the /debug partition
Archer Sully
archer at elysium.SGI.COM
Thu Jul 28 01:36:30 AEST 1988
In article <8807260558.AA07135 at uunet.UU.NET>, bernie at cidam.rmit.OZ.AU (Bernard Kirby) writes:
>
> We recently had one of our machines upgraded to a 4D-70GT running
> version 3 of the operating system (4sight 1.0 etc). After all the
> software was installed we noticed that a "df" showed an "extra"
> partition /dev/debug of type dbg mounted on /debug. It was about
> 50Mb in size! There appeared to be files in the /debug directory,
> but whenever you tried to look at them, nothing happened, like they
> were zero length files, except that "ls -l" showed that some of them
> were quite large in size. The number and size of files varied as the
> machine was used. This partition was not in /etc/fstab but was in
> /etc/mtab. So, one day in a fit of experimentality we simply "umount"ed
> it, and it hasn't reappeared since, even after a reboot.
> Now for the questions.
>
> a) Is this a "hidden" partition that is secretly present on all SGI
> machine's disks, only manifesting itself when explicitly mounted?
yes, it is present, because it is really the swap partition.
>
> b) Is it really about 50Mb in size, or is that simply a function of "df"
> misinterpreting a file system of type dbg.
>
> OR
>
> c) Did the Version 3 system repartition our disk without telling us?
> If it did, then it must have zapped some files.
>
It really is 50MB.
> d) Can we use it for something else, like an NFS partition?
>
no
> e) If we can't use it for anything else, can we reclaim the disk space?
> (If in fact is really is using disk space)
>
Since it doesn't use any space that wasn't already allocated, this
isn't a problem.
> f) What the F**k's it for? Why did it just show up unannounced, with no
> documentation about what it's doing.
>
/debug is used by debuggers and other programs that like to control
processes other than themselves. The idea is that when you access a
file in the /debug partition, the kernel actually performs an operation
on another process. This is what allows dbx to attach to a running
process.
If /debug won't remount, check your /etc/fstab. it should have this
line in it:
/debug /debug dbg rw 0 0
If it doesn't, put it back. If it does, make sure that the /debug
mount point is still there. If both conditions are true, then I
have no idea what you've done to your system. Try re-installing
3.0, or waiting for the maintenance release to get there.
There will be a man page for /debug in the next general software release.
> Thanks,
> Bernie Kirby.
You're Welcome,
Archer Sully
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