Reducing the Size of the /var or /tmp File System


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Sample of etc/filesystems stanzas

About this document

The information contained in this document concerns reducing the size of the /var or /tmp file system.
This document applies to all supported releases of AIX Version 4.

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The following steps reduce the size of the /var or /tmp file system in all supported releases of AIX Version 4. If either file system on your machine is 8192KB in size or smaller, you probably should not reduce it. The default size of the /var file system (on installation) is 4096KB, which fills up rather quickly. If you can afford the space, it is better to have /var be 8192KB total. The default size of the /tmp file system (upon installation) is 8192KB.

NOTE: Back up the data before proceeding. If you have a tape drive connected to your system, this can be achieved by executing the following sequence of commands on either /var or /tmp:

    cd / 
    tar -cvf /dev/rmt0 /var 

/dev/rmt0 can be replaced with /dev/fd0 or the full path of a directory NOT in the same file system.

  1. Boot your system into a limited function maintenance shell (Service or Maintenance mode) from bootable AIX media.

    Please refer to your system user's or installation and service guide for specific IPL procedures related to your type and model of your system. Additionally, the document titled "Booting in Service Mode", available at, has specific procedures for most types of systems.

  2. With bootable media of the same version and level as the system, boot the system into Service mode.

    The bootable media can be any ONE of the following:

    Follow the screen prompts or icons to the Welcome to Base OS menu.

    1. Choose Start Maintenance Mode for System Recovery (Option 3). The next screen displays prompts for the Maintenance menu.

    2. Choose Access a Root Volume Group (Option 1).

      The next screen displays a warning that indicates you will not be able to return to the Base OS menu without rebooting.

    3. Choose 0 continue.

      The next screen displays information about all volume groups on the system.

    4. Select the root volume group by number. The logical volumes in rootvg will be displayed with two options below.

    5. Choose Access this volume group and start a shell. (Option 1).

    If you get errors from the preceding option, do not continue with this procedure. Correct the problem causing the error. If you need assistance correcting the problem causing the error, contact one of the following:

    If no errors occur, proceed with the following steps.

  3. Unmount the file system. (The following examples use /var. If you intend to reduce the /tmp file system, substitute /tmp for /var in the commands.) Execute:
        umount /var
  4. Remove the file system by executing:
        rmfs /var

  5. Determine the physical partition (PP) size of your rootvg volume group with the command:
       lsvg rootvg
  6. Create the logical volume with one of these commands:

        mklv -y hd9var rootvg [x]     (for /var)
        mklv -y hd3 rootvg [x]           (for /tmp)

    x is the number of logical partitions you want to allocate. If your rootvg volume group has a PP size of 4MB, and you want the /var file system to be a total of 8MB in size, then x would be 2. For example:

        mklv -y hd9var rootvg 2 

    This command makes a logical volume hd9var of size 8MB (two 4MB partitions) in the rootvg volume group.

    NOTE: The hd3 is the logical volume name used for the /tmp file system, and hd9var is the logical volume name used for /var. These names must be used if you wish to maintain your AIX system in an IBM supported state.

  7. Create the file system with the following command:
        crfs -v jfs -d hd9var -m /var -a check=false -a free=false -a vol=/var

    NOTE: Substitute hd3 for hd9var and /tmp for /var if needed. Refer to the section Example of /etc/filesystems for the different attributes required for these filesystems.

  8. Mount the file system:

        mount /var       (OR    mount /tmp)

  9. If you are recreating /var, now create the /var/tmp directory for the vi editor. Execute:
        mkdir /var/tmp 
  10. Set your TERM variable and export it. If you are using a megapel display, try setting TERM=hft. If you are using an ASCII terminal such as an IBM 3151, set your TERM to the appropriate terminal type. For example:
        export TERM 
  11. Edit /etc/filesystems. If you have been recreating /tmp, invoke the vi editor by executing the following command:
        vi -c "set dir=/" /etc/filesystems 

    If you have not been recreating /tmp, execute:

        vi /etc/filesystems 

    Skip down to the stanza for either /var or /tmp. Within that stanza, go to the line that says mount = false and change the word false to automatic. Save the file.

  12. Change the ownership and permissions to the proper values, as follows:
        chmod g-s /var 
        chmod 755 /var 
        chown bin.bin /var
        chmod g-s /tmp 
        chmod 1777 /tmp 
        chown bin.bin /tmp 
  13. Restore the files from your backup. If you used the backup method given earlier in this document, execute:
        cd / 
        tar -xvf /dev/rmt0 
  14. Remove the bootable media if you have not already done so.

  15. If your system has a mode select key, switch it to the Normal position.

  16. Reboot the system into Normal mode with the following:

Sample of /etc/filesystems stanzas for AIX V4


	dev             = /dev/hd9var
       	vfs             = jfs
       	log             = /dev/hd8
	mount           = automatic
	check           = false
	type            = bootfs
	vol             = /var
	free            = false


	dev             = /dev/hd3
	vfs             = jfs
	log             = /dev/hd8
	mount           = automatic
	check           = false
	vol             = /tmp
	free            = false

[ Doc Ref: 90605221114602     Publish Date: Jan. 17, 2001     4FAX Ref: 7204 ]