Today apache was stuck with the below error and it was not starting at all.
Sep 15 06:18:24 server.example.com systemd[1]: Starting The Apache HTTP Server... Sep 15 06:18:24 server.example.com httpd[15037]: [Thu Sep 15 06:18:24.591424 2016] [so:warn] [pid 15037] AH01574: module ruid2_module is alread...skipping Sep 15 06:18:33 server.example.com systemd[1]: httpd.service: main process exited, code=exited, status=1/FAILURE Sep 15 06:18:33 server.example.com kill[15038]: kill: cannot find process "" Sep 15 06:18:33 server.example.com systemd[1]: httpd.service: control process exited, code=exited status=1 Sep 15 06:18:33 server.example.com systemd[1]: Failed to start The Apache HTTP Server. Sep 15 06:18:33 server.example.com systemd[1]: Unit httpd.service entered failed state. Sep 15 06:18:33 server.example.com systemd[1]: httpd.service failed. Hint: Some lines were ellipsized, use -l to show in full.
It turned to be an semaphore issue.
Solution
RHEL CentOS 5/6
- add the below to /etc/sysctl.conf
kernel.msgmni = 1024 kernel.sem = 250 32000 100 512 kernel.shmmax = 16296951808 kernel.shmall = 17039360
- run
sysctl -p
RHEL CentOS 7
- add the below to /etc/sysctl.d/httpdfix.conf
kernel.msgmni = 1024 kernel.sem = 250 32000 100 512 kernel.shmmax = 16296951808 kernel.shmall = 17039360
- run
sysctl -p /etc/sysctl.d/httpdfix.conf
I was able to restart apache after this fix. 🙂
