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of machines: ifconfig eth0 netmask 255.255.255.128 Try it too. That restricts the card to at most the address space between .0 and .127. Now you can set your second card up in the other half of the local address space. Make sure that nobody already has the address. For symmetry I set it at 228=128+100 here. Any address... |
is not in the other card's mask, and even then, well, maybe. Avoid special addresses like .0, .1, .128 etc. unless you really know what you are doing. ifconfig eth1 192.168.2.228 netmask 255.255.255.128 metric 1 That restricts the second card to addresses between .128 and .255. This is where I have to announce the cave... |
packets which are not routed. No routes, no firewall. At least this appears to be true in the 2.0.30 and more recent kernels. The firewalling filters are closely involved with the ip-forwarding code. That does not mean that you cannot bridge. You can bridge between two cards and firewall them from a third. You can have... |
against an outside IP such as a nearby router, provided that the router is routed by you to exactly one of the cards. In other words, since I will be doing firewalling, so I want to precisely control the physical destination of some packets. I have the small net of machines attached to a hub hanging off eth0, so I conf... |
route add -net 192.168.2.128 netmask 255.255.255.128 dev eth0 The 128 would be 0 if I had a full class C network there. I don't, by definition, since I just halved the address space. The "dev eth0" is not necessary here because the cards address falls within the mask, but it may be necessary for you. One might need mor... |
this subnet (127 machines on one segment, oh yeah) but those cards would be being bridged under the same netmask so that they appear as one to the routing code. On the other card I have a line going straight through to a big router that I trust. client 129 __ | __ client 1 \ .0 .128 | / net 1 client 2 |
--- Hub - eth0 - Kernel - eth1 - Hub - Router --- net 2 client 3 __/ .100 .228 .2 | \__ net 3 | client 254 I attach the address of the router to that card as a fixed ("static") route because it would otherwise fall within the first cards netmask and the kernel would be thinking wrongly about how to send |
packets to the big router. I will want to firewall these packets and that is another reason fow wanting to route them specifically. route add 192.168.2.2 dev eth1 I don't need it, since I don't have any more machines in that half of the address space, but I declare a net also on the second card. Separating my interface... |
will allow me to do very tight firewalling eventually , but you can get away with far less routing than this. route add -net 192.168.2.128 netmask 255.255.255.128 dev eth1 I also need to send all non-local packets out to the world so I tell the kernel to send them to the big router route add default gw 192.168.2.2 So m... |
but we are bridging so we also have to listen on both (?) cards for packets that are not aimed at us. The following should go into the network configuration file. ifconfig promisc eth0 ifconfig promisc eth1 The man page says allmulti=promisc, but it didn't work for me. One thing that I noticed was that I had to put at ... |
into a mode where it would respond to the big router's questions about which machines I was hiding in my local net. ifconfig arp eth1 For good measure I did this to the other card too. ifconfig arp eth0. Put bridging enabling on and into your configuration file: You should have been trying this out in real time all alo... |
configure will bring up some numbers. You can experiment with turning on and off the ports one at a time brcfg -port 0 -disable/-enable brcfg -port 1 -disable/-enable You get status reports anytime by just running without any parameters. You will see that the bridge listens,learns, and then does forwarding. (I don't un... |
cards, but never mind .. Chris' howto say that is OK) If you are still up and running as things are, try out your configuration script for real by taking down both cards and then executing it: ifconfig eth0 down ifconfig eth1 down /etc/rc.d/rc.inet1 With any luck the various subsystems (nfs, ypbind, etc.) won't notice.... |
the keyboard! If you want to be more careful than this, you should take down as many daemons as possible beforehand, and unmount nfs directories. The worst that can happen is that you have to reboot in single-user mode (the "single" parameter to lilo or loadlin), and take out your changes before rebooting with things t... |
there is different traffic on each interface: tcpdump -i eth0 (in one window) tcpdump -i eth1 (in another window) You should get used to using tcpdump to look for things that should not be happening or that are happening and should not. For instance look for packets that have gone through the bridge to the second card ... |
looking for packets from the machine with address .22: tcpdump -i eth1 -e host 192.168.2.22 Then send a ping from the .22 host to the router. You should see the packet reported by tcpdump. At this stage you should have a bridge ready that also has two network addreses. Test that you can ping them from outside and insid... |
you can telnet and ftp around between inside and outside too. You should read the Firewall-HOWTO. That will tell you where to get ipfwadm if you don't already have it. There are other tools you can get but I made no progress until I tried ipfwadm. It is nice and low level! You can see exactly what it is doing. You have... |
and masquerading into the kernel so you will want to check that the firewall is in its default (accepting) state with ipfwadm -I -l ipfwadm -O -l ipfwadm -F -l That is respectively, "display the rules affecting the .." incoming or outgoing or forwarding (masquerading) ".. sides of the firewall". The "-l" means "list". ... |
You should see that there are no rules defined and that the default is to accept every packet. You can get back to this working state anytime with ipfwadm -I -f ipfwadm -O -f ipfwadm -F -f The "-f" means "flush". You may need to use that. I want to cut the world off from my internal net and do nothing else, so I |
format to is rather long-winded. Ipfwadm is intelligent about network names and some common abbreviations. Check the man pages. It is possibly more convenient to put some or all of these rules on the outgoing half of the firewall by using "-O" instead of "-I", but I'll state the rules here all formulated for the incomi... |
place some rules that serve as exceptions to this general denial of external services to internal clients. I want to treat the firewall machines address on the internal net specially. I will stop people logging in to the firewall machine unless they have special permission, but once they are there they should be allowe... |
mean that you can just about make first contact, but the clients cannot send you any prompts. You should be able to get all the way in if you use the firewall machine as a staging post. Try rlogin and ping too, with tcpdump running on one card or the other. You should be able to make sense of what you see. I went |
on to relax the rules protocol by protocol. I want to allow pings from the outside to the inside to get an echo back, for instance, so I inserted the rule: ipfwadm -I -i accept -P icmp -S 192.168.2.0/255.255.255.128 \ -D 0.0.0.0/0.0.0.0 -P icmp" works the protocol-specific magic. Until I get hold of an ftp proxy I am a... |
port-specific relaxations. This targets ports 20 21 and 115 on outside machines. ipfwadm -I -i accept -P tcp -S 192.168.2.0/255.255.255.128 \ -D 0.0.0.0/0.0.0.0 20 21 115 I could not make sendmail between the local clients work without a nameserver. Rather than set up a nameserver right then on the firewall, I just lif... |
nearest existing nameserver and put its address in the clients /etc/resolv.conf nameserver 123.456.789.31" on a separate line). ipfwadm -I -i accept -P tcp -S 192.168.2.0/255.255.255.128 \ -D 123.456.789.31/255.255.255.255 54 You can find which port number and protocol a service requires with tcpdump. Trigger the servi... |
it on the input and output ports of the firewall with tcpdump: tcpdump -i eth1 -e host client04 for example. The /etc/services file is another important source of clues. To let telnet and ftp IN to the firewall from outside, you have to allow the local clients to call OUT on a specific port. I understand why this is ne... |
the server that establishes the data stream in the end - but I am not sure why telnet also needs this. ipfwadm -I -i accept -P tcp -S 192.168.2.0/255.255.255.128 ftp telnet \ -D 0.0.0.0/0.0.0.0 There is a particular problem with some daemons that look up the hostname of the firewalling machine in order to decide what i... |
I had trouble with. It insists on broadcasting information that says it is outside the firewall (on the second card). That means the clients inside can't contact it. Rather than start IP aliasing or change the daemon code, I mapped the name to the inside card address on the clients in their /etc/hosts. You want to test... |
ping from the outside. From the inside you should be able to ping out. You should also be able to telnet to the firewall machine from the inside and the latter should be able to do anything. That is it. At this point you probably want to learn about rpc/Yellow Pages and the interaction with the password file. The firew... |
User management is a very basic administrative task on any operating system. Performing that task on Linux is just as simple as on any other OS. Experienced users already know |
how to do this, but if you are a new convert to Linux, and are using Zenwalk 6.2, the latest edition of Zenwalk, this tutorial provides a step-by-step guide on |
how to add a user on a running system. Unless you have granted user management rights to a regular user, adding a user on Zenwalk requires root privileges (Zenwalk uses |
the root account for access to performing admin tasks on the system). You can access the user management application from the Control Panel, itself accessible from Zenwalk menu > Settings |
> Control Panel. On the control panel, click on the User Profiles icon On the User Management screen, select Create user and click OK. Type in the username. The username |
is the name that the user will use to log into the system. By default, the user belongs to the users group. No need to change anything here. By default, |
the user’s home directory is /home/< username >. Again, no need to change anything here. Aside from the users default group, the user also belong to certain system groups. Membership |
in these additional groups allows the user to perform certain tasks on the system. Unless you know what you are doing, don’t change anything here. Bash, Bourne Again Shell, is |
the default shell interpreter on Linux. And the path to bash is usually /bin/bash. OK. Sometimes, you want to create a temporary account for a guest, or you are very |
security conscious and want to implement password aging. In such cases, you can set the password to expire. Select the desired password expiration date and click OK, or click on |
by Dave Phillips OpenAL, the Open Audio Library, is an initiative from Creative Labs and Loki Entertainment designed to provide a cross-platform open source solution for programming 2D and 3D audio. It is licensed under the GNU Lesser General Public License (LGPL), with current implementations supporting Windows, the M... |
applications between supported platforms, particularly games and other multimedia applications using OpenGL for 3D graphics. As its name implies, OpenAL is analogous in many ways to SGI's OpenGL, a widely implemented standard for specifying high-quality 3D graphics (see Chris Halsall's article for more information rega... |
considerations for the visual effects possible from OpenGL, particularly with regard to movement in three dimensions and proximity-dependent texture variance. Because the OpenAL API is so similar to OpenGL, programmers employing OpenGL for graphics can more easily bind sonic activity to visuals, leading to exciting pos... |
simply place their sounds into a scene and let OpenAL render the changes of the sounds relative to the positional changes of the listener. The programming interface is hardware-independent. It can be deployed on virtually any soundcard usable on the supported platforms, though of course its potential will be most fully... |
interface that provides a communication protocol with the sound card driver. For Linux users it should make no difference whether the card driver comes from the kernel sources, ALSA, or OSS/Linux. The OpenAL library is designed to act in coordination with the low-level routines of the driver. At this time the API and l... |
future revisions will address CD audio and hardware MIDI synthesis. OpenAL also follows recommendations put forth by the Interactive Audio Special Interest Group (IASIG). The current API has been written to accommodate at least the following IASIG Level 1 guidelines: - Distance-based attenuation -- the strengthening or... |
the location of a sound is calculated relative to the listener, not merely shifting between speakers. - Doppler effects -- the perceived rise and fall of a sound's pitch as a source approaches and leaves the listener. - Sound radiation -- control of a sound's dispersion through the acoustic field. OpenAL Resources On-l... |
Bernd Kreimeier, Fotis Hadginikos, and Derrick Story for their vast assistance. This series of articles could not have been written without their help. The IASIG Level 2 guidelines specify a set of environment parameters for reverberation. Work has already begun to incorporate those parameters into the OpenAL API. The ... |
SGML format. You will need the DocBook tools to compile the API documentation into readable HTML. The reference documentation is also available on-line here. I should emphasize that the documentation is directed only to developers at this time. As an open source project with corporate blessings, OpenAL seems assured of... |
cross-platform support for 3D audio in games and other multimedia applications, making it of great interest to developers and end-users alike. Even while the 1.0 specification is being ratified, some developers are already employing OpenAL's services. OpenAL is not without its contenders, but those solutions are propri... |
audio) services, and with hardware acceleration, OpenAL could revolutionize computer audio in the same way as OpenGL revolutionized computer graphics, an exciting prospect indeed. As a final reminder, please note that OpenAL is a community effort, and community involvement is encouraged. See the OpenAL Web site for com... |
look at the internals of the API, but first we'll discuss 3D audio and then see what real-world applications have already employed the OpenAL specification. Discuss this article in the O'Reilly Network Linux Forum. Return to the Linux DevCenter. |
Having arrived back in India to take command of Fort St. David, south of Madras, in June 1756, on 16 October 1756 Clive led a British army force from in Madras to retake Calcutta from Siraj-ud-Daula. He recaptured Calcutta on 2 January 1757 and forced Siraj-ud-Daula to pay compensation and permit British fortification ... |
Races start with heats, the number of which depends on the number of swimmers in the event. Swimmers are seeded in advance and these seedings are used to determine the heat each swimmer starts in – the top seeds will be placed in different heats. Seedings are also used to |
determine the lane each athlete will swim in – the higher the seeding the closer to the centre lanes of the pool. The top eight swimmers from the heats progress to the final. As in the heats, the swimmers’ seedings are used to decide which lane they are allocated. Swimming |
How To Start Rock Climbing When thinking about how to start rock climbing, many people assume that you need a physique of Sylvester Stallone in "Cliffhanger". But if you take the right steps in preparing yourself for this mentally and physically stimulating work out, you will surprise yourself with how good you can be.... |
mentally. However, the end reward makes it all very worth it. To start rock climbing you will need the following items: - climbing shoes - climbing rope - a harness - a belay device - chalk (optional; used by some climbers to help with their grip) The number one lesson in beginning your adventure is that you can never ... |
professional lesson in belaying, harness and rope safety, and the terminologies of rock climbing. If you go to any indoor rock climbing facility they should have the staff to provide you with such a lesson, they should also have equipment that you can rent. Be sure to wear comfortable but tighter clothing that you can ... |
comfortable at an indoor facility before you should attempt to rock climb in the outdoors. Rocks are much less forgiving on beginners mistakes and so are the elements of nature. - Learn how to do "top rope" climbing. This form of climbing is the safest form. The rope that is connected to you (the climber) goes up and t... |
top of the wall and back down to your belayer (the person on the ground who holds the rope). Be sure to utilize the person you have belaying. They can instruct you on where to look for good holds and can be a great source of encouragement if you start to struggle. With this form of climbing it is very difficult for you... |
fall far and you can take breaks easier. Rock climbing, even in the elementary stages, is a very intense cardio work out as well as a mental challenge. But the more often you participate in rock climbing, the better you will be physically and at finding good holds for your hands and feet. - Start to challenge yourself ... |
the basics that you've learned from your lesson, its time to make it real. The wall at the indoor facility will have these routes marked off by coloured tape. Trying to stay on these routes will give you a better concept of climbing outdoors as there aren't options or cheats on the side of a rock face. The routes are a... |
scale. Try to master a few of the easiest routes and then push yourself to the next level of the scale. The higher the number the higher the difficulty of the route. - Consider taking a course on "lead" climbing. Once you feel comfortable at the indoor facility on top rope, try this type of climbing. It requires you to... |
caribbeaners as you, is a slightly more intense and much more skillful form of climbing. You need to absolutely feel secure in your abilities and the person you have handling your belay in order to participate in lead climbing. - Consider going to an outdoor rock face. After mastering lead climbing, try this. Be sure t... |
know some hints before trying to go on your own. Red River Gorge in Kentucky is a great location for a plethora of different types of routes. As with any new skill, practice makes perfect. You shouldn't expect to be Mr. Stallone within your first few attempts. Just continue trying and pushing yourself psychically and m... |
LOS ANGELES — Researchers have some new advice for high school students who want to improve their grades: Become friends with academically oriented classmates. It may sound obvious, but researchers went to considerable effort to prove it. They surveyed all members of the junior class at Maine-Endwell High School in End... |
"best friend," a "friend," an "acquaintance" or someone they didn't know. They got responses from 92 percent of students and used them to reconstruct the social networks among 158 11th-graders as of Jan. 11, 2011. The research team also obtained the grade point averages for all 158 students in January 2011 and January ... |
time. For the analysis, those GPAs were converted into class rankings. Then they compared the rankings of each student to those of their best friends, friends and acquaintances. Sure enough, the researchers found a linear relationship between a student's grades and the academic environment of their social network. If a... |
her social network, it tended to fall over the course of the year. Conversely, if a student ranked below the rest of her group, her class ranking tended to rise. The most significant influence appeared to be the grades of those labeled as "friends." To explain this, the researchers hypothesized that the grades of "best... |
were probably very similar to start with. But the gaps between students and their "friends" were bigger, so there was more opportunity for influence. The findings were published recently in the journal PLOS ONE. The results are in line with other studies showing that happiness, obesity and other traits can spread throu... |
Send SCSI READ LONG command to DEVICE. The read buffer is output in hex and ASCII to stdout or placed in a file. Note that the data returned includes the |
logical block data (typically 512 bytes for a disk) plus ECC information (whose format is proprietary) plus optionally other proprietary Arguments to long options are mandatory for short options as |
well. uses a SCSI READ LONG(16) command. The default action is to use a SCSI READ LONG(10) command. The READ LONG(10) command has a 32 bit field for the lba |
while READ LONG(16) has a 64 bit field. sets the 'CORRCT' bit in the SCSI READ LONG command. When set the data is corrected by the ECC before being transferred |
back to this utility. The default is to leave the 'CORRCT' bit clear in which case the data is output the usage message then exit. where LBA is the logical |
block address of the sector to read. Assumed to be in decimal unless prefixed with '0x' (or has a trailing 'h'). Defaults to lba 0. If the lba is larger |
than can fit in 32 bits then the --16 option should be used. instead of outputting ASCII hex to stdout, send it in binary to the file called OF. If |
'-' is given for OF then the (binary) output is sent to stdout. Note that all informative and error output is sent to stderr. sets the 'PBLOCK' bit in the |
SCSI READ LONG command. When set the physical block (plus ECC data) containing the requested logical block address is read. The default is to leave the 'PBLOCK' bit clear in |
which case the logical block (plus any ECC data) is read. opens the DEVICE read-only rather than read-write which is the default. The Linux sg driver needs read-write access for |
the SCSI READ LONG command but other access methods may require read-only increase the level of verbosity, (i.e. debug output). print the version string and then exit. where BTL is |
the byte transfer length (default to 520). If the given value (or the default) does not match the "long" block size of the device, the appropriate BTL is deduced from |
the error response and printed (to stderr). The idea is that the user will retry this utility with the correct transfer length. If a defective block is found and its |
contents, if any, has been retrieved then "sg_reassign" could be used to map out the defective block. Associated with such an action the number of elements in the "grown" defect |
list could be monitored (with "sg_reassign --grown") as the disk could be nearing the end of its useful lifetime. Various numeric arguments (e.g. LBA) may include multiplicative suffixes or be |
given in hexadecimal. See the "NUMERIC ARGUMENTS" section in the sg3_utils(8) man page. As a data point, Fujitsu uses a 54 byte ECC (per block) which is capable of correcting |
up to a single burst error or 216 bits "on the fly". [Information obtained from MAV20xxrc product manual.] The exit status of sg_read_long is 0 when it is successful. Otherwise |
Description of How We Got the Bible by Neil Lightfoot How We Got the Bible provides factual, accessible answers to questions such as How and when did the books of the Bible originate? In what sense are these books different from other books? How have these books been preserved and transmitted to us? Why do we have so m... |
A popular guide for Bible students, it has sold more than 1 million copies during its forty years in print. This trade paper edition of the well-loved classic offers readers an even more affordable way to learn about the development of the most important book in history. |
Education That is Multicultural and Achievement (ETMA) The Maryland State Department of Education implements a State Regulation (COMAR 13A.04.05), expanded in 1995 and revised in 2005, that requires all local school systems to infuse Education That Is Multicultural into instruction, curriculum, staff development, instr... |
publications,and assessments. Education That Is Multicultural is defined as "a continuous, integrated, multicisciplinary process for educating all students about diversity and commonality. Diversity factors include, but a not limited to race, ethnicity, region , religion, gender, language, socioeconomic status, age, an... |
The Patrick administration has been working to enhance its long-term financial planning based on best practices prescribed by the Government Finance Officers Association (GFOA). Best practices include the use of a sound conceptual approach, ensuring that near-term decisions measure long-term |
impacts, and developing a solution framework that is aligned with policy goals. The Commonwealth has implemented a conceptual approach of “structural balance“ that is designed to delineate among different causes of fiscal imbalance. The application of this approach identifies three |
critical challenges facing the Commonwealth: a remaining structural deficit due to the significant reduction in tax revenue since the recession, cost inflation on safety net and health care programs, and the need to improve policy measures to address economic volatility. |
Each of these challenges is a central feature of our FY12 budget proposal as further described in the conclusion to this section. Structural Balance Approach and Analysis The goal of structural balance is to base spending on policy priorities and |
a predictable level of sustainable revenue. Our supporting analysis includes a five-year forecast for revenue and spending based on historical trends as well as the outlook for the state economy. The forecast includes a projection of tax revenue, based on |
input from local economists, that also provides the basis to develop an estimated long-term trend-line for tax revenue. The forecast indicates that the state economy will be below trend during a four year recovery period beginning in fiscal year 2012 |
before reaching a “steady-state” level of long-term tax revenue growth of approximately 5% in 2016. The imputed trend-line was developed using the tax revenue figures from 2016 and discounting revenue back by the estimated 5% annually. A similar approach was |
taken to develop a pre-recession revenue trend-line and select results of this analysis are highlighted in the exhibit below. (note: the time horizon in the exhibit has been truncated in order to emphasize the key findings discussed below). The results |
of this analysis provide three useful insights into our near-term fiscal challenges. First, tax revenue in FY07 (i.e. pre-recession) was approximately $2 billion greater than the then current trend-line. Second, the impact of the recession on this trend-line after FY09 |
was a significant downward shift of an additional $2 billion. Finally, the outlook for the economy suggests that recovery in tax revenue will be only modest: approximately $500 million based on the difference between the trend and forecast for tax |
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