Unable to start httpd service on Centos 7 "GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject"

Question

When trying to (re)start httpd service I get the following error:

** (pkttyagent:2574): WARNING **: 01:33:55.345: Unable to register authentication agent:
GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject Error registering authentication agent:
GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: Cannot determine user of subject (polkit-error-quark, 0) Job for httpd.service failed because the control process exited with error code. See "systemctl status httpd.service" and "journalctl -xe" for details.

Then

systemctl status httpd.service

sheds no light on the problem:

httpd.service - Web server Apache
   Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Wed 2020-07-22 01:33:55 BST; 26min ago
  Process: 2578 ExecStart=/usr/local/apache/bin/apachectl start (code=exited, status=1/FAILURE)

Jul 22 01:33:55 server... systemd[1]: Starting Web server Apache...
Jul 22 01:33:55 server... systemd[1]: httpd.service: control process exited, code=exited status=1
Jul 22 01:33:55 server... systemd[1]: Failed to start Web server Apache.
Jul 22 01:33:55 server... systemd[1]: Unit httpd.service entered failed state.
Jul 22 01:33:55 server... systemd[1]: httpd.service failed.

What might be causing this? Where should I look to debug?

Answer 1

[Thu Jul 23 05:40:44.885963 2020] [ssl:emerg] [pid 2877:tid 140514669713280] AH02565: Certificate and private key do not match

Looks like key and certificate do not match. Please check md5 of the key and cert file.

Answer 2

This usually happens when trying to restart a systemd service.

The workaround is as follows:

Run this as root

groupadd -g 23 nohidproc

usermod -a -G nohidproc polkitd

mount -o remount,rw,hidepid=2,gid=nohidproc /proc

systemctl restart polkit