Today I was trying to install a PHP module but I kept getting "no space left" errors. This was interesting because my disks were not full in terms of both space and the number of inodes as evidenced by "df -k" and "df -i" commands. Then I found out that file system errors might be a cause for this. I didn't want to check mounted disks using fsck program so I used this page as a reference to easily check the file system on the next boot simply by creating a forcefsck file inside the root directory. After the file system check, I can confirm that the error went away.

I suppose file system checking should be one of the first things one should check in such a irregularity.