and if your board requires drivers that aren't already part of the kernel, there may be some pieces in drivers/.
Each arch/ is set up a bit differently. Arm is an interesting one: look in arch/arm/, you'll see several... | How to find the BSP sections in the Linux source code? |
1,404,386,586,000 |
If one program, for example grep, is curretly running, and a user executes another instance, do the two instances share the read-only .text sections between them to save memory? Would the sharing of the main executable text sharing be done similarly to shared libraries?
Is this behavior exhibited in Linux? If so, do o... |
Unix shares executables, and shared libraries are called shared (duh...) because their in-memory images are shared between all users.
I.e., if I run two instances of bash(1), and in one of them run, say, vim(1), I'll have one copy each of the bash and the vim executables in memory, and (as both programs use the C libr... | Are .text sections shared between loaded ELF executables? |
1,404,386,586,000 |
I'm currently having to recompile my wireless driver from source every time I get a new kernel release. Thinking it would be awesomely hackerish to automate this process, I symlinked my Bash build script to /etc/kernel/postinst.d. I've verified that it does, in fact, run when the latest kernel update is installed, but... |
This is no actual answer to your question, just a pointer to a tool that might be related and helpful:
Do you have dkms installed? (Some information here, the alioth page seems down at the moment.) It's supposed to do just that, if I'm not misled. It requires the appropriate linux-headers package and the module/firm... | Running a script every time a new kernel is installed |
1,404,386,586,000 |
Using either NetworkManager or Wicd to manage wireless networking on my Wi-Fi-powered laptop, too often I get randomly disconnected, and I see these messages on /var/log/syslog:
Dec 10 05:21:26 debian dhclient: DHCPREQUEST on wlan0 to 10.0.0.2 port 67
Dec 10 05:21:26 debian dhclient: DHCPACK from 10.0.0.2
Dec 10 05:21... |
This is a known bug with the iwlagn driver. Updating the driver and/or firmware may fix your issue:
https://bugs.launchpad.net/linux/+bug/200509
| Wi-Fi constantly disconnects |
1,404,386,586,000 |
I know that it's possible to extract from a linux kernel the embedded initramfs cpio. I want to know if the reverse operation is possible; i.e., given both a compiled kernel and initramfs archive, how does one combine them?
I'm trying to achieve the same effect of this kernel config...
CONFIG_EFI=y
CONFIG_EFI_STUB=y
.... |
Here is my solution:
you can create a combined .efi image
with kernel, command line and initramfs inside,
called a "unified kernel image".
Reference: Preparing a unified kernel image – ArchWiki.
You might want to focus on the “Manually” subsection.
| How to combine linux kernel and initrd without compiling? |
1,404,386,586,000 |
I'm trying to understand the Debian "booting from Hard Disk" installation manual.
The process is as follows: I copy a kernel image, a ramdisk initrd and an ISO with installer to the hard drive and then configure GRUB to start the kernel and ramdisk, but also I have to tell GRUB, where is the root filesystem (it should... |
Copied from frostshutz comment:
the initrd.gz (initramfs) contains the busybox userland and Debian scripts written to that purpose. GRUB2 also supports loop mounting ISO directly, but usually just to grab the kernel/initrd from the ISO itself, and once that's loaded again the ISO has to be found and loopmounted by th... | How to specify an ISO as the location of root filesystem for GRUB? |
1,404,386,586,000 |
When booting NetBSD, the old Tecra 720CDT that I have, works quite nicely in 1024x768x15 mode with vesa fb.
I always have to activate VESA when booting the system:
> vesa on
> vesa 0x116
> boot netbsd
Now, I was able to somewhat automatize this process by editing /boot.cfg:
menu=Boot normally:rndseed /var/db/entropy-... |
AFAIK, editing /boot.cfg is the preferred method. You can even specify more human-readable modes; I am using (on -current, 7.99 in a VirtualBox VM)
menu=Boot normally:rndseed /var/db/entropy-file:;vesa 1024x768x32; boot netbsd
I think having this in the kernel somehow without it being compiled in would be bad - if y... | How to enable VESA framebuffer as default in NetBSD 6.1 |
1,404,386,586,000 |
I have an Marwell Kirkwood ARM-based NAS server Zyxel NSA 310. I compiled my own 3.8 kernel and enabled ZCACHE, but I still see 256 MB of RAM. I am not sure if GNU free utility should show extra amount of RAM. How do I find out it is really working? Do I need to do some extra steps to make use of it? I have added "zca... |
zcache is buried inside the ram and not easily visible with current tools. To see details you need to mount debugfs and look in /sys/kernel/debug/zcache where there are a whole bunch of statistics, more than you could ever want. The frontswap is reported as pers_* (for persistent) and cleancache as eph_* (for epheme... | How do I determine ZCACHE works on my box? |
1,404,386,586,000 |
I have the following output from running lspci -vv -s 00:00 on my single board computer running Linux.
07:05.0 RAID bus controller: Adaptec AAC-RAID (Rocket) (rev 03)
Subsystem: Adaptec ASR-2230S + ASR-2230SLP PCI-X (Lancer)
Control: I/O- Mem+ BusMaster+ SpecCycle+ MemWINV+ VGASnoop-
ParErr- Stepping- SERR+ FastB2B-
... |
lspci show the info about your PCI devices (depending on options), you can check the man page for futher info.
Regarding the REGION header on the output, these lines details where is allocated the registers used for this component. It is related with the memory mapping and how the memory is used for each component.
Re... | Would someone please explain lspci -vv output? |
1,404,386,586,000 |
I have been struggling with this issue for a while and have done an exhaustive search for answers here and elsewhere before posting this question.
On my Asus X101H, the touchpad is not recognized as a touchpad. I have noticed that this problem does not only occur with my netbook, or Asus netbooks, but a whole host of ... |
Try running sudo modprobe -r psmouse and report how it went. It solved issue for me. If you want to enable it again run sudo modprobe psmouse proto=imps, also you can make a simple script with these commands that controls enabling/disabling touchpad this way.
| Asus X101H - Touchpad not recognized (want to disable while typing) |
1,404,386,586,000 |
Wikipedia says that current Debian 8.2 Jessie is based on kernel
3.16.0, so I was wondering when a native version based on kernel 4.x
would be released and if the live kernel patching will be there as
feature with the 4.x.
I searched for a Debian roadmap on Google, but I found nothing about
the kernel.
|
While it is still not a given, officially most probably the last quarter of 2016, with the release of Debian 9. In the meanwhile, you can start using testing, compile it yourself or using a version compiled by someone else. I am using armbian in a Raspberry Pi like-device (Lamobo R1), which is Jessie, and using a v4.x... | When will Debian switch to Linux 4.x? ( and support the live kernel patching ? ) |
1,404,386,586,000 |
I'd like to upgrade my kernel to try to fix a persistent issue I have with intermittent freezing.
I've tried manually installing the kernel, but it throws errors during configuration and then upon sudo apt upgrade it shows:
linux-headers-5.16.0-051600-generic : Depends: libssl3 (>= 3.0.0~~alpha1) but it is not install... |
WARNING: the below method may break your system. You have been warned.
Ubuntu mainline kernel 5.15.7+ and 5.16 bumps the requirement from libssl1.1 (>= 1.1.0) to libssl3 (>= 3.0.0~~alpha1).
You can find the change from the header packages:
dpkg -I linux-headers-5.15.6-051506-generic_5.15.6-051506.202112010437_amd64.de... | How to use 5.16 kernel with Ubuntu 21.10? |
1,404,386,586,000 |
I using Debian (Wheezy) with the 3.2.0-4 amd64 kernel version and want to upgrade my kernel to newest version, like 3.13.3 stable, but I have no internet connection to my Debian OS. I have installed both of "usb-modeswitch" and "usb-modeswitch-data" packages but Debian doesn't detect my 3g-modem-usb dongle.
I've downl... |
The easy way: backports
I assume you need the new kernel to get your modem to work. If you can live with 3.12 instead of 3.13, at least for now, then instead of recompiling the kernel from source, you can just use Debian Backports. [update: Now backports is up to 3.14]
You can manually grab the package from packages.d... | How do I upgrade the Debian Wheezy kernel offline? |
1,404,386,586,000 |
Is it true that a single application can not allocate more than 2 GiBs even if the system has GiBs more free memory when using a 32-bit x86 PAE Linux kernel? Is this limit loosened by 64-bit x86 Linux kernels?
|
A 32-bit process has a 32-bit address space, by definition: “32-bit” means that memory addresses in the process are 32 bits wide, and if you have 232 distinct addresses you can address at most 232 bytes (4GB). A 32-bit Linux kernel can only execute 32-bit processes. Depending on the kernel compilation options, each pr... | How much RAM can an application allocate on 64-bit x86 Linux systems? |
1,404,386,586,000 |
Writing to a custom character device using
cat 123 > /dev/chardev
gives
cat: write error: Invalid argument
I have changed the permissions to 666 and even tried it with sudo. Still the same results.
Also tried echo in similar way
I use Arch linux 4.8.
Edit: The code for the driver
#include <linux/module.h>
#includ... |
In the kernel, each driver provides a series of methods for the various operations that can be performed on a file: open, close, read, write, seek, ioctl, etc. These methods are stored in a struct file_operations. For devices, the methods are provided by the driver that registered that particular device (i.e. that par... | cat: write error: Invalid argument |
1,404,386,586,000 |
I'm completely confused about explanation of virtual memory in TLDP:
http://www.tldp.org/LDP/tlk/kernel/processes.html#tthFtNtAAB
They say:
Each individual process runs in its own virtual address space and is not capable of interacting with another process except through secure, kernel managed mechanisms.
"Own vir... |
Linux as well as Windows, work pretty much the same here. Every process gets it's own "virtual" address space. This doesn't mean that the memory is actually physically available (obviously most 32bit computers never had enough memory), that's, why it's virtual.
Also the addresses used there don't correspond to the phy... | Misleading explanation of Virtual Memory in TLDP |
1,404,386,586,000 |
I know that Linux OS's are typically multi-programmed, which means that multiple processes can be active at the same time. Can there be multiple kernels executing at the same time?
|
Sort of. Check out User-mode Linux.
| Can there be multiple kernels executing at the same time? |
1,404,386,586,000 |
In short:
How to extract the VERSION, SUBVERSION and PATCHLEVEl numbers from a system backup .img? ideally without root permissions.
Extended:
From the following page:
https://www.raspberrypi.org/downloads/raspbian/
It is provided a Debian zip extracted as .img, which represents a full system backup of a Debian/Raspia... |
This seems to work on the 2017-09-07-raspbian-stretch-lite.img image at that site:
$ sudo kpartx -rva 2017-09-07-raspbian-stretch-lite.img
add map loop0p1 (252:19): 0 85622 linear 7:0 8192
add map loop0p2 (252:20): 0 3528040 linear 7:0 94208
$ sudo mount -r /dev/mapper/loop0p1 mnt
$ LC_ALL=C gawk -v RS='\37\213\10\0' ... | How to extract the linux version from a `.img` backup? |
1,404,386,586,000 |
The book 'Understanding Linux Kernel' says that 'for something abstract such as math functions, there may be no reason to make system calls'. Can any one please explain how is a system call not required in math functions? Isn't the CPU involved in mathematical operations? Can anyone give an example of such a program?
|
I don't have that book to check, but I assuming its using the normal meaning of system calls, then a system call is a call into the kernel to perform some operation the hardware considers privileged, or is unaware of. This is used to enforce permissions, etc. on the system. So you need to make a system call to (among ... | API with no system calls |
1,404,386,586,000 |
Over the past few years, various live kernel patching techniques have become popular among sysadmins who strive to ensure the highest possible uptimes for their systems.
For that process to be possible, a human being prepares custom patches, which are then typically distributed to paying customers, and - sometimes - f... |
We like to think of running programs like the static source code that creates them. But they are really continually changing. Likewise the kernel in memory is NOT the same as the kernel on disk.
To quote Dijkstra in his letter "goto considered harmful"...
My first remark is that, although the programmer's activity ... | Why can't entire kernels be patched live? |
1,404,386,586,000 |
I am trying to upgrade my fedora system (21 → 22) using fedup. I removed all old kernels using package-cleanup but fedup still needs 2MB more on /boot.
These are the files in /boot:
-rw-r--r--. 1 root root 153K Sep 22 17:52 config-4.1.8-100.fc21.x86_64
drwxr-xr-x. 4 root root 1.0K May 25 09:38 efi
-rw-r--r--. 1 root ... |
The vmlinuz-0-rescue-* and initramfs-0-rescue-* files can be safely removed with rm. They're not owned by any package, and to my knowledge there isn't any tool for deleting them (although you can create new ones with dracut).
After removing, run
grub2-mkconfig -o /boot/grub2/grub.cfg
to regenerate your grub config s... | Removing the rescue image from /boot on fedora |
1,320,588,194,000 |
My immediate objective is to compile a small kernel for my laptop without sacrificing usability. I am familiar with the kernel compilation steps (don't necessarily understand the process). What are the options I can get rid of in menuconfig for a faster, slimmer kernel? I have been using the trial and error method, i.... |
Unchecking filesystems and drivers isn't going to reduce the size of the kernel at all, because they are compiled as modules and only the modules that correspond to hardware that you have are loaded.
There are a few features of the kernel that can't be compiled as modules and that you might not be using. Start with Ub... | Stripped down Kernel for a Laptop |
1,320,588,194,000 |
In the Linux Kernel CONFIG_NO_HZ is not set. But an initial reading suggests that setting that option would be nice from a performance point of view. But reading some posts like this made me think again.
Why CONFIG_NO_HZ is not set by default or why no performance improvement when it is enabled?
|
The performance improvement is not visible to everyone, just certain users for which RT kernels really matter : DSP, audio/video processing, and so on. So that config option is not universally beneficial, hence disabled.
| Why CONFIG_NO_HZ is not set by default |
1,320,588,194,000 |
How to enable Ethernet over USB support in Linux kernel?
Which driver (like CONFIG_USB_USBNET) is related to this support?
Is EEM (Ethernet Emulation) regarding this support or not?
|
You need CONFIG_USB_USBNET together with whatever CONFIG_USB_NET_* module you need for your USB device.
The only thing I can find in my config that could match your EEM is CONFIG_USB_NET_CDC_EEM but I don't have that enabled, that is another USB device that I don't own.
| Enabling ethernet over USB support in Linux kernel |
1,320,588,194,000 |
I am compiling an image for wifi devices using OpenWrt. Following the instruction I copy a simple .config file to TOP-DIR.
CONFIG_TARGET_ar71xx=y
CONFIG_TARGET_ar71xx_generic=y
CONFIG_TARGET_ar71xx_generic_XXX_OpenWrt_Router=y
Then run the command make menuconfig. The outcome of this command is
.config file now havi... |
OpenWrt stores config in the directory
target/linux/<target system>/<subtarget>/profiles
You can set target system and subtarget with command make menuconfig:
In my case:
target system = ar71xx
subtarget = generic
So the directory would be:
target/linux/ar71xx/generic/profiles
In this directory, you will find some ... | Where does make defconfig get its configuration in OpenWrt? |
1,320,588,194,000 |
What does it mean to install a new version of the kernel. My Linux box gave me this message when I was updating,
NOTE, 3.8.13 was the last maintained maintenance release by Greg Kroah-Hartman.
It is recommend to move on to linux310-series.
What I want to know is,
Is it really that simple to only change the Linux... |
Yes.
Yes, sort of. It's not simple and it's not "just" an executable file, but you can swap between Linux kernels super easily. This is not applicable to every kernel, though, meaning that e.g. you can probably replace a FreeBSD kernel with a newer FreeBSD kernel, and as stated above, you can upgrade a Linux kernel p... | What does it mean to install a kernel? |
1,320,588,194,000 |
init is the first task executed after kernel is loaded, right?
Then who is its owner.
also I can see [swapper/0] [swapper/1] ..... [swapper/7] having pid 0
PID PPID CPU TASK ST %MEM VSZ RSS COMM
0 0 0 c180b020 RU 0.0 0 0 [swapper/0]
0 2 1 f7550ca0 RU 0.0 0 ... |
init is a user-space process that always has PID=1 and PPID=0. It's the first user-space program spawned by the kernel once everything is ready (i.e. essential device drivers are initialised and the root filesystem is mounted). As the first process launched, it doesn't have a meaningful parent.
The other 'processes'... | init: is it a user thread or a kernel thread? |
1,320,588,194,000 |
I'm in a situation where I have a 10/100/1000-capable PHY cabled only to support 10/100.
The default behaviour is to use the autonegociation to find the best mode.
At the other end, using a gigabit capable router ends in a non-working interface. I guess autonegociation never converges.
I've heard some people tried wit... |
The thing with autonegotiation is that if you turn it off from one end, the other side can detect the speed but not the duplex mode, which defaults to half. Then you get a duplex mismatch, which is almost the same as the link not working. So if you disable autonegotiation on one end, you practically have to disable it... | Remove SOME advertised link modes with ethtool |
1,320,588,194,000 |
As I understand it, part of the Unix identity is that it has a microkernel delegating work to highly modular file processes. So why is Linux still considered "Unix-Like" if it strays from this approach with a monolithic kernel?
|
I believe the answer lies in how you define "Unix-like". As per the wikipedia entry for "Unix-like", there doesn't seem to be a standard definition.1
A Unix-like (sometimes referred to as UN*X or *nix) operating system
is one that behaves in a manner similar to a Unix system, while not
necessarily conforming to o... | Why is Linux "Unix-like" if its kernel is monolithic? |
1,320,588,194,000 |
I read in a book written by Robert Love that:
Linux supports the dynamic loading of kernel modules.
He said this is the difference between Linux and Unix, but I seem to recall there is also KLD in FreeBSD? So can KLD also be seen as dynamic loading of kernel modules?
|
KLD is indeed dynamic kernel modules. In fact, many old school Unixen also have loadable kernel modules nowadays. Your book must be quite old :)
| "Linux supports the dynamic loading of kernel modules. " |
1,320,588,194,000 |
One of my (several) USB drives are reporting this error in dmesg
usb 5-1: device descriptor read/8, error -110
How do I find out the /dev/sdX name of all my USB devices?
In reverse: How do I find out the USB number of a device, given it's /dev/sdX name?
UPDATE:
Many excellent answers given here. I would expect this i... |
I did some testing with USB mass storage devices (USB pendrives and USB connected SSDs) in my computer and think the output of
find /sys/ -name dev -path '*usb*block*'
can help you match the USB number of a device with its /dev/sdX name.
Another method is to match lsblk and lsusb command lines and to identify them v... | How to get a USB device Name from its Number |
1,320,588,194,000 |
I know there's *.conf file in /usr/lib/sysctl.d and/or /etc/sysctl.d folders ready to establish kernel parameters on boot. But they are general;
what I want is to customize some of these parameters (say, net.ipv4.icmp_echo_ignore_all) depending on the user who is in, but I want per-user kernel parameters.
Is it possi... |
What @Tomasz says it's true: those are kernel parameters, so they are "unique"!
Anyway, you can achieve some result with that limit
...in the OP, @Osqui doesn't say users are simultaneously logged in...
by sketching out a script executed when users login/logout using the sysctl command
| Customize sysctl parameters by user |
1,320,588,194,000 |
I have an embedded Linux on some network device. Because this device is pretty important I have to make many network tests (I have a separate device for that). These tests include flooding my device with ARP packets (normal packets, malformed packets, packets with different size etc.)
I read about different xx-tables ... |
What xx-tables is the best to filter (limit, not drop) ARP packets?
iptables
iptables starts from IP layer: it's already too late to handle ARP.
arptables
While specialized in ARP, arptables lacks the necessary matches and/or targets to limit rather than just drop ARP packets. It can't be used for your purpose.
ebta... | Best way to filter/limit ARP packets on embedded Linux |
1,320,588,194,000 |
Today pretty much all kernels use virtual memory provided by the MMU. They do that with the global page table, the address of which is located in a CPU register, and a page supervisor/mapper of pages to processes. The "vm" in vmlinuz, for example, means that the linux kernel supports virtual memory.
All that is poss... |
Virtual memory is almost a decade older than Unix: there was one in the Burroughs B5000 in 1961. It didn't have an MMU in the modern sense (i.e. based on pages) but provided the same basic functions. IBM System/360 Model 67 in 1965 (still older than Unix) had an MMU. Intel x86 processors didn't get an MMU until the 80... | How the original unix kernel adressed memory? |
1,320,588,194,000 |
Unfortunately, when a hard drive (usually a virtual drive) is slow, Linux aborts requests to that drive after a timeout, possibly causing data corruption.
Last time this happened to me, I had 2 vms running (Linux and FreeBSD) on a storage, which had connectivity issues and was frozen for over an hour. The storage itse... |
I have found a timeout, which appears to have a default of 30 seconds on most systems. I'm not completely sure that this is the relevant timeout, but I've increased it on some vms, put the system under a significant load and I've not had any hdd timeouts in the vms so far.
Also, some of the comments are expressing con... | Can the hard drive timeout be disabled in Linux (attempting task abort) |
1,320,588,194,000 |
I have an Android TV stck
I compiled Linux for IT from https://github.com/Galland/rk3x_kernel_3.0.36
But when I booted that Image I found /proc/config.gz is of 0 bytes
can some please explain how the command line params from .config file in kernel source get mounted to /proc.
I mean what goes in the background??
|
Files in /proc do not have a file size in general, and are shown as having 0 size in ls -l, but you can read data from them anyway (see man 5 proc).
Try, for example:
zcat /proc/config.gz | wc
or:
$ ls -l /proc/cmdline
-r--r--r-- 1 root root 0 Aug 4 10:16 /proc/cmdline
Looks empty. But:
$ cat /proc/cmdline | wc
... | /proc/config.gz is of 0 bytes |
1,320,588,194,000 |
I was looking for a list of keyboard scancodes in the linux kernel sources, but I did not find anything. Does someone know where to find these? Especially the USB scancodes would be interesting.
|
The keycodes are in [src]/drivers/tty/vt/defkeymap.map:
# Default kernel keymap. This uses 7 modifier combinations.
[...]
See also my answer here for ways to view (dumpkeys) and modify (loadkeys) the current keymap as it exists in the running kernel.
However, those are a bit higher level than the scancodes sent by th... | Where in the linux kernel sources can I find a list of the different keyboard scancodes? |
1,320,588,194,000 |
I have used buildroot to successfully create a kernel, root file system and cross-compilers to enable me to write application code to run on an embedded device. Currently I have no need to write device drivers and currently have no idea how to go about it anyway but it is quite likely that in future I may need to do t... |
3.x is just continuation of 2.x - at one point Linus decided that the "x" part of the version is too big. Generally you probably want reasonably recent kernel, probably one marked as "longterm". A lot also depends on your application as well - while remote security holes in kernel are rather scarce, local problems are... | What considerations need to be made when choosing the version of kernel for an embedded device? |
1,320,588,194,000 |
I need to install my linux headers for an Nvidia driver install. But I get an error when doing so:
peter@peter-deb:~$ sudo apt-get install linux-headers-$(uname -r)
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package linux-headers-2.6.32-5-amd64
... |
Ubuntu doesn't ship an AMD64-specific kernel header package.
What you probably want is linux-headers-2.6.32-5-generic. This combines Linux headers for both 32- and 64-bit Intel x86 CPU variants.
Say apt-cache search linux-headers to see your other choices.
| Command to install linux headers fails |
1,320,588,194,000 |
I recently deleted my active Linux kernel and continued using the system as if nothing drastic happened. Are there any side-effects to deleting the Linux kernel that's currently in use? What about other non-Windows kernels?
|
The Linux kernel is completely loaded into RAM on boot. After the system is booted, it never goes back and tries to read anything from that file. The same goes for drivers, once loaded into the kernel.
If you deleted the only kernel image on disk, the only consequence is that the system cannot be successfully rebooted... | What potential ills can be brought by 'deleting' a live kernel? |
1,320,588,194,000 |
I have Ubuntu 10.10 and after few updates the boot menu lists many kernel versions. How do I remove older versions?
|
Check for currently-installed kernels:
$ dpkg --get-selections | grep linux-image
linux-image-2.6.38-2-686-bigmem install
linux-image-2.6.32-5-686 install
Check what current kernel you are running:
$ uname --all
Linux debian 2.6.38-2-686-bigmem #1 SMP Thu Apr 7 06:05:53 UTC 2011 i686 GNU/Linux... | grub shows multiple kernel versions on startup |
1,320,588,194,000 |
I was reading "Linux device drivers, 3rd edition" and don't completely
understand a part describing interrupt handlers. I would like to clarify:
are the interrupt handlers in Linux nonpreemptible?
are the interrupt handlers in Linux non-reentrant?
I believe I understand the model of Top/Bottom halves quite well, and... |
The Linux kernel is reentrant (like all UNIX ones), which simply means that multiple processes can be executed by the CPU. He doesn't have to wait till a disk access read is handled by the deadly slow HDD controller, the CPU can process some other stuff until the disk access is finished (which itself will trigger an i... | re-entrency of interrupts in Linux |
1,320,588,194,000 |
ps(1), with the -f option, will output processes for which there is no associated command line in square brackets, like so:
UID PID PPID C STIME TTY TIME CMD
root 1 0 0 Aug28 ? 00:07:42 /sbin/init
root 2 0 0 Aug28 ? 00:00:01 [kthreadd]
root 3 2 0 A... |
Under Linux, ps and top handle information made available by the kernel in /proc, for each process, in a directory named after the pid. This includes two files, comm and cmdline; comm is the process’s command name, and cmdline is the process’s command line, i.e. the arguments it was provided with (including its own “n... | Are processes in square brackets scheduled in the same way as other processes? |
1,320,588,194,000 |
I'm running Arch Linux with systemd boot. In /boot/loader/entries/arch.conf I currently specify the luks crypto device with a line like this:
options rw cryptdevice=/dev/sda1:ABC root=/dev/mapper/ABC
I know I can also use UUID instead of /dev/sda1. In that case the kernel options line would look like this:
opt... |
If you're already using the new LUKS2 format, you can set a label:
For new LUKS2 containers:
# cryptsetup luksFormat --type=luks2 --label=foobar foobar.img
# blkid /dev/loop0
/dev/loop0: UUID="fda16145-822e-405c-9fe8-fe7e7f0ddb5e" LABEL="foobar" TYPE="crypto_LUKS"
For existing LUKS2 containers:
# cryptsetup config --... | How to specify cryptdevice by label using systemd boot? |
1,320,588,194,000 |
I have a USB Linux Kernel module that compiles and builds. Running insmod loads my module and dmseg and tail -f /var/log/debug shows me it works as expected.
Running depmod -a then modprobe from the terminal loads the module and modprobe -r unloads and I see - tail -f /var/log/debug output as expected.
When I plug in... |
You are missing with usb_register and probe functions
Here is updated device driver with usb_register and probe functions
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/usb.h>
#include <linux/usb/input.h>
#include <linux/hid.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Aruna Hewapathirane");
MODULE_... | usb kernel module does not load on demand but works fine with insmod and modprobe from the shell |
1,320,588,194,000 |
I'm into something about writing a "Mock GPU driver" for *nix based systems. What I mean is that, simply I want to write a driver (Behind X-server obviously) to answer X's API calls with some debugging messages.
In other words I want to fool *nix system about having an actual GPU. So I can make a test-bed for GUI-acce... |
Given your requirements, it seems likely to me that you may not need to write your own driver. You may be able to use llvmpipe, which I believe conforms to your requirements. In particular, it is a "real driver" by some meanings of the word, and it does not require that X11 be running.
llvmpipe creates what might be c... | Writing a driver to fool *nix systems about having a GPU |
1,320,588,194,000 |
I have been looking through the documentation for /proc and the "stack" object being a new'ish object in proc, I have also looked through the kernel commit to create it -- however the documentation does not detail exactly what is in the /proc/self/stack file -- and since I intuitively expected it to be the actual stac... |
The file /proc/$pid/stacks shows kernel stacks. On your system, memory addresses of the form ffffffff8xxxxxxx are in the space that's reserved for the kernel. There's not much documentation, you can check the source code. In contracst, the pstack program shows user-space stacks (using its knowledge of executable forma... | What is the difference between /proc/self/stack and output from pstack? |
1,320,588,194,000 |
I am using ssh to remotely access some machines. These machines have a custom kernel installed (based on the 2.6.28 source). However, whenever I try to reboot the machines using sudo reboot, the system uses kexec and loads the 2.6.28-19-generic kernel, which is also intalled on the machine.
So how can I specify which ... |
Normally, when you reboot, the machine will return to grub and either allow you to select a kernel via the keyboard, or boot the default configured kernel. However if you have kexec-tools installed, the reboot command will short circuit this behaviour and directly kexec into a kernel. You can disable this behaviour, a... | Which kernel does reboot load? |
1,320,588,194,000 |
I would like to debug a loaded kernel module I don't have the source code to; I suspect it's a virus. Is there a way to feed it into GDB for analysis?
|
From a debugging perspective, the kernel is a special "process", distinct from the user space processes, which communicate with the kernel via a sort of rpc mechanism (syscalls) or mapped memory..
I don't think you can see the kernel's data structure simply by inspecting some random user process.
Another problem is,... | How to debug an inserted kernel module? |
1,320,588,194,000 |
I am trying to install kernel headers version 4.14.71-v6 (uname -r) for Kali Linux. I already did the common commands...
apt update
apt upgrade
apt dist-upgrade
apt install linux-headers-generic
alt install linux-headers-$(uname -r)
...with and without option -y
Also did reboots. I searched the repos by apt search 4.... |
You are not finding the headers for your kernel version, in the official distribution repository, because you are dealing with a Kali setup using a custom made kernel version.
Whist we do not have all data, from you uname -r, it leds me to suspect it was made using these scripts/tools https://github.com/Re4son/re4son-... | Kali Linux kernel headers for 4.14.71-v6 |
1,320,588,194,000 |
When installing a kernel in Ubuntu(e.g. http://kernel.ubuntu.com/~kernel-ppa/mainline/v4.0-vivid/), what are the files for respectively:
linux-headers-4.0.0-xxx_all.deb
linux-headers-4.0.0-xxx-generic_xxx_i386/amd64.deb
linux-image-4.0.0-xxx-generic_xxx_i386/amd64.deb
linux-headers-4.0.0-xxx-lowlatency_xxx_i386/amd6... |
Debian (and Ubuntu and other derivatives) divides Linux kernel packages into several parts:
linux-image-VERSION-PATCHLEVEL-FLAVOR contains the kernel image that is loaded by the bootloader, a file containing the symbol table (used by some system tools), a file containing the kernel configuration (informative for the ... | What are the deb files for installing a kernel for? |
1,320,588,194,000 |
I have a machine running Debian stable, and I'd like to update the stock kernel to the latest kernel available in the backports repository. There are many kernel-related packages and virtual packages--what is the right way to do this and get the appropriate packages upgraded?
|
Use a meta package (e.g. linux-image-2.6-686), depending on which you want to use. This is so that if the real package name changes (which is very often), you won't lag behind. To determine which meta package to use, have a look at the name of the kernel package you are running. Also, do read the package descriptions ... | How to update Debian kernel to latest in backports |
1,320,588,194,000 |
I am looking for a formal description of the following boot parameters in the linux kernel:
real_root
cdroot
I have problems tuning them to create my own bootable LiveUSB system. Are they specific to my distribution (Gentoo)?
They do not appear in the gitweb kernel documentation.
|
root is the device you want to be mounted up as the root file system when the kernel first starts. This is pretty self explanitory, but it gets complicated because this can actually change over time. The usual reason that happens is when the kernel doesn't have the modules it needs to mount the root file system. In t... | description of linux kernel boot parameters 'real_root' and 'cdroot' |
1,320,588,194,000 |
we have linux DB server redhat 7.2
we notice about many message as below about all disks that are mounted
from /var/log/messages
what we are need to understand if this behavior is relevant to HW problem
Mar 29 13:28:22 server_DB kernel: Buffer I/O error on device sdb, logical block *N4980*
Mar 29 13:28:22 server_DB k... |
This I/O error message is written to warn about a hardware error with sdb. It could be with the disks or with the cable, for example.
I suppose it is less likely to be an error in the disks themselves, if you have a large number of disks all showing errors at the same time :-). It could be an error in the disk contr... | "kernel: Buffer I/O error on device" - Does my server have a hardware problem? |
1,320,588,194,000 |
Suppose I called kmalloc and didn't free that memory before rmmod was called on the module, what happens to that memory? Is it a memory leak and it is completely unusable until restart, or does the kernel free that memory automatically?
thanks
|
It won't be freed until explicitly done. Memory allocated with kmalloc() needs to be freed using kfree(). That piece of memory stays till the system is on.
[...] didn't free that memory before rmmod was called on the module [...]
When you do rmmod, module_exit() will be executed where you can free the memory incase... | What happens to memory that wasn't freed in a kernel module after unloading? |
1,320,588,194,000 |
I am trying to understand the logs of sysdig. It mentions there file descriptors other than 0 (standard input), 1 (standard output), 2 (standard error); file descriptors such as 3, 6, 7, -2 are listed.
If these are the file index or file number in memory, why there are negative numbers?
The structure of the events is ... |
When you use open() to open a file (see man 2 open), you get a file descriptor back for it (it's an int in C). The standard streams are associated with descriptors 0, 1 and 2, and any other open file stream will have a separate descriptor associated with it.
There's a limit to how many files you can have open at once... | What are file descriptors other than 0, 1 and 2 |
1,320,588,194,000 |
My board boots via U-Boot and AFAIK that bootloader does not support device tree overlays, so I'm probably forced to generate a single, static .dtb will all relevant overlays (and settings??) already applied to it. In principle that would be okay for me, but how to do that?
Is there some command line tool that takes .... |
You don't need to do this.
With this change, overlays are in u-boot!
https://github.com/u-boot/u-boot/commit/e6628ad7b99b285b25147366c68a7b956e362878
Enjoy :)
| how to merge device tree overlays to a single .dtb at build time? |
1,320,588,194,000 |
My board continues to display the message below.
The terminal does not have any input.
What is it with the following message, which I know? (T, g, c, q ...)
What is the cause of this phenomenon?
How can I fix this phenomenon?
INFO: rcu_preempt detected stalls on CPUs/tasks: { 3} (detected by 0, t=3936547 jiffies, g=36... |
You probably have a real time application that is consuming all cpu (some bad implementation) and because of its realtime scheduling priority the system doesn't have enough resources available for other tasks.
I suggests that you remove realtime priority from your applications and check which one is consuming a lot of... | "rcu_preempt detected stalls on CPUs / tasks" message appears to continue |
1,436,241,099,000 |
I have updated the Linux kernel on my system to Linux 3.11-2-amd64 #1 SMP Debian 3.11.10-1 (2013-12-04) x86_64 GNU/Linux. Having done that, the sound no longer works.
Distribution Info(cat /etc/*-release):
PRETTY_NAME="Debian GNU/Linux jessie/sid"
NAME="Debian GNU/Linux"
ID=debian
ANSI_COLOR="1;31"
HOME_URL="http://... |
Well I found the solution :
rm -r /home/user/.pulse*
And change the file /etc/libao.conf
change(old)
default_driver=alsa
quiet
to (new )
default_driver=pulse
quiet
and restart your system.
| After upgrading the kernel, the sound no longer works |
1,436,241,099,000 |
I have a problem booting my Debian Linux server. After a system update, GRUB loads the initrd and the system should ask for the password, but it doesn't. Instead, I get dropped to BusyBox. After trying to mount the encrypted volume manually with cryptsetup luksOpen, I get this error:
device-mapper: table: 254:0: crypt... |
Your kernel lacks support for aes-cbc-essiv:sha256. “Error allocating crypto tfm” refers to the kernel's cryptographic subsystem: some necessary cryptographic data structure couldn't be initialized. Your support for cryptographic algorithms comes in modules, and you have a module for the AES algorithm and a module for... | Booting encrypted root partion fails after system update |
1,436,241,099,000 |
Since linux 2.6.30, filesystems are mounted with "relatime" by default. In this discussion, Ingo Molnar says he has added the CONFIG_DEFAULT_RELATIME kernel option, which:
makes 'norelatime' the default for all mounts without an extra kernel
boot option.
I don't really get it, I wonder if that means that without C... |
Ingo Molnar proposed a patch, but this patch wasn't accepted into the kernel tree. Linus Torvalds made relatime the default setting in 2.6.30, unconditionally, and this is still true in 3.0. If you want relatime to default off in the kernel, you need to apply Ingo Molnar's patch in your copy of the source.
| How to configure CONFIG_DEFAULT_RELATIME to disable relatime |
1,436,241,099,000 |
The description of the bzImage in Wikipedia is really confusing me.
The above picture is from Wikipedia, but the line next to it is:
The bzImage file is in a specific
format: It contains concatenated
bootsect.o + setup.o + misc.o +
piggy.o.
I can't find the others (misc.o and piggy.o) in the image.
I would... |
Till Linux 2.6.22, bzImage contained:
bbootsect (bootsect.o):
bsetup (setup.o)
bvmlinux (head.o, misc.o, piggy.o)
Linux 2.6.23 merged bbootsect and bsetup into one (header.o).
At boot up, the kernel needs to initialize some sequences (see the header file above) which are only necessary to bring the system into a de... | More doubts in bzImage |
1,436,241,099,000 |
I'm trying to mirror a website locally. However, I've been running into a segmentation fault at some consistent point in the download, on a different domain than the site I'm targeting (probably due to --page-requisites).
2018-04-09 04:58:32 (346 KB/s) - './not-website.com/2017/06/28/xyz/index.html' saved [145810]
29... |
Segmentation Fault means the program, in this case, wget, tried to access an invalid memory address and therefore was terminated by the kernel. This typically happen due to a program bug, so while it is quite likely it is being triggered by a specific website or web page (considering you seem to be able to reproduce i... | Wget segfault---how do I know which site is causing this? |
1,436,241,099,000 |
I was trying to change linux process priority using chrt. I changed priority of one process to SCHED_FIFO from SCHED_OTHER. I could see some improvement in the perfomance. I run linux angstrom distribution for my embedded system.
So if I use SCHED_FIFO for one process, how other process will get affected? What are th... |
As explained in sched_setscheduler(2), SCHED_FIFO is RT-priority, meaning that it will preempt any and all SCHED_OTHER (ie. "normal") tasks if it decides it wants to do something.
So, you should be absolutely sure it is well written and will yield control periodically by itself, because if it decides not to (eg. it wa... | SCHED_FIFO and SCHED_OTHER |
1,436,241,099,000 |
I first found this by investigating parameters for earlycon but found that the options for console look almost identical. Both are present below and were taken from this source:
From documentation for console we have:
console= [KNL] Output console device and options.
tty<n> Use the virtual console device <n>... |
I'm sure someone is still doing this, but back in the days before stuff like ILO/DRAC/etc. became cheap and ubiquitous, the best way to get "out of band" access to the console in case of emergencies or an oops was over the serial port. You would mount a Terminal Server in the rack, then run cables to the serial port o... | Kernel parameters "console" and "earlycon" refer to old hardware? |
1,436,241,099,000 |
How do I activate extra verbosity during boot, on Debian? I removed the quiet parameter and tried to add debug but it didn't help.
My problem is that my keyboard takes 2-3 min to activate so it slows my startup tremendously since I need to unlock a partition. I would like to get the message that pops out the moment m... |
There is a list of all possible boot parameters. I've never used it, but try adding ignore_loglevel:
Ignore loglevel setting - this will print /all/ kernel messages to the console. Useful for debugging. We also add it as printk module parameter, so users could change it dynamically, usually by /sys/module/printk/p... | How can I activate extra-verbose mode (debugging mode) during Debian boot? |
1,436,241,099,000 |
I have a Xilinx FPGA PCIe end-point on the PCI Bus.
Linux picks up the device just fine and everything in lspci looks perfect.
My question is about PCI access options from user-space and what would be good/bad.
Option 1: Direct access via /sys/.../resource0
(only one I have managed to make work so far)
I can open and ... |
Option 1 (direct access via /sys/.../resource0)
Good for testing and nothing wrong with it functionally, although can not do anything advanced and no driver layer abstraction. I find this method icky by the way the user program interacts with the sysfs but that might be my personal opinion.
Option 2 (using uio_pci_gen... | Linux Userspace PCI driver options? (uio_pci_generic) |
1,436,241,099,000 |
I'm using an Ubuntu Server (13.04) Minimal installation (with the Xubuntu Metapackage as a desktop environment, if that matters) on x86_64 on my Samsung notebook. I'm currently forced to use the no-longer-maintained version of the proprietary AMD graphics driver (fglrx-legacy) as the open-source "radeon" driver heats ... |
Sorry, I totally forgot this question.
The solution back then was to use the Saucy (Ubuntu 13.10) Kernel, which is based on 3.11, instead of the vanilla/mainline one. Some changes probably broke compatibility, at least with my combination of hardware and software.
| Kernel freezes on loading ramdisk. How to find out what's wrong? |
1,436,241,099,000 |
I write a kernel module which has initialize and end function. I want one more function and want to call it from the user space process at any time i want.
Is it applicable ? If so, how ?
I am working on CentOS 5.2 and custom kernel, patched from linux 2.6.18.
EDIT:
To make clear, I want to write a function into ker... |
Doing a kernel module that can use the /proc filesystem sounds like it might work for you. IBM developerWorks has an article on that topic. I worked through the code a few years ago, and it worked back then. The article is dated 2006, and seems to apply to Linux 2.6 kernels.
The problem I can foresee with using "file... | kernel module function call |
1,436,241,099,000 |
I am working on a project that includes building an old kernel version of linux. This is fine, but I still need to patch the kernel of all previously found security vulnerabilities based on CVEs. I have the CVEs and have extracted the names of the vulnerable files mentioned in them, along with the kernel versions it... |
Do the build, then list the .o files. I think every .c or .S file that takes part in the build is compiled into a .o file with a corresponding name. This won't tell you if a security issue required a fix in a header file that's included in the build.
make vmlinux modules
find -name '*.o' -exec sh -c '
for f; do fo... | How do I know which files will be included in a linux kernel before I build it? |
1,436,241,099,000 |
Is it possible to restart only the userspace? Like shutdown everything up to the kernel and then restart from PID 1?
I would like to snapshot my root btrfs filesystem and quickly boot on that snapsnot.
|
You are probably inspired by macOS launchctl reboot userspace feature; unfortunately systemd lacks this feature (systemd can re-launch itself with systemctl daemon-reexec, but this does not terminate all children), however you can get an even better result than macOS' reboot userspace by using the kexec feature of the... | Reboot only userspace |
1,436,241,099,000 |
I need to upgrade my centos OS to kernel-3.10.0-862 to address the security issue. When I run yum check-update|grep kernel Gives only 693.21
kernel.x86_64 3.10.0-693.21.1.el7 updates
I do see the updated kernel here :
http://mirror.centos.org/centos/7/updates/x86_64/Packages/
What is ... |
Within /etc/yum.repos.d, you should see a repo called CentOS-CR.repo which will be disabled. Set enabled to 1 and then yum list available | grep kernel and you'll see the kernel packages for 3.10.0-862.
After that, you can yum update or yum install kernel* to get the new kernel packages.
I just ran yum update on my Ce... | Centos 7 updated kernel to kernel-3.10.0-862 using YUM |
1,436,241,099,000 |
I have an Atmel SAM9X system running Angstrom. I am trying to make a recovery partition so when a user holds a button during boot up the recovery partition boots up.
I have modified the bootstrap so when a button is held on boot up, an alternate linux kernel is loaded. What I want is the alternate kernel to load linu... |
The kernel contains a default root partition setting, determined at compile time (you can change it in the binary image with the rdev command). You can pass an argument on the kernel command line to override this default at boot time, e.g. root=/dev/mmcblk9p42 to boot from MMC device 9 partition 42 instead of the defa... | Making a recovery partition in embedded Linux |
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