Re: Can't figure out what's taking up space on /

On Tue, Aug 03, 2021 at 10:03:44AM +0200, Paul de Weerd wrote:
> df shows you how much data you can write to an fs, while du shows the
> disk usage of files it can find. If it can't find a file (because
> it's been deleted), it won't account for it. But if it's been deleted
> and still held open by some process, it would still consume disk
> space.
>
> So it looks like a process has a file open on the root filesystem that
> has been deleted. You're looking for a root-owned process that is
> (probably) long-running. My guess the file is in /dev/ (that's my
> crystal ball talking though).
>
> Easiest way out is generally to reboot - this stops all processes
> (d0h), dus freeing up all the resources they had tied up, including
> files that had been deleted from the filesystem. But going through
> your process list to see if you can spot something that may have done
> this can be a good learning experience. In general, base OpenBSD
> daemons don't behave this way.

I agree with Paul: you should have a running process which hold
descriptor on unlinked file.

fstat(1) could be used to see list of opened files, and specially
unlinked files:

INUM The inode number of the file. It will be followed by an asterisk
('*') if the inode is unlinked from disk.


$ fstat | grep -F '* -'
[...]
semarie chrome 537 25 /tmp 48* -rw------- rwp 279793
[...]

here, chrome (pid 537) has descriptor 25 opened to a file on /tmp
inode=48 (unlinked), the file size is 279793 bytes.

--
Sebastien Marie