Linux Dummy: Unscheduled Maintenance

If anyone of you have tried to access the blog yesterday night, you might have noticed that nothing was working. Sorry! I’ll say it straight, it’s completely my fault. Yesterday evening I decided to set up a cron job for automatic backups on my VPS – a full MySQL dump and a compressed archive of the www directory. So I got a couple of error messages stating that I don’t have the right to access some files which were in the wp-content/upload and wp-content/cache folders… I was frustrated!

Next… Never attempt to do this, okay? I logged in as root, changed owner on all files and folders including sub-folders of the www directory, set it to kovshenin:kovshenin. Voila, the backup worked! In a couple of minutes my VPS ran out of memory and I couldn’t even logon via SSH to reboot the server!

Now that’s funny! I called my hosting provider this morning and asked them what happened? They said everything’s fine, rebooted my server. I managed to logon by SSH, ran the “top” command, and looked at my memory usage growth! 100% was reached in 17 minutes, and bang! Disconnect. Two more calls to my provider didn’t help. They said that the only thing they can do is reset my yesterday’s VPS state completely.

So what really happened? I’m not sure but I bet it’s the WP-Super Cache plugin for WordPress! You see, cached files were created by the user that the httpd (apache) daemon ran – thus, one called “webmaster”. The user “kovshenin” apperantly didn’t have access to those files, and the change owner command spoiled all the cache! Now the static files were owned by “kovshenin”, and “webmaster” (apache) didn’t have any rights for those files. WP-Super Cache must have been in an infinite loop trying to access those, and of course, with no luck – therefore memory leak.

After another reboot I managed to quickly get into the WordPress control panel, enable Maintenance Mode and disable all the other plugins. Enabled them one by one. Setting 0777 as the rights for the cache directory and two WP-Super Cache config files solved the problem. The site was working fine again, and the new generated cache files were owned by “webmaster”… The day has been saved.

But what about the backups? Finally, I came to a thought that both “kovshenin” and “webmaster” users should be in the same groups. So I added “webmaster” to the “kovshenin” group, and “kovshenin” to the “webmaster”. Everything’s great! Apart from the fact that my Google Analytics now shows 0 visitors for 21.05.2009. Jeez, what a dummy…

About the author

Konstantin Kovshenin

WordPress Core Contributor, ex-Automattician, public speaker and consultant, enjoying life in Moscow. I blog about tech, WordPress and DevOps.