CentOS - Apr 2021 - rsync over ssh stalls after completing the job

> On Tue, 13 Apr 2021 12:09:42 -0700 (PDT)
> Paul Heinlein wrote:
>
>> Is there any chance that your shell is configured to emit anything to
>> stderr or stdout when you logout of jeff? It's fairly rare, but
I've
>> seen logout messages mess up rsync before.
>
> I don't think so.  The only change from the default .bashrc on both
> machines is the addition of "unset command_not_found_handle", and
in
> .bash_profile on mutt I have xmodmap -e "keycode 135 = 0x0000",
which
> hasn't changed since 2016 according to the timestamp on the file. 
Other
> than that, the .bash* files are just the defaults.  sshd_config has
> nothing other than the default settings for logout messages, and in any
> event none of these things have changed since last week and it did work
> then.
>
> I wonder if it's something to do with the last Centos 8 update.  There
was
> a fair amount of stuff updated including the kernel.  I just rebooted both
> machines with the previous kernel and nothing changed, so that doesn't
> appear to be it either.
>
You could try running strace on the hanging process so see what it's doing.

Regards,
Simon

On Tue, 13 Apr 2021 22:29:26 +0200
Simon Matter wrote:
> You could try running strace on the hanging process so see what it's
doing.
[frankcox at mutt temp]$ rsync -avv ../temp/ jeff:temp
opening connection using: ssh jeff rsync --server -vvlogDtpre.iLsfxC . temp  (7
args)
sending incremental file list
delta-transmission enabled
abc is uptodate
total: matches=0  hash_hits=0  false_alarms=0 data=0

Leaving that sit there apparently doing nothing (but still not giving me my
cursor back) I switched to another terminal window and did the following:

[frankcox at mutt ~]$ ps -FA | grep rsync
frankcox    5400    2435  0 60586  3160   5 14:52 pts/0    00:00:00 rsync -avv
../temp/ jeff:temp
frankcox    5401    5400  0 67980  7440   1 14:52 pts/0    00:00:00 ssh jeff
rsync --server -vvlogDtpre.iLsfxC . temp
frankcox    5526    5416  0 55476  1076   3 14:53 pts/1    00:00:00 grep
--color=auto rsync

[frankcox at mutt ~]$ strace -p 5401
strace: Process 5401 attached
select(11, [5 9 10], [], NULL, NULL

Then it just sits there with no further action.  I get my cursor back when I hit
ctrl-c.

[frankcox at mutt ~]$ strace -p 5400
strace: Process 5400 attached
restart_syscall(<... resuming interrupted nanosleep ...>) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0
nanosleep({tv_sec=0, tv_nsec=20000000}, NULL) = 0
wait4(5401, 0x7ffd45105564, WNOHANG, NULL) = 0

The wait4-etc line just keeps repeating endlessly until I hit ctrl-c.

Unfortunately, I have no idea what any of the above actually means.  Does it
tell us anything interesting?


-- 
MELVILLE THEATRE ~ Real D 3D Digital Cinema ~ www.melvilletheatre.com