[Bug 2037399] [NEW] Processes keep running after "systemctl stop"

[Mario Emmenlauer]

Public bug reported:

I have a number of Ubuntu 22.04 installations on various computers. In
the last month, I have seen more and more log messages like the
following from different systems:

```
systemd[1]: apache2.service: Unit process 70257 (apache2) remains running after unit stopped.

systemd[1]: exim4.service: Unit process 61890 (exim4) remains running after unit stopped.
```

I started considering this a problem when subsequently, some php
processes continued running after `systemctl stop apache2.service`. This
can be a problem when rogue processes interfere with my file-based
backup. I had at least one case where a rogue `php` process started
misbehaving after both `apache2` and `mysql` where stopped. The `php`
processes continued running, possibly inside a rogue `apache2` process,
but failed to continue its normal operation due to the absence of
`mysql`.

Motivation: I have a nightly backup script that stops common services
like `exim4`, `apache2` and `mysql`, then performs file-based backup,
and subsequently starts services again. I was relying on the fact that
processes would end after `systemctl stop`, and do not modify the file
system anymore. But this seems not always to be the case?

I do not necessarily think that this is a duplicate of
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2013543. The way
I understand the other bug is that systemd forgets about running
processes. Here in my case, systemd seems well aware that not all
processes ended, at least this is what the log message indicates. But
systemd does not force them to quit.

Expected behavior: After `systemctl stop`, I would need all processes to
end. This would be required so that I can be sure that it is safe to
perform file based backup, without modifications on the file system.

** Affects: systemd (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2037399

Title:
  Processes keep running after "systemctl stop"

Status in systemd package in Ubuntu:
  New

Bug description:
  I have a number of Ubuntu 22.04 installations on various computers. In
  the last month, I have seen more and more log messages like the
  following from different systems:

  ```
  systemd[1]: apache2.service: Unit process 70257 (apache2) remains running after unit stopped.

  systemd[1]: exim4.service: Unit process 61890 (exim4) remains running after unit stopped.
  ```

  I started considering this a problem when subsequently, some php
  processes continued running after `systemctl stop apache2.service`.
  This can be a problem when rogue processes interfere with my file-
  based backup. I had at least one case where a rogue `php` process
  started misbehaving after both `apache2` and `mysql` where stopped.
  The `php` processes continued running, possibly inside a rogue
  `apache2` process, but failed to continue its normal operation due to
  the absence of `mysql`.

  Motivation: I have a nightly backup script that stops common services
  like `exim4`, `apache2` and `mysql`, then performs file-based backup,
  and subsequently starts services again. I was relying on the fact that
  processes would end after `systemctl stop`, and do not modify the file
  system anymore. But this seems not always to be the case?

  I do not necessarily think that this is a duplicate of
  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/2013543. The
  way I understand the other bug is that systemd forgets about running
  processes. Here in my case, systemd seems well aware that not all
  processes ended, at least this is what the log message indicates. But
  systemd does not force them to quit.

  Expected behavior: After `systemctl stop`, I would need all processes
  to end. This would be required so that I can be sure that it is safe
  to perform file based backup, without modifications on the file
  system.

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