This document discusses the device files in the /dev directory for each logical volume (LV), and the circumstances under which the permissions for these device files would change (especially Raw LV's). This document assumes that the permissions, owner, group, etc. were changed manually to suit the needs of a database application that accesses these logical volumes.
This document applies to AIX versions 4.x.
For more information related to this document see:
The synclvodm command:
Storage Management Guide (in PDF format):
The product documentation library is also available:
There are two device files in the dev directory for each logical volume.
For example, enter ls -l /dev/lv00 /dev/rlv00.
brw-rw---- 1 root system 42, 3 May 12 07:29 lv00 crw-rw---- 1 root system 42, 3 May 12 07:29 rlv00
The b at the beginning of the line indicates a block device. The c indicates a character device.
The default permissions for these files are 660 and are owned by root. The group is system.
Some database applications need these device files to be owned by the application or by another user. If the permissions are changed, the device files may look something like the following:
brw-rw-rw- 1 oracle database 42, 3 May 12 05:30 lv00 crw-rw-rw- 1 oracle database 42, 3 May 12 05:30 rlv00
Since there is no way to retain these permissions if you need to remove and recreate these device files, they are brought back to system defaults when certain commands are executed.
NOTE: Some changes made in AIX 4.3.2 store these permissions, as explained in the section "Enhancements in AIX version 4.3.2."
Some possible reasons for the recreation of the device files are:
In AIX version 4.3.2, there have been enhancements to the mklv and the chlv commands which store these permissions. Even if the volume group is in an exported state, and you import the volume group back in using the -R flag with importvg, all the permissions are retained.
NOTE: These changes can be made only if the volume group that contains these logical volumes is in big VG format, as these permissions are stored in the Volume Group Descriptor Area (VGDA). Check the man pages for mkvg and chvg for the new flags that enable you to create big Volume Groups.
Following are the new flags added to mklv and chlv:
NOTE: If the volume group is exported and needs to be imported, the -R flag must be used with importvg. If the synclvodm command is run, you must still use the -P flag to retain the permissions.
If the volume group is imported without the -R flag, you can still export the volume group. Import again using the -R flag, and the permissions will be retained. However, if synclvodm is run without the -P flag, rerunning this command with the -P flag will not change the permissions back to what you want them to be, and they will remain at system defaults.
[ Doc Ref: 95486132612738 Publish Date: Oct. 02, 2000 4FAX Ref: 8493 ]