AIX, user gets “pwd: The file access permissions do not allow the specified action.”

Just a short demonstration that file permissions matter on directories used as mount points under AIX6.1. Let’s say we have properly running system, the oracle software owner user “orand3″ can access everything (pwd and ls commands):

Now we simulate how the underneath mount point permission affects the users after mounting:

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As you can see it changed ownership from orand3:dba to root:system after unmounting (because in reality after unmounting /oracle/ND3/102_64 is just a directory on higer level filesystem like /oracle or /oracle/ND3):

OK, we want to show how the normal (i.e. non-root users) react to mount point directory that is not allowing access for them:

See?, after the mounting it changed to 755 orand3:dba , but underneath it is still root:system with 700. So what should do the AIX kernel perform ? Let’s see…

As it was demonstrated underneath mount point permission DO HAVE an affect on non-root users for pwd command if they are not clearly visible. What’s even more interesting that typical libc routines for opening dir, reading dor – they works just fine. It is just a matter of pwd command.

Ok – let’s fix it…

So what is really pwd command doing?

So you have an interal pwd command (for shell) but also real command in /usr/bin. Let’s see what’s happening there:

So the the truth is hidden in EACCES return code for the statx() syscall.

As you saw if you are planning some non-root users (e.g. Oracle in this case) to properly work on mounted filesystems under AIX you need to have proper permissions on the mount point dir first before mounting. Ther e is no escape from this. All comes to the definition of the stat() faimiliy of system calls:

“Searchable” for directory in UNIX means “+x” , so someone has to have execute bit set (+x) on the directory in order it to be searchable for system calls.