Detecting and Fixing Underlying Mount Point Permission Errors on AIX
brian_s 270002K5X3 Comment (1) Visits (17695)
Every Filesystem in AIX has two sets of permissions: The permissions on the mount point directory, and the permissions on the mounted filesystem.
Here is an example:
Normally the Mount Point Permissions don't come in to play once the filesystem is mounted (how
However, if a user doesn't have read/execute permissions on the mount point you will see weird behavior and frequently have application issues as well.
Here is an example showing this:
As a non-root user, we do an "ls -al" in the directory and get a weird "./..: Permission denied" error. This is caused because the underlying mount point permissions are restricted (700) and the user doesn't have read/execute permissions on the underlying mount point (even though the mounted filesystem has 777 permissions).
Now there are 2 different ways to check to see what the permissions are on the underlying mount points of your filesystems. You can unmount the filesystem, and do an "ls -ald" on the mount point (but it will probably require application downtime to unmount the filesystem...) Or you could use this handy script that will show you the underlying mount point permissions while the filesystem is online and mounted.
Just a quick disclaimer however... These scripts have worked with my limited testing; but use them at your own risk. The IBM documentation always recommends unmounting the filesystem to check or change mount point permissions and this is the safest and best way to do it. These scripts will do everything with the filesystem mounted and online.
When run, it will show you the underlying mount point permissions for all mounted JFS/JFS2 filesystems:
If you have filesystems with too restrictive mount points that are causing you issues (like /test1 and /app2 in the example above), then you can either unmount the filesystem and change the mount point permissions, or use this script to add read/execute permissions to user/group/others on the underlying mount point directory while it is still mounted and online:
With the script you specify a filesystem and it will add the read/execute permissions on the underlying mount point: