How to recover disk space after "filesystem full"

[Fred Condo]

On Fri, May 22, 2009 at 9:14 AM, Luke Dean <LukeD at pobox.com> wrote:
>
> Yes, it sounds like a stupid question, but let me tell the story.
>
> The log for my dhcp server filled up /var last night, which meant that
> dhcpd was also unable to hand out new leases, which meant that I had
> effectively been DOSed.  I'll have to look into changing my logging
> policies.
>
> So, to correct the problem, I log into the router, removed the big
> log and several other files in /var to free up some space, and assumed
> this would correct the problem.
>
> It did not.
> Several minutes after freeing up a lot of space on /var, I continued
> to get "filesystem full" messages and "df" continued to show the
> capacity at >100%.  I checked "df -i" for the inodes too.  That was
> fine.  I ran a quick fsck to see if that might shock the system into
> seeing all the space that I'd freed up, but no good.
>
> I ended up rebooting the box.
>
> Was there any other possible solution I could've tried?
>
> Why wouldn't the free space immediately appear as free?

Because unlinking the file does not close the file. Restarting the
dhcp daemon probably would have done the trick. The filesystem will
free the disk space only when all references to the file have gone
away.