Now let's compare restart behavior with systemctl and apache2ctl. Again,
with questing, same as comment above.
a) systemctl
Restart really stops everything, and starts it again.
Looking at stop + start as defined in the systemd unit, a restart invokes:
apachectl graceful-stop --> apache2 -k graceful-stop
apachectl start
This is what we want in a package upgrade, generally: graceful-stop will
not abort open connections.
PIDs all change (no connection open in this example):
root@q-apachectl:~# pidof apache2
3468 3467 2980
root@q-apachectl:~# systemctl restart apache2
root@q-apachectl:~# pidof apache2
4320 4319 4317
Apache receives SIGWUNCH:
[Fri Mar 27 17:54:02.072749 2026] [mpm_event:notice] [pid 2980:tid 2980]
AH00492: caught SIGWINCH, shutting down gracefully
systemd is tracking the correct processes as expected:
root@q-apachectl:~# systemctl status apache2
● apache2.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/apache2.service; enabled; preset:
enabled)
Active: active (running) since Fri 2026-03-27 17:54:02 UTC; 16s ago
Invocation: 5e1fbc43f9784b3bb76295aa3975c749
Docs: https://httpd.apache.org/docs/2.4/
Process: 4314 ExecStart=/usr/sbin/apachectl start (code=exited,
status=0/SUCCESS)
Main PID: 4317 (apache2)
Tasks: 55 (limit: 9242)
Memory: 4.9M (peak: 5.7M)
CPU: 41ms
CGroup: /system.slice/apache2.service
├─4317 /usr/sbin/apache2 -k start
├─4319 /usr/sbin/apache2 -k start
└─4320 /usr/sbin/apache2 -k start
b) apache2ctl restart
Here restart sends a SIGHUP, and the parent process remains.
root@q-apachectl:~# pidof apache2
4320 4319 4317
root@q-apachectl:~# apache2ctl graceful
graceful graceful-stop
root@q-apachectl:~# apache2ctl restart
root@q-apachectl:~# pidof apache2
4530 4529 4317
root@q-apachectl:~# systemctl status apache2
● apache2.service - The Apache HTTP Server
Loaded: loaded (/usr/lib/systemd/system/apache2.service; enabled; preset:
enabled)
Active: active (running) since Fri 2026-03-27 17:54:02 UTC; 5min ago
Invocation: 5e1fbc43f9784b3bb76295aa3975c749
Docs: https://httpd.apache.org/docs/2.4/
Process: 4314 ExecStart=/usr/sbin/apachectl start (code=exited,
status=0/SUCCESS)
Main PID: 4317 (apache2)
Tasks: 55 (limit: 9242)
Memory: 4.9M (peak: 5.7M)
CPU: 97ms
CGroup: /system.slice/apache2.service
├─4317 /usr/sbin/apache2 -k start
├─4529 /usr/sbin/apache2 -k start
└─4530 /usr/sbin/apache2 -k start
[Fri Mar 27 17:58:35.745458 2026] [mpm_event:notice] [pid 4317:tid 4317]
AH00494: SIGHUP received. Attempting to restart
This will abort current open connections, differently from graceful
(which sends SIGUSR1).
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https://bugs.launchpad.net/bugs/1832182
Title:
systemd unable to detect running apache if invoked via "apache2ctl
graceful"
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