su starts behaving oddly sometimes on F19

Jan Synacek jsynacek at
Fri May 17 06:14:20 UTC 2013

On 05/17/2013 07:29 AM, Adam Williamson wrote:
> This is a weird bug I've seen 3 or 4 times since upgrading to F19, and
> am having trouble pinning down.
> Occasionally, after my session has been up for some time, runs of 'su'
> start behaving oddly. After I enter the root password, it takes a long
> time - longer than the delay that's always happened when you fat-finger
> your password, even - before it succeeds. Usually, of course, it's
> instant. But when this bug happens, I just get to sit there while it
> thinks about it for like 10-15 seconds before I eventually get a root
> prompt.
> This only applies to my desktop session - but it applies to any terminal
> running in the desktop. At least, it applies to gnome-terminal (even if
> closed and opened again) and xterm. But if I go to ctrl-alt-f2, login,
> and run an 'su', that still returns instantly.
> I've tried strace'ing su, but interestingly, I can't get it to work:
> running su via strace always seems to result in "Authentication
> failure" (which doesn't display this bug; it's only _normally_ slow, the
> same slowness that has always been the case when you fail the password).
> So I'm kinda stuck, really. Has anyone else seen this? Any bright ideas
> for debugging it? Thanks!

Just a guess, but is your shell a subprocess of sssd? I have no idea if that
might have any influence. But, I noticed, that on my machine, all of my bash
processes are spawned via sssd, even though I didn't configure or even enable
it. If that or anything similar happened in your case, I wouldn't be surprised
that your shell is waiting for some timeouts while doing authentication that you
might not know about. Again, that's just a wild guess.

Jan Synacek
Software Engineer, Red Hat

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