Difference between revisions of "Disk Limits and Quota"

Revision as of 23:53, 10 July 2009

Introduction

We call Disk Limit a disk space limit in a filesystem for one context (i.e. VServer). If you are interested in using user/group quotas inside a VServer, this is not the right place, look at the Quotas page.

Of course, you can also use a dedicated partition (or logical volume) for each guest, which is another way to limit disk space usage per guest.

Activating disk limits

For VServer version 2.0, please read http://oldwiki.linux-vserver.org/Disk+Limits

For VServer 2.2+, the procedure is nearly the same, only the mount option has changed:

1. Activate the XID tagging on the filesystem hosting the VServer, using the tag mount option. You cannot use the remount option to add the tag on an already mounted filesystem. Be warn, it is not advised to use it on the root filesystem! In the next example, we use the /dev/sdb1 partition to host all the guests, under the /vservers directory

   mount -o tag /dev/sdb1 /vservers

2. Consider modifying your /etc/fstab file if necessary, to make the mount option persist across reboots
3. Tag the files belonging to the VServer with its XID

   chxid -URx -c vs_name /vservers/vs_name 

4. Write the limits under the /etc/vservers/vs_name/dlimits directory :
   1. Create this directory if necesary
   2. Create one sub-directory for each filesystem (in most cases, you should have only one), using any identifier (for example root)
   3. Under /etc/vservers/vs_name/dlimits/root/ create the following files :
      1. directory : contains the directory to which the limit should be applied
      2. inodes_total : the amount of inodes this vserver should be limited to
      3. reserved : how much space (percentage-wise) should be reserved for the root user
      4. space_total : the amount of space this vserver should be limited to (measured in blocks of 1024 bytes)

Controling disk limits

After starting your VServer, you can control the actual limit using the vdlimit command (in this example, 300 is the context number associated with vs_name) :

 # vdlimit --xid vs_name /vservers
 300 /vservers
 space_used=154604
 space_total=204800
 inodes_used=7834
 inodes_total=100000
 reserved=5

You can also use the vdu command to count space or inodes used by a specific guest

 # vdu --xid vs_name --space /vservers
 /vservers 154604
 # vdu --xid vs_name --inodes /vservers
 /vservers 7834

If you just want to update disk usage of a guest activating disk limits, then you can use this script. It will count the usage of all files and update the limits:

 #/bin/sh
 _dir=/var/lib/vservers
 if [ ! -d $_dir/$1 ]; then
     echo no such vserver
     exit 1;
   fi;
 chxid -URx -c $1 $_dir/$1
 vdlimit --xid $1 -s space_used=$(vdu --xid $1 --space $_dir/$1 | cut -d" " -f2) $_dir/$1
 vdlimit --xid $1 -s inodes_used=$(vdu --xid $1 --inode $_dir/$1 | cut -d" " -f2) $_dir/$1

More information

• See also dlimits on the util-vserver homepage http://www.nongnu.org/util-vserver/doc/conf/configuration.html
• For information about limiting diskspace with XFS, please see the XFS page.