File system bafflement

[Robert Heller]

At Tue, 2 Sep 2014 20:30:57 +0100 "Ubuntu user technical support,  not for general discussions" <ubuntu-users at lists.ubuntu.com> wrote:

> 
> On Tue, 2 Sep 2014 14:09:59 -0400
> Robert Heller wrote:
> 
> > > So is rebooting a solution to this sort of problem?  
> > 
> > Yes.  Less drasticly, sending SIGHUP to syslogd will also work (assuming
> > it is specificly syslogd that is hanging onto the open file).  Basically,
> > doing the needful thing to whatever process is hanging onto the unlinked
> > file, whether that means sending it a signal to close its open files and
> > re-open new ones (which is what SIGHUP tells syslogd to do), or simply
> > killing off whatever wedged process that is doing this.  syslogd is just
> > a common deamon that causes this, esp. when a novice sys admin sees his
> > disk space vanishing and decides to something like
> > 'bzip2 /var/log/syslog' and then wonders why his disk space usage just
> > got *worse* and du ceases to be helpful or accurate (when compared to df).
> 
> OK. I rebooted, but df still says 100% use for root filesystem, and I get a
> window that says:-
> The volume "filesystem root" has only 0 bytes disk space remaining.
> 
> And this means that I can't do any security updates because the software
> updater doesn't think there's enough space.
> 
> It's starting to look like a complete re-install .....

No, not yet.  There is another possiblity: you have files 'hiding' under a 
mount point.  Reboot to single user mode (or boot with a live cd), and unmount 
all of the file systems except the root (/) file system.  Check to be sure 
that *every* mount point is in fact an *empty* directory.  If not, you have 
found your mising disk space.  Move or delete the files in question.  They are 
probably historical data, but you might want to back them up to external media 
before deleting them, just in case.

> 
> - Richard.

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