Knowledge Base

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 :

PLESK_ERROR: 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.

Apache does not start via Plesk > Tools & Settings > Services Management or via SSH:

PLESK_ERROR: Unable to start service: Unable to manage service by apache_control_adapter: (‘start’, ‘web’). Error: INFO: [Wed Apr 14 09:50:54 EEST 2021]: Service: apache, Action: start Trying to start service httpd… attempt to start service httpd – service doesn’t exist (missing unit file or not executable control script) ***** problem report ***** Warning: start service httpd failed /usr/local/psa/admin/sbin/pleskrc execution failed: Unit httpd.service could not be found.

# systemctl start httpd
Failed to restart httpd.service: Unit not found.
Apache syntax has no errors:

# httpd -t
Syntax OK

Verification of Apache packages shows that the symlink to httpd.service was modified:

# yum list installed | grep httpd
httpd.x86_64 2.4.6-93.el7.centos @base
httpd-tools.x86_64 2.4.6-93.el7.centos @base

# rpm -V httpd.x86_64
…….T. c /etc/httpd/conf.modules.d/00-base.conf
…….T. c /etc/httpd/conf.modules.d/00-dav.conf
S.5….T. c /etc/httpd/conf.modules.d/00-mpm.conf
…….T. c /etc/httpd/conf.modules.d/00-proxy.conf
S.5….T. c /etc/httpd/conf/httpd.conf
S.5….T. c /etc/logrotate.d/httpd
….L…. /usr/lib/systemd/system/httpd.service
S.5….T. /usr/lib64/httpd/modules/mod_proxy.so
S.5….T. /usr/lib64/httpd/modules/mod_proxy_fcgi.so
SM5….TP /usr/sbin/suexec

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

Log in to Plesk.
Remove the Litespeed extension via Extension Catalog > My Extensions > LiteSpeed > More > Remove.
Connect to the server via SSH.
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
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*

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…