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Editing of new "Linux-Networking" guide. This copy is not to be distributed. Its just a draft to give people an idea as to the format of the new document and a backup just in case my laptop dies. 

Binh.
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binh 2004-11-17 12:04:21 +00:00
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1662
LDP/guide/docbook/Linux-Networking/Glossary.xml
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LDP/guide/docbook/Linux-Networking/Multicast.xml
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This feature is desirable in some cases, but not in others. So the
sending process can turn it on and off at wish.
2.3.3. Interface selection.
Hosts attached to more than one network should provide a way for
@ -282,8 +280,6 @@
the transmissions. If not specified, the kernel chooses a default one
based on system administrator's configuration.
2.4. Receiving Multicast Datagrams.
2.4.1. Joining a Multicast Group.
@ -326,8 +322,6 @@
address and port to demultiplex the packets and decide which socket(s)
deliver them to.
2.4.2. Leaving a Multicast Group.
When a process is no longer interested in a multicast group, it
@ -1430,8 +1424,6 @@
o "Administratively Scoped IP Multicast". draft-ietf-mboned-admin-ip-
space-03.txt. D. Meyer. June 10, 1997.
10.3. Web pages.

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LDP/guide/docbook/Linux-Networking/NTP.xml
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LDP/guide/docbook/Linux-Networking/Networking-Management.xml
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<title>Network-Management</title>
<para>
9.1. Network management applications
There is an impressive number of tools focused on network management
and remote administration. Some interesting remote administration
projects are linuxconf and webmin:
· Webmin <http://www.webmin.com/webmin/>
· Linuxconf <http://www.solucorp.qc.ca/linuxconf/>
Other tools include network traffic analysis tools, network security
tools, monitoring tools, configuration tools, etc. An archive of many
of these tools may be found at Metalab
<http://www.metalab.unc.edu/pub/Linux/system/network/>
9.2. SNMP
The Simple Network Management Protocol is a protocol for Internet
network management services. It allows for remote monitoring and
configuration of routers, bridges, network cards, switches, etc...
There is a large amount of libraries, clients, daemons and SNMP based
monitoring programs available for Linux. A good page dealing with SNMP
and Linux software may be found at : http://linas.org/linux/NMS.html
10. Enterprise Linux Networking
In certain situations it is necessary for the networking
infrastructure to have proper mechanisms to guarantee network
availability nearly 100% of the time. Some related techniques are
described in the following sections. Most of the following material
can be found at the excellent Linas website:
http://linas.org/linux/index.html and in the Linux High-Availability
HOWTO <http://metalab.unc.edu/pub/Linux/ALPHA/linux-ha/High-
Availability-HOWTO.html>
10.1. High Availability
Redundancy is used to prevent the overall IT system from having single
points of failure. A server with only one network card or a single
SCSI disk has two single points of failure. The objective is to mask
unplanned outages from users in a manner that lets users continue to
work quickly. High availability software is a set of scripts and tools
that automatically monitor and detect failures, taking the appropriate
steps to restore normal operation and to notifying system
administrators.
10.2. RAID
RAID, short for Redundant Array of Inexpensive Disks, is a method
whereby information is spread across several disks, using techniques
such as disk striping (RAID Level 0) and disk mirroring (RAID level 1)
to achieve redundancy, lower latency and/or higher bandwidth for
reading and/or writing, and recoverability from hard-disk crashes.
Over six different types of RAID configurations have been defined.
There are three types of RAID solution options available to Linux
users: software RAID, outboard DASD boxes, and RAID disk controllers.
· Software RAID: Pure software RAID implements the various RAID
levels in the kernel disk (block device) code.
· Outboard DASD Solutions: DASD (Direct Access Storage Device) are
separate boxes that come with their own power supply, provide a
cabinet/chassis for holding the hard drives, and appear to Linux as
just another SCSI device. In many ways, these offer the most robust
RAID solution.
· RAID Disk Controllers: Disk Controllers are adapter cards that plug
into the ISA/EISA/PCI bus. Just like regular disk controller cards,
a cable attaches them to the disk drives. Unlike regular disk
controllers, the RAID controllers will implement RAID on the card
itself, performing all necessary operations to provide various RAID
levels.
Related HOWTOs:
· http://metalab.unc.edu/mdw/HOWTO/mini/DPT-Hardware-RAID.html
· http://metalab.unc.edu/mdw/HOWTO/Root-RAID-HOWTO.html
· http://metalab.unc.edu/mdw/HOWTO/Software-RAID-HOWTO.html
RAID at linas.org:
· http://linas.org/linux/raid.html
10.3. Redundant networking
IP Address Takeover (IPAT). When a network adapter card fails, its IP
address should be taken by a working network card in the same node or
in another node. MAC Address Takeover: when an IP takeover occurs, it
should be made sure that all the nodes in the network update their ARP
caches (the mapping between IP and MAC addresses).
See the High-Availability HOWTO for more details:
http://metalab.unc.edu/pub/Linux/ALPHA/linux-ha/High-Availability-
HOWTO.html
There is an impressive number of tools focused on network management
and remote administration under Linux. Some interesting remote administration
projects are linuxconf and webmin:
</para>
</sect1>
<para>
· Webmin <http://www.webmin.com/webmin/>
· Linuxconf <http://www.solucorp.qc.ca/linuxconf/>
</para>
<para>
Other tools include network traffic analysis tools, network security
tools, monitoring tools, configuration tools, etc. An archive of many
of these tools may be found at Metalab
<http://www.metalab.unc.edu/pub/Linux/system/network/>
</para>
9.2. SNMP
<para>
The Simple Network Management Protocol is a protocol for Internet
network management services. It allows for remote monitoring and
configuration of routers, bridges, network cards, switches, etc...
There is a large amount of libraries, clients, daemons and SNMP based
monitoring programs available for Linux. A good page dealing with SNMP
and Linux software may be found at : http://linas.org/linux/NMS.html
</para>
10. Enterprise Linux Networking
<para>
In certain situations it is necessary for the networking
infrastructure to have proper mechanisms to guarantee network
availability nearly 100% of the time. Some related techniques are
described in the following sections. Most of the following material
can be found at the excellent Linas website:
http://linas.org/linux/index.html and in the Linux High-Availability
HOWTO <http://metalab.unc.edu/pub/Linux/ALPHA/linux-ha/High-
Availability-HOWTO.html>
</para>
10.1. High Availability
<para>
Redundancy is used to prevent the overall IT system from having single
points of failure. A server with only one network card or a single
SCSI disk has two single points of failure. The objective is to mask
unplanned outages from users in a manner that lets users continue to
work quickly. High availability software is a set of scripts and tools
that automatically monitor and detect failures, taking the appropriate
steps to restore normal operation and to notifying system
administrators.
</para>
</sect1>

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LDP/guide/docbook/Linux-Networking/Quota.xml
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<title>Quota</title>
<para>
This section describes how to enable file system quota on a Linux
host, assigning quota for users and groups, as well as the usage of
miscellaneous quota commands. It is intended for users running kernel
2.x (recently tested on kernel 2.4.21).
1. What is quota?
1.1. What is quota for?
Quota allows you to specify limits on two aspects of disk storage: the
number of inodes a user or a group of users may possess; and the
number of disk blocks that may be allocated to a user or a group of
users.
The idea behind quota is that users are forced to stay under their
disk consumption limit, taking away their ability to consume unlimited
disk space on a system. Quota is handled on a per user, per file
system basis. If there is more than one file system which a user is
expected to create files, then quota must be set for each file system
separately. Various tools are available for you to administer and
automate quota policies on your system.
1.2. Current Status of Quota on Linux
Currently, there are some major changes in the way quota works. There
are two different setups. The tools works the same, but there's a
difference in used files. This document describes the setup and
operation of the _new_ quota setup. As the new setup of quota is not
in the regular kernel source, this setup needs some patching. We will
describe this patching and installation of the linuxquota package. If
you already have the quota software installed on your system, you may
or may not have to install this patch and package. You can email me if
you have any questions about this. I'll try to include a overview of
Linux distro's and it's implications in a later version of this
document.
2. Requirements for quota
2.1. Kernel
The 2.x kernel source is available from http://www.kernel.org
<http://www.kernel.org/> Please use an available mirror close to your
location to save bandwidth. If you have a recent version of tar, you
can download the .bz2 compressed file.
Untar the kernel:
______________________________________________________________________
cd /usr/src
tar jxvf /path/to/linux-2.4.21-tar.bz2 - for bzip2 kernel -
tar zxvf /path/to/linux-2.4.21-tar.gz - for gzip kernel -
ln -s /usr/src/linux-2.4.21 /usr/src/linux
______________________________________________________________________
2.2. Quota software
Depending on the Linux distribution you have, you may, or may not have
the quota softwares installed on your system. The most recent version
of quota is available through SourceForge and is in active
development. You can reach the homepage of the quota-development at
http://www.sourceforge.net/projects/linuxquota
<http://www.sourceforge.net/project/linuxquota>.
3. Quota setup: installation and configuration
3.1. Patch the kernel
Download the patch for your kernel at:
ftp::/atrey.karlin.mff.cuni.cz/pub/local/jack/quota/
<ftp://atrey.karlin.mff.cuni.cz/pub/local/jack/quota/>.
Choose your kernel version and download the patch(es). Patch your
kernel with the 'patch' command. If there is more than 1 patch for
your kernel version, be sure to apply the patches in the correct
order.
You can use this script ( I assume the downloaded patches are in
/tmp/quota/ and the kernel has been untarred to /usr/src/linux) :
______________________________________________________________________
#!/bin/sh
gunzip /tmp/quota/*.gz
cd /usr/src/linux
COUNT=`ls -1 /tmp/quota/*.diff | wc -l`
for I in `seq 1 $COUNT`
do
patch -p1 < /tmp/quota/quota-2.4.21-$I-*.diff
done
______________________________________________________________________
3.2. Reconfigure your kernel
Reconfigure your kernel and add quota support.
Via `make menuconfig` or `make xconfig` you can find the option to
support quota under the Filesystems-menu. You can specify extra
options if you need them, like 32-bit UID support.
Save the configuration and compile the kernel. Make sure the new
kernel will be used when rebooting the system.
3.3. Compile and install the quota softwares
To be able to use all the features of the new quota system, you'll
probably need to download the new quota-package. Download the new
quota software via the URL provided above.
When downloaded do:
______________________________________________________________________
$ gzip -dc <downloaded file> | tar xvf
$ cd quota-tools (or whatever directory the software is put in)
$ ./configure
$ make
$ su
# make install
______________________________________________________________________
3.4. time Modify your system init script to check quota and turn
quota on at boot
Here's an example:
______________________________________________________________________
# Check quota and then turn quota on.
if [ -x /usr/sbin/quotacheck ]
then
echo "Checking quotas. This may take some time."
/usr/sbin/quotacheck -avug
echo " Done."
fi
if [ -x /usr/sbin/quotaon ]
then
echo "Turning on quota."
/usr/sbin/quotaon -avug
fi
______________________________________________________________________
The golden rule is that always turn quota on after your file systems
in /etc/fstab have been mounted, otherwise quota will fail to work. I
recommend turning quota on right after the part where file systems are
mounted in your system init script.
3.5. Modify /etc/fstab
Partitions that you have not yet enabled quota normally look something
like:
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults 1 1
______________________________________________________________________
To enable user quota support on a file system, add "usrquota" to the
fourth field containing the word "defaults" (man fstab for details).
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota 1 1
______________________________________________________________________
Replace "usrquota" with "grpquota", should you need group quota
support on a file system.
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,grpquota 1 1
______________________________________________________________________
Need both user quota and group quota support on a file system?
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota,grpquota 1 1
______________________________________________________________________
3.6. Activate the quota system
To activate the quota software you have to reboot the system for the
changes you have made to take effect. The new kernel with quota
support will be loaded and the startup scripts you've just created
will be executed. At first run, quotacheck will generate the
appropiate files to maintain the quota databases.
3.7. Add quotacheck to crontab
Although quota should work with periodical checks, it sometimes helps
to run quotacheck periodically, e.g. weekly. Add the following line to
your root's crontab:
______________________________________________________________________
0 3 * * 0 /sbin/quotacheck -avug
______________________________________________________________________
4. Quota setup: tools
This operation is performed with the edquota command (`man edquota`
for details).
4.1. Assigning quota for a particular user
Here's an example. I have a user with the login id bob on my system.
The command "edquota -u bob" takes me into vi (or editor specified in
my $EDITOR environment variable) to edit quota for user bob on each
partition that has quota enabled:
______________________________________________________________________
Quotas for user bob:
/dev/hda3: blocks in use: 2594, limits (soft = 5000, hard = 6500)
inodes in use: 356, limits (soft = 1000, hard = 1500)
______________________________________________________________________
"blocks in use" is the total number of blocks (in kilobytes) a user
has consumed on a partition.
"inodes in use" is the total number of inodes a user has consumed on a
partition.
4.2. Assigning quota for a particular group
Now I have a group games on my system. "edquota -g games" takes me
into the vi editor again to edit quota for the group games:
______________________________________________________________________
Quotas for group games:
/dev/hda4: blocks in use: 5799, limits (soft = 8000, hard = 10000)
inodes in use: 1454, limits (soft = 3000, hard = 4000)
______________________________________________________________________
4.3. Assigning quota for a bunch of users with the same value
To rapidly set quotas for, say 100 users, on my system to the same
value as my user bob, I would first edit bob's quota information by
hand, then execute:
______________________________________________________________________
edquota -p bob `awk -F: '$3 > 499 {print $1}' /etc/passwd`
______________________________________________________________________
assuming that you are using csh, and that you assign your user UID's
starting with 500.
In addition to edquota, there are 3 terms which you should familiarize
yourself with: Soft Limit, Hard Limit, and Grace Period.
4.4. Soft Limit
_Soft limit_ indicates the maximum amount of disk usage a quota user
has on a partition. When combined with grace period, it acts as the
border line, which a quota user is issued warnings about his impending
quota violation when passed.
4.5. Hard Limit
Hard limit works only when grace period is set. It specifies the
absolute limit on the disk usage, which a quota user can't go beyond
his hard limit.
4.6. Grace Period
Executed with the command "edquota -t", grace period is a time limit
before the soft limit is enforced for a file system with quota
enabled. Time units of sec(onds), min(utes), hour(s), day(s), week(s),
and month(s) can be used. This is what you'll see with the command
"edquota -t":
______________________________________________________________________
Time units may be: days, hours, minutes, or seconds
Grace period before enforcing soft limits for users:
/dev/hda2: block grace period: 0 days, file grace period: 0 days
______________________________________________________________________
Change the 0 days part to any length of time you feel reasonable. I
personally would choose 7 days (or 1 week).
5. Miscellaneous Quota Commands
5.1. Quotacheck
Quotacheck is used to scan a file system for disk usages, and updates
the quota record file "aquota.user" to the most recent state. I
recommend running quotacheck at system bootup, and via cronjob
periodically (say, every week?).
5.2. Repquota
Repquota produces a summarized quota information for a file system.
Here is a sample output repquota gives:
______________________________________________________________________
# repquota -a
Block limits File limits
User used soft hard grace used soft hard grace
root -- 175419 0 0 14679 0 0
bin -- 18000 0 0 735 0 0
uucp -- 729 0 0 23 0 0
man -- 57 0 0 10 0 0
user1 -- 13046 15360 19200 806 1500 2250
user2 -- 2838 5120 6400 377 1000 1500
______________________________________________________________________
5.3. Quotaon and Quotaoff
Quotaon is used to turn on quota accounting; quotaoff to turn it off.
Actually both files are similar. They are executed at system startup
and shutdown.
This section describes how to enable file system quota on a Linux
host, assigning quota for users and groups, as well as the usage of
miscellaneous quota commands. It is intended for users running kernel
2.x (recently tested on kernel 2.4.21).
</para>
1. What is quota?
1.1. What is quota for?
<para>
Quota allows you to specify limits on two aspects of disk storage: the
number of inodes a user or a group of users may possess; and the
number of disk blocks that may be allocated to a user or a group of
users.
</para>
<para>
The idea behind quota is that users are forced to stay under their
disk consumption limit, taking away their ability to consume unlimited
disk space on a system. Quota is handled on a per user, per file
system basis. If there is more than one file system which a user is
expected to create files, then quota must be set for each file system
separately. Various tools are available for you to administer and
automate quota policies on your system.
</para>
1.2. Current Status of Quota on Linux
<para>
Currently, there are some major changes in the way quota works. There
are two different setups. The tools works the same, but there's a
difference in used files. This document describes the setup and
operation of the _new_ quota setup. As the new setup of quota is not
in the regular kernel source, this setup needs some patching. We will
describe this patching and installation of the linuxquota package. If
you already have the quota software installed on your system, you may
or may not have to install this patch and package. You can email me if
you have any questions about this. I'll try to include a overview of
Linux distro's and it's implications in a later version of this
document.
</para>
2. Requirements for quota
2.1. Kernel
<para>
The 2.x kernel source is available from http://www.kernel.org
<http://www.kernel.org/> Please use an available mirror close to your
location to save bandwidth. If you have a recent version of tar, you
can download the .bz2 compressed file.
</para>
<para>
Untar the kernel:
</para>
<para>
<screen>
______________________________________________________________________
cd /usr/src
tar jxvf /path/to/linux-2.4.21-tar.bz2 - for bzip2 kernel -
tar zxvf /path/to/linux-2.4.21-tar.gz - for gzip kernel -
ln -s /usr/src/linux-2.4.21 /usr/src/linux
______________________________________________________________________
</screen>
</para>
2.2. Quota software
<para>
Depending on the Linux distribution you have, you may, or may not have
the quota softwares installed on your system. The most recent version
of quota is available through SourceForge and is in active
development. You can reach the homepage of the quota-development at
http://www.sourceforge.net/projects/linuxquota
<http://www.sourceforge.net/project/linuxquota>.
</para>
3. Quota setup: installation and configuration
3.1. Patch the kernel
<para>
Download the patch for your kernel at:
</para>
<para>
ftp::/atrey.karlin.mff.cuni.cz/pub/local/jack/quota/
<ftp://atrey.karlin.mff.cuni.cz/pub/local/jack/quota/>.
</para>
<para>
Choose your kernel version and download the patch(es). Patch your
kernel with the 'patch' command. If there is more than 1 patch for
your kernel version, be sure to apply the patches in the correct
order.
</para>
<para>
You can use this script ( I assume the downloaded patches are in
/tmp/quota/ and the kernel has been untarred to /usr/src/linux) :
</para>
<para>
<screen>
______________________________________________________________________
#!/bin/sh
gunzip /tmp/quota/*.gz
cd /usr/src/linux
COUNT=`ls -1 /tmp/quota/*.diff | wc -l`
for I in `seq 1 $COUNT`
do
patch -p1 < /tmp/quota/quota-2.4.21-$I-*.diff
done
______________________________________________________________________
</screen>
</para>
3.2. Reconfigure your kernel
<para>
Reconfigure your kernel and add quota support.
</para>
<para>
Via `make menuconfig` or `make xconfig` you can find the option to
support quota under the Filesystems-menu. You can specify extra
options if you need them, like 32-bit UID support.
</para>
<para>
Save the configuration and compile the kernel. Make sure the new
kernel will be used when rebooting the system.
</para>
3.3. Compile and install the quota softwares
<para>
To be able to use all the features of the new quota system, you'll
probably need to download the new quota-package. Download the new
quota software via the URL provided above.
</para>
<para>
When downloaded do:
</para>
<para>
<screen>
______________________________________________________________________
$ gzip -dc <downloaded file> | tar xvf
$ cd quota-tools (or whatever directory the software is put in)
$ ./configure
$ make
$ su
# make install
______________________________________________________________________
</screen>
</para>
<para>
3.4. time Modify your system init script to check quota and turn
quota on at boot
</para>
<para>
Here's an example:
</para>
<para>
<screen>
______________________________________________________________________
# Check quota and then turn quota on.
if [ -x /usr/sbin/quotacheck ]
then
echo "Checking quotas. This may take some time."
/usr/sbin/quotacheck -avug
echo " Done."
fi
if [ -x /usr/sbin/quotaon ]
then
echo "Turning on quota."
/usr/sbin/quotaon -avug
fi
______________________________________________________________________
</screen>
</para>
<para>
The golden rule is that always turn quota on after your file systems
in /etc/fstab have been mounted, otherwise quota will fail to work. I
recommend turning quota on right after the part where file systems are
mounted in your system init script.
</para>
3.5. Modify /etc/fstab
<para>
Partitions that you have not yet enabled quota normally look something
like:
</para>
<para>
<screen>
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults 1 1
______________________________________________________________________
</screen>
</para>
<para>
To enable user quota support on a file system, add "usrquota" to the
fourth field containing the word "defaults" (man fstab for details).
</para>
<para>
<screen>
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota 1 1
______________________________________________________________________
</screen>
</para>
<para>
Replace "usrquota" with "grpquota", should you need group quota
support on a file system.
</para>
<para>
<screen>
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,grpquota 1 1
______________________________________________________________________
</screen>
</para>
<para>
Need both user quota and group quota support on a file system?
</para>
<para>
<screen>
______________________________________________________________________
/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota,grpquota 1 1
______________________________________________________________________
</screen>
</para>
3.6. Activate the quota system
<para>
To activate the quota software you have to reboot the system for the
changes you have made to take effect. The new kernel with quota
support will be loaded and the startup scripts you've just created
will be executed. At first run, quotacheck will generate the
appropiate files to maintain the quota databases.
</para>
3.7. Add quotacheck to crontab
<para>
Although quota should work with periodical checks, it sometimes helps
to run quotacheck periodically, e.g. weekly. Add the following line to
your root's crontab:
</para>
<para>
<screen>
______________________________________________________________________
0 3 * * 0 /sbin/quotacheck -avug
______________________________________________________________________
</screen>
</para>
4. Quota setup: tools
<para>
This operation is performed with the edquota command (`man edquota`
for details).
</para>
4.1. Assigning quota for a particular user
<para>
Here's an example. I have a user with the login id bob on my system.
The command "edquota -u bob" takes me into vi (or editor specified in
my $EDITOR environment variable) to edit quota for user bob on each
partition that has quota enabled:
</para>
<para>
<screen>
______________________________________________________________________
Quotas for user bob:
/dev/hda3: blocks in use: 2594, limits (soft = 5000, hard = 6500)
inodes in use: 356, limits (soft = 1000, hard = 1500)
______________________________________________________________________
</screen>
</para>
<para>
"blocks in use" is the total number of blocks (in kilobytes) a user
has consumed on a partition.
</para>
<para>
"inodes in use" is the total number of inodes a user has consumed on a
partition.
</para>
4.2. Assigning quota for a particular group
<para>
Now I have a group games on my system. "edquota -g games" takes me
into the vi editor again to edit quota for the group games:
</para>
<para>
<screen>
______________________________________________________________________
Quotas for group games:
/dev/hda4: blocks in use: 5799, limits (soft = 8000, hard = 10000)
inodes in use: 1454, limits (soft = 3000, hard = 4000)
______________________________________________________________________
</screen>
</para>
4.3. Assigning quota for a bunch of users with the same value
<para>
To rapidly set quotas for, say 100 users, on my system to the same
value as my user bob, I would first edit bob's quota information by
hand, then execute:
</para>
<para>
<screen>
______________________________________________________________________
edquota -p bob `awk -F: '$3 > 499 {print $1}' /etc/passwd`
______________________________________________________________________
</screen>
</para>
<para>
assuming that you are using csh, and that you assign your user UID's
starting with 500.
</para>
<para>
In addition to edquota, there are 3 terms which you should familiarize
yourself with: Soft Limit, Hard Limit, and Grace Period.
</para>
4.4. Soft Limit
<para>
_Soft limit_ indicates the maximum amount of disk usage a quota user
has on a partition. When combined with grace period, it acts as the
border line, which a quota user is issued warnings about his impending
quota violation when passed.
</para>
4.5. Hard Limit
<para>
Hard limit works only when grace period is set. It specifies the
absolute limit on the disk usage, which a quota user can't go beyond
his hard limit.
</para>
4.6. Grace Period
<para>
Executed with the command "edquota -t", grace period is a time limit
before the soft limit is enforced for a file system with quota
enabled. Time units of sec(onds), min(utes), hour(s), day(s), week(s),
and month(s) can be used. This is what you'll see with the command
"edquota -t":
</para>
<para>
<screen>
______________________________________________________________________
Time units may be: days, hours, minutes, or seconds
Grace period before enforcing soft limits for users:
/dev/hda2: block grace period: 0 days, file grace period: 0 days
______________________________________________________________________
</screen>
</para>
<para>
Change the 0 days part to any length of time you feel reasonable. I
personally would choose 7 days (or 1 week).
</para>
5. Miscellaneous Quota Commands
5.1. Quotacheck
<para>
Quotacheck is used to scan a file system for disk usages, and updates
the quota record file "aquota.user" to the most recent state. I
recommend running quotacheck at system bootup, and via cronjob
periodically (say, every week?).
</para>
5.2. Repquota
<para>
Repquota produces a summarized quota information for a file system.
Here is a sample output repquota gives:
</para>
<para>
<screen>
______________________________________________________________________
# repquota -a
Block limits File limits
User used soft hard grace used soft hard grace
root -- 175419 0 0 14679 0 0
bin -- 18000 0 0 735 0 0
uucp -- 729 0 0 23 0 0
man -- 57 0 0 10 0 0
user1 -- 13046 15360 19200 806 1500 2250
user2 -- 2838 5120 6400 377 1000 1500
______________________________________________________________________
</screen>
</para>
5.3. Quotaon and Quotaoff
<para>
Quotaon is used to turn on quota accounting; quotaoff to turn it off.
Actually both files are similar. They are executed at system startup
and shutdown.
</para>
</sect1>

37
LDP/guide/docbook/Linux-Networking/RAID.xml
View File

@ -3,6 +3,43 @@
<title>RAID</title>
<para>
10.2. RAID
RAID, short for Redundant Array of Inexpensive Disks, is a method
whereby information is spread across several disks, using techniques
such as disk striping (RAID Level 0) and disk mirroring (RAID level 1)
to achieve redundancy, lower latency and/or higher bandwidth for
reading and/or writing, and recoverability from hard-disk crashes.
Over six different types of RAID configurations have been defined.
There are three types of RAID solution options available to Linux
users: software RAID, outboard DASD boxes, and RAID disk controllers.
· Software RAID: Pure software RAID implements the various RAID
levels in the kernel disk (block device) code.
· Outboard DASD Solutions: DASD (Direct Access Storage Device) are
separate boxes that come with their own power supply, provide a
cabinet/chassis for holding the hard drives, and appear to Linux as
just another SCSI device. In many ways, these offer the most robust
RAID solution.
· RAID Disk Controllers: Disk Controllers are adapter cards that plug
into the ISA/EISA/PCI bus. Just like regular disk controller cards,
a cable attaches them to the disk drives. Unlike regular disk
controllers, the RAID controllers will implement RAID on the card
itself, performing all necessary operations to provide various RAID
levels.
Related HOWTOs:
· http://metalab.unc.edu/mdw/HOWTO/mini/DPT-Hardware-RAID.html
· http://metalab.unc.edu/mdw/HOWTO/Root-RAID-HOWTO.html
· http://metalab.unc.edu/mdw/HOWTO/Software-RAID-HOWTO.html
RAID at linas.org:
· http://linas.org/linux/raid.html
RAID, short for Redundant Array of Inexpensive Disks, is a method
whereby information is spread across several disks, using techniques
such as disk striping (RAID Level 0) and disk mirroring (RAID level 1)

7
LDP/guide/docbook/Linux-Networking/Satellite.xml
View File

@ -1,3 +1,7 @@
<sect1 id="Satellite">
<title>Satellite</title>
Sat (Satellite Technology) HOWTO
Roberto Arcomano berto@fatamorgana.com, Florindo Santoro
flosan@hack-it.net
@ -1474,5 +1478,4 @@
http://www.fatamorgana.com <http://www.fatamorgana.com>
</sect1>

12
LDP/guide/docbook/Linux-Networking/Sources.xml
View File

@ -1141,5 +1141,15 @@ who we should thank for writing the first versions of this document.
output''.
2002-10-08: Added section ``Actual configuration'' and hints about
routing in ``Setting up the routing'', ``Ping it, Jim!'' , resp.
The Clock Mini-HOWTO
Ron Bean, rbean@execpc.com
v2.1, November 2000
1.3. Acknowledgements
This mini-HOWTO has been greatly improved thanks to various people who
have sent me email since the first version in 1996. In some cases
they wrote with questions but ended up giving me as much information
as I gave them. Unfortunately I haven't compiled a list of names
(maybe next time). You know who you are :-).
</appendix>