Unable to start Apache in Plesk: Failed to restart httpd.service: Unit not found

Symptoms

• Plesk runs on RHEL-based OS (CentOS/RHEL/CloudLinux).

• The following message appear on Plesk homepage or on attempt to start Apache at Tools & Settings > Services Management :

  Warning: start service httpd failed /usr/local/psa/admin/sbin/pleskrc execution failed: Failed to start httpd.service: Unit not found. Unit httpd.service could not be found.

• LiteSpeed was previously activated on the server but now it is disabled at Extension Catalog > My Extensions:
  

Cause

LiteSpeed was not fully deactivated. The file /usr/lib/systemd/system/httpd.service is a symlink to a non-existent LiteSpeed service /usr/lib/systemd/system/lshttpd.service:

# ls -lah /usr/lib/systemd/system/http*
lrwxrwxrwx 1 root root 39 /usr/lib/systemd/system/httpd.service -> /usr/lib/systemd/system/lshttpd.service

Resolution

1. Log in to Plesk.

2. Remove the Litespeed extension via Extension Catalog > My Extensions > LiteSpeed > More > Remove.

3. Connect to the server via SSH.

4. Find the old Apache and LiteSpeed .service files:

   # ls -lah /usr/lib/systemd/system/http*
   lrwxrwxrwx 1 root root 39 /usr/lib/systemd/system/httpd.service -> /usr/lib/systemd/system/lshttpd.service

   # ls -lah /usr/lib/systemd/system/lshttpd*
   lrwxrwxrwx 1 root root 39 /usr/lib/systemd/system/lshttpd.service

5. Remove the old httpd.service files and lshttpd.service files:

   # rm -rf /usr/lib/systemd/system/httpd.service*
   # rm -rf /usr/lib/systemd/system/lshttpd.service*

6. Create a new file /usr/lib/systemd/system/httpd.service and add the following content:

   # vi /usr/lib/systemd/system/httpd.service

   [Unit]
   Description=The Apache HTTP Server
   After=network.target remote-fs.target nss-lookup.target
   Documentation=man:httpd(8)
   Documentation=man:apachectl(8)
   [Service]
   Type=notify
   EnvironmentFile=/etc/sysconfig/httpd
   ExecStart=/usr/sbin/httpd $OPTIONS -DFOREGROUND
   ExecReload=/usr/sbin/httpd $OPTIONS -k graceful
   ExecStop=/bin/kill -WINCH ${MAINPID}
   # We want systemd to give httpd some time to finish gracefully, but still want
   # it to kill httpd after TimeoutStopSec if something went wrong during the
   # graceful stop. Normally, Systemd sends SIGTERM signal right after the
   # ExecStop, which would kill httpd. We are sending useless SIGCONT here to give
   # httpd time to finish.
   KillSignal=SIGCONT
   PrivateTmp=true
   [Install]
   WantedBy=multi-user.target

7. Start Apache service:

   # systemctl start httpd