[systemd-devel] rghvk at outlook.com

[Aravindhan Krishnan]

Adding Raghav.

And sorry the subject should have stated: Discrepancy in using dhclient b/w
ubuntu 20.04 and ubuntu 16.04

Regards,
Aravindhan Krishnan...



On Mon, 7 Jun 2021 at 21:26, Aravindhan Krishnan <aravindhank11 at gmail.com>
wrote:

> Hi Folks,
>
> I am finding anomalous behavior when I am trying to run dhclient process
> inside my docker container in vanilla Ubuntu 16.04 host. The service gets
> into "deactivating" state and is stuck forever. In the mail I have attached
> a minimalistic reproduction of the issue seen.
>
> Working logic:
>
>    - There is a sample trial at .service script which invokes the `trial`
>    binary with the option passed to the systemd service via @ option
>    - The valid options are sleep and dhclient_<interface_name>
>    - The binary either invokes a long-lived sleep process or dhclient
>    process on the said interface_name based on the input
>    - The binary then spawns `kill_trial.sh` script. The script sleeps for
>    20 seconds and kills the parent `trial` binary. The kill signal is SIGKILL
>    in the trial example. In the real-world, this can be a SIGSEGV indicating a
>    crash in the parent process.
>    - If the trial binary was started for sleep process things work fine
>    and service goes into "failed" state as expected
>    - However, in case of dhclient, the service is stuck in "deactivating"
>    state if the underlying host OS is Ubuntu 16.04. This works well if the
>    host is running Ubuntu 20.04.
>    - We have kept TimeoutStopSec to infinity, because in real-word
>    deployments, the core collection post a crash takes varying time depending
>    on the memory config on the host.
>
>
> Steps to reproduce
> # tar -xf minimal_repro.tar -C minimal_repro/
> # cd minimal_repro/
> # docker build -t trial .
> # docker rm -f trial
> # docker run -it -d --net=host --privileged -v
> /sys/fs/cgroup:/sys/fs/cgroup:ro --name trial trial
> # docker exec -it trial bash
>
> # systemctl start trial at dhclient_eth1.service
>
> # #Keep monitoring trial at dhclient_eth1.service -- issue should be seen
> within 20-30 seconds on Ubuntu 16.04 host
>
> # systemctl status trial at dhclient_eth1.service
> ● trial at dhclient_eth1.service - Trial
>      Loaded: loaded (/etc/systemd/system/trial at .service; static; vendor
> preset: enabled)
>      Active: deactivating (stop-sigterm) (Result: signal) since Mon
> 2021-06-07 13:19:12 UTC; 1min 11s ago
>     Process: 55 ExecStartPre=/bin/bash
> /etc/systemd/system/trial_service_script.sh pre_start dhclient_eth1
> (code=exited, status=0/SUCCESS)
>     Process: 56 ExecStart=/bin/bash
> /etc/systemd/system/trial_service_script.sh start dhclient_eth1
> (code=killed, signal=KILL)
>    Main PID: 56 (code=killed, signal=KILL)
>       Tasks: 0 (limit: 38590)
>      Memory: 588.0K
>      CGroup:
> /docker/903fca0cee1387b7c2113a36ee5efdb3a25edd1e60584fe5da5d0c5b5ffd8241/system.slice/system-trial.slice/trial at dhclient_eth1.service
>
> # #NOTE: `Active: deactivating` -- in stuck state
> # #Running `systemctl daemon-reload` forces the service to go to failed
> state
>
> # systemctl start trial at sleep.service
>
> # #Keep monitoring trial at sleep.service -- would be killed in 20-30
> seconds and goes into failed state as expected
>
> # # systemctl status trial at sleep.service
> ● trial at sleep.service - Trial
>      Loaded: loaded (/etc/systemd/system/trial at .service; static; vendor
> preset: enabled)
>      Active: failed (Result: signal) since Mon 2021-06-07 13:38:19 UTC;
> 21s ago
>     Process: 113 ExecStartPre=/bin/bash
> /etc/systemd/system/trial_service_script.sh pre_start sleep (code=exited,
> status=0/SUCCESS)
>     Process: 114 ExecStart=/bin/bash
> /etc/systemd/system/trial_service_script.sh start sleep (code=killed,
> signal=KILL)
>     Process: 129 ExecStopPost=/bin/bash
> /etc/systemd/system/trial_service_script.sh post_stop sleep (code=exited,
> status=0/SUCCESS)
>    Main PID: 114 (code=killed, signal=KILL)
>
> Please advise on what can help us in alleviating the issue.
>
> Thanks,
> Aravindhan
>
> Regards,
> Aravindhan Krishnan...
>
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