su -m fails if user has shell set to /bin/false

Odin_SE · n00b Joined: 27 Oct 2006 Posts: 14

Hi,

I'm working with unattended backup using rdiff-backup and part of the instructions are to set up a user account, say backup, with no password and shell set as /bin/false.

A little later in then instructions you su -m backup. This does not give any errors but I am not su'd to backup.
If I then change passwd such that backup's shell is /bin/bash, it all works fine.

Can anyone explain why this is happening?

My only idea is that it's because I'm running hardened (2.6.20-hardened-r10).

The rdiff-backup instructions that I'm following are here:

http://arctic.org/~dean/rdiff-backup/unattended.html

It's at 2. that the su instructions start.

Any help appreciated.

//Odin

eccerr0r · Posted: Fri Dec 14, 2007 11:58 pm Post subject:

I think it's because it's probably executing /bin/false and returning to root real quick.

Try

Odin_SE · n00b Joined: 27 Oct 2006 Posts: 14

That worked nicely.
I just wonder why it was failing though...

From the su docs:

-m
Do not change the environment variables `HOME', `USER', `LOGNAME',
or `SHELL'. Run the shell given in the environment variable
`SHELL' instead of the shell from USER's passwd entry, unless the
user running `su' is not the superuser and USER's shell is
restricted. A "restricted shell" is one that is not listed in the
file `/etc/shells', or in a compiled-in list if that file does not
exist. Parts of what this option does can be overridden by
`--login' and `--shell'.

When I do echo $shell, it says /bin/bash and I'm changing from superuser so it should have worked. No matter, this fixes the problem