How to Increase the Size of the RAMFS with chramfs


About this document

About this document

This document describes how to increase the size of the random access memory filesystem (RAMFS) with the chramfs command. The following method is used when the restore fails with an out of space error message. This method only applies to situations where the system is booted from a Sysback bootable image (tape or network) for a rootvg installation from a Sysback full system backup. Once booted from the bootable image, only a certain amount of the system's RAM is allocated to the newly created virtual filesystem (or RAMFS) that the AIX installation image (basically a mini-kernel) uses. Although methods exist to alter the default amount of RAM used by the RAMFS prior to the bootable image being created, there is no way to increase the size of the RAMFS after bootup except by employing the /usr/lib/boot/chramfs AIX command. This document discusses how to use this command with a system booted from a Sysback boot image.

This document applies to all in-service versions of Sysback on any supported AIX version.


  1. If the backup was made at Sysback version or later, then skip to step 4. Otherwise, choose a system on which to build the floppy. This system should be at the same level of AIX as is contained in the boot image. On a local tape boot, the chosen system should be at the same OS level as that of the source system at the time the backup was taken. On a network boot, the chosen system should be at the same OS level as that of the boot server.

  2. Place an initialized floppy in the drive of the chosen system.

  3. Enter the following series of commands:
    	cd /usr/lib/boot
    	chmod 775 chramfs
    	backup -ivqf /dev/fd0 ./chramfs

  4. Boot the destination machine from Sysback.

  5. When prompted, choose your console. Wait for the machine to display the Installation and Maintenance MAIN MENU.

  6. Choose the Maintenance Shell option. (For Sysback Version 4.2 and later ONLY, choose Utilities Menu first.)

  7. Place the floppy in the drive.

  8. For Sysback versions and higher, enter the following commands:
            cd /usr/lib/boot

    For all earlier versions of Sysback, enter the following commands:

    	cd /tmp
    	restore -xqf /dev/fd0

  9. Verify the current size of the RAM filesystem by entering the df command.

  10. Increase the size of the RAM filesystem by two megabytes. Enter:
    	chramfs 4096

  11. Verify that the RAM filesystem has increased in size. Enter the df command.

  12. Return to the Sysback menus. Enter:

[ Doc Ref: 9278380038546     Publish Date: Aug. 14, 2000     4FAX Ref: 4392 ]