Recently one our client called me and said Magento Site is not working so I checked the site and found following error.
So what's the meaning of this error. At first it looks like a permission issue that tmp folder does not have necessary permissions. I checked through SSH and permission was ok. But still it's not working.
Second issues could be tmp folder owner is not web root, hence it's not allowing to create files from web users. I checked that also and owner was correct.
After few checks through SSH, I found out that it was actually an issue of Inodes on server. Disk was almost full and there were no enough space to create new files. So have to delete some files to create space.
This you can do through SSH, but make sure you what are the files you are deleting and will that create any issues. If you don't know much about magento files and folders, PLEASE CONTACT YOUR HOSTING PROVIDER to delete it for you.
In my case I deleted old backups of database and deleted magento caches and sessions files from /var folder and then my site was up and working normally.
Hope this helps you.