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I have a local website on Debian 11 which is rarely used so I thought I might want to start Apache using systemd socket activation when visiting the site and then shut down after few minutes of inactivity.

After installing apache on debian I stop and disable the service with systemctl disable --now apache2.service, then create /etc/systemd/system/apache2.socket with the following content, reload systemd with systemctl daemon-reload, and start the socket with systemctl start systemd.socket.

[Unit] Description=Apache Server Socket [Socket] ListenStream=80 [Install] WantedBy=sockets.target

I can confirm systemd is actually listening, and apache is started when visiting the site, but it stops immediately with error

apachectl[2794]: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:80 apachectl[2794]: (98)Address already in use: AH00072: make_sock: could not bind to address 0.0.0.0:80

According to this answer it should work.

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  • Actually, according to the linked answer it does not work. Read the comment as well. Commented Jan 31, 2023 at 12:12
  • @GeraldSchneider though the comment to the first answer mentions this function github.com/apache/httpd/blob/… which uses freedesktop.org/software/systemd/man/sd_listen_fds.html as recommended for socket activation. Commented Jan 31, 2023 at 12:18
  • This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.. It's highly probable this code never ended up in Apache httpd. Commented Jan 31, 2023 at 12:21
  • Just configure Apache to spawn a single process and some more when needed and be done with it. Commented Jan 31, 2023 at 12:22
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    From my understanding of the linked answer this should be available in httpd 2.5. Commented Jan 31, 2023 at 12:24

1 Answer 1

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You can use systemd socket activation with Apache 2.4. The Fedora package has this configuration available by default; you just need to systemctl enable httpd.socket instead of systemctl enable httpd.service.

This example is from Fedora 37, which includes Apache 2.4.55.

The socket file look like:

[Unit] Description=Apache httpd Server Socket Documentation=man:httpd.socket(8) [Socket] ListenStream=80 NoDelay=true DeferAcceptSec=30 [Install] WantedBy=sockets.target

And the service unit is just the standard httpd.service:

[Unit] Description=The Apache HTTP Server Wants=httpd-init.service After=network.target remote-fs.target nss-lookup.target httpd-init.service Documentation=man:httpd.service(8) [Service] Type=notify Environment=LANG=C ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND ExecReload=/usr/sbin/httpd $OPTIONS -k graceful # Send SIGWINCH for graceful stop KillSignal=SIGWINCH KillMode=mixed PrivateTmp=true OOMPolicy=continue [Install] WantedBy=multi-user.target

With this in place, when I activate the socket (systemctl start httpd.socket) there are no httpd processes running:

# ps -fe |grep httpd root 1303 944 0 15:11 pts/0 00:00:00 grep --color=auto httpd #

But systemd is listening on port 80:

# ss -tlnp | grep :80 LISTEN 0 4096 *:80 *:* users:(("systemd",pid=1,fd=52))

If I connect to the socket:

# curl localhost

I can see that Apache is now handling connections:

[root@localhost system]# ps -fe | grep httpd root 1309 1 0 15:12 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND apache 1310 1309 0 15:12 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND apache 1311 1309 0 15:12 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND apache 1312 1309 0 15:12 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND apache 1313 1309 0 15:12 ? 00:00:00 /usr/sbin/httpd -DFOREGROUND root 1494 944 0 15:13 pts/0 00:00:00 grep --color=auto httpd
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  • Well I replaced the unit using systemctl edit --full apache2.service with this version, changing /usr/sbin/httpd to /usr/sbin/apache2. I fixed all configuration using variables in /etc/apache2/envvars, and started the socket. I'm still getting "address already in use" though. Commented Jan 31, 2023 at 18:25
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    It sounds like you're using Ubuntu. I took a look at the Ubuntu apache2 package, and it looks like it was built without HAVE_SYSTEMD defined, which means it doesn't have support for socket activation. This is an issue with how the package was built; Apache httpd itself does have the necessary support. Commented Feb 1, 2023 at 12:46

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