Unable to restart PHP-FPM/Apache, /tmp read-only mode

Symptoms

Attempting to restart Apache or PHP-FPM produces errors such as:

# Apr 02 19:16:23 server restartsrv_httpd[24273]: Service Error
Apr 02 19:16:23 server restartsrv_httpd[24273]: 
(XID wg98e6) The “apache_php_fpm” service failed to restart because the… error:
Apr 02 19:16:23 server restartsrv_httpd[24273]: 
apache_php_fpm has failed. Contact your system administrator if the ser...over.
Apr 02 19:16:23 server restartsrv_httpd[24273]: 
restartsrv_apache_php_fpm --graceful exited unclean

Websites will show 500 errors, and the Apache error_log will show errors such as:

# Fri Apr 2 20:38:29 2021 (4546): Fatal Error Unable to create lock file: 
Bad file descriptor (9)
[Fri Apr 02 20:38:29.030721 2021] [cgid:error] [pid 4363:tid 47947418986240] 
[client 203.0.113.2:48980] End of script output before headers: ea-php56

Attempting to create files in /tmp fails with a "Read-only" error:

# touch /tmp/test
touch: cannot touch ‘/tmp/test’: Read-only file system

Cause 

When file system errors occur on the partition, the OS will mark the file system "read-only." This prevents services, such as Apache and PHP-FPM, from creating temporary files. 

Resolution

Note: The following procedure should be performed by a certified administrator to ensure nothing goes wrong.

1. Access the server's command line as the root user via SSH or Terminal in WHM.
2. Open /etc/fstab in your preferred text editor.

3. Comment out the /tmp entry by adding a # to the beginning of the line:

   CONFIG_TEXT: #/usr/tmpDSK      /tmp         ext3   defaults,noauto        0     0

4. Disable the securetmp service.

   # systemctl disable securetmp

5. Reboot the server.

   # shutdown -r now

6. Remove the old tmpDSK file.

   # /bin/rm /usr/tmpDSK

7. Run the securetmp script.

   # /scripts/securetmp

8. Enter Y at the prompts to confirm, enable, and configure the boot option.

9. Reboot the server again.

   # shutdown -r now