Remote execution via ssh hangs if X11 is enabled

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AsstInverter
Posts: 7
Joined: 2020/07/30 10:28:52

Remote execution via ssh hangs if X11 is enabled

Post by AsstInverter » 2021/07/26 13:51:29

We've recently upgraded to CentOS 8.4.2105.

If using ssh to execute a command remotely on these systems, the connection hangs if enabling X.

From macOS 11.5 (the problem exists from Scientific Linux 6 and from CentOS 8.4.2105 itself as well.):

Code: Select all

% ssh -x centosserver01 date  
Mon Jul 26 15:47:13 CEST 2021
works fine, whereas:

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% ssh -Yvvv centosserver01 date
...
debug3: channel 0: status: The following connections are open:
  #0 client-session (t4 r0 i3/0 o3/0 e[write]/0 fd -1/-1/8 sock -1 cc -1)
  #1 x11 (t4 r3 i0/0 o0/0 e[closed]/0 fd 9/9/-1 sock 9 cc -1)
  #2 x11 (t4 r4 i0/0 o0/0 e[closed]/0 fd 10/10/-1 sock 10 cc -1)
hangs until Ctrl+C is pressed.

A few google searches have led me to believe it has to do with the spawning of DBUS, and the inability to close this session again.

AsstInverter
Posts: 7
Joined: 2020/07/30 10:28:52

Re: Remote execution via ssh hangs if X11 is enabled

Post by AsstInverter » 2021/07/27 07:39:20

I just checked with a bone stock CentOS 8.4.2105, and the problem persists.

I think it has to do with dbus-deamon and dbus-launch.

AsstInverter
Posts: 7
Joined: 2020/07/30 10:28:52

Re: Remote execution via ssh hangs if X11 is enabled

Post by AsstInverter » 2021/07/27 13:55:27

Just checked, this is a regression from 8.3.2011 to 8.4.2105.

One needs to install "Server with GUI" to replicate the problem, probably because of DBUS.

The simplest test is to just ssh to the machine itself:

Code: Select all

ssh -X localhost uptime

AsstInverter
Posts: 7
Joined: 2020/07/30 10:28:52

Re: Remote execution via ssh hangs if X11 is enabled

Post by AsstInverter » 2021/08/05 19:29:17

Turns out the issue is a known one, and is tracked here: https://bugzilla.redhat.com/show_bug.cgi?id=1972266

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