wierd problem with prefdm, can't exec from /etc can from /tmp

[a8hex]

I've just installed Fedora 8 onto a USB 4GB key. Everything when great, I left it updating last night and then let it reboot this morning. When I did this however X didn't startup. On the console I just get

init: Id "x" respawning too fast: disabled for 5 minutes

So I go and take a look at the inittab file, and it's trying to execute

[root@duck ~]# grep ^x /etc/inittab
x:5:respawn:/etc/X11/prefdm -nodaemon

So I try this from a ssh session, I just get the prompt back.
After checking the file, I see it's a shell script so I try

sh -xv /etc/X11/prefdm -nodaemon

and it starts no problem.
I try adding a

set -xv

into the script to see where it fails ...

# Fallbacks, in order
exec gdm "$@" >/dev/null 2>&1 </dev/null
+ exec gdm -nodaemon

So it's trying to exec gdm.

Before I make any further changes to the script I copy it to /tmp and try things from there. It works no problem.

cp /etc/X11/prefdm /tmp
/tmp/prefdm -nodaemon

works with no problem

/etc/X11/prefdm -nodaemon

the exec fails.


hmmm I'm confused!

[a8hex]

OK, I tried another test.

cp /etc/X11/prefdm /etc/X11/prefdm2
/etc/X11/prefdm2 -nodaemon

also works fine.

[jnilsson]

We had a similar issue with Oracle Linux (Red Hat). I believe that the issue was related to GDM...

I believe that I fixed it by reinstalling GDM using yum.

[a8hex]

Thanks for the response.

I can get it to work, just by making a copy of the script, what I don't understand is why I get such different behaviour from a couple of copies of a shell script.

When I run /etc/X11/prefdm -nodaemon

The script execs

gdm -nodaemon,

and looking at the output this generates I get

/etc/X11/prefdm: /usr/sbin/gdm: /bin/sh: bad interpreter: Permission denied
/etc/X11/prefdm: line 38: /usr/sbin/gdm: Success
exec kdm "$@" >/dev/null 2>&1 </dev/null
+ exec kdm -nodaemon

Yet the copy of the script (prefdm2)
gives the expected


test -f /etc/profile && . /etc/profile
+ test -f /etc/profile
+ . /etc/profile
# /etc/profile
...

Which is the stuff at the start of the gdm script


The prefdm instance is actually not getting a far as executing gdm at all.

If I remove all the output redirections so I get the end of prefdm looking like.

### [ -n "$preferred" ] && exec $preferred "$@" >/dev/null 2>&1 </dev/null
[ -n "$preferred" ] && exec $preferred "$@" </dev/null

# Fallbacks, in order
exec gdm "$@" </dev/null
exec kdm "$@" </dev/null
exec wdm "$@" </dev/null
exec xdm "$@" </dev/null
# catch all exit error
exit 1


Then running it I get

### [ -n "$preferred" ] && exec $preferred "$@" >/dev/null 2>&1 </dev/null
[ -n "$preferred" ] && exec $preferred "$@" </dev/null
+ '[' -n '' ']'

# Fallbacks, in order
exec gdm "$@" </dev/null
+ exec gdm -nodaemon
/etc/X11/prefdm: /usr/sbin/gdm: /bin/sh: bad interpreter: Permission denied
/etc/X11/prefdm: line 38: /usr/sbin/gdm: Success
exec kdm "$@" </dev/null
+ exec kdm -nodaemon
/etc/X11/prefdm: line 39: exec: kdm: not found
exec wdm "$@" </dev/null
+ exec wdm -nodaemon
/etc/X11/prefdm: line 40: exec: wdm: not found
exec xdm "$@" </dev/null
+ exec xdm -nodaemon
/etc/X11/prefdm: line 41: exec: xdm: not found
# catch all exit error
exit 1
+ exit 1
[root@duck ~]#


Don't worry about the failure of kdm et al... I don't think they are installed.

but

/etc/X11/prefdm: /usr/sbin/gdm: /bin/sh: bad interpreter: Permission denied
/etc/X11/prefdm: line 38: /usr/sbin/gdm: Success

has me confused.
Why is it saying that it's getting permission denied from /bin/sh ?

You get the same type of error message if you start a script with

#!/home/ken/file

when file exists but does not have execute permission.

Could this be some "SE" Linux feature?

Cheers
Ken

[jnilsson]

It could be several things:

1. That the GDM startup scripts got corrupted during the update.
2. The SELinux polices got corrupted during the update.

Thats why I advised you to try to reinstall GDM and see if it recreates the scripts that are causing the issue.

J

[a8hex]

The GDM startup scripts work fine.

I think it's the SE Linux policy. Digging into this there is an entry for prefdm.
I don't really understand the SELinux stuff. but prefdm has an SE File type of initrc_exec_t:s0

[jlumpkins]

I'm having the same problem...

Fedora 8 fresh install
Worked fine until I installed the updates.
I can hit the return after x dies, after the respawn message, and then log in, and startx with no problems.
I have downloaded and installed NVidia's driver, but the same driver works great when I boot from a different harddrive that has my Fedora 7 on it.

Also, only refresh rates available under the Screen Resolution Preferences is 50, and 51 Hz. It's 60 in Fedora 7.

I've:
1. made a copy of /etc/X11/prefdm, then replaced the original with the copy; Didn't help
2. relabeled the entire file system on reboot for SE Linux; didn't help.
3. changed SELInux to permissive; Didn't help.
4. replaced my /etc/X11/xorg.conf with the one from my Fedora 7 install; Didn't help.
5. installed the latest updates as of tonight; Didn't help.

I'm open to suggestions...

(x86_64; NVidia 7600GT; Core2 Dual 2.66)

Everything works fine in Fedora 7.

[jlumpkins]

Ok, I finally solved it.

I'm not certain why when I did a yum info gdm it showed it as installed,
but, when I ran yumex, and searched for gdm, it did not list it as installed,
and I checked the box, and updated.

Everything is working now...