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From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.sys.next
Subject: Re: Lost 6 Megs of Hard Disk space
Message-ID: <1991Jun12.211009.16028@ni.umd.edu>
Date: 12 Jun 91 21:10:09 GMT
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fsck on the NeXT is just like fsck on any other [normal] BSD based
UNIX systems.  Its not so much the case of being in multi-user mode or
not, but if the file system is currently mounted.  You cannot use it
to fix a broken file system while it is mounted.

If you have a damaged file system, you should unmount it first (if its
not the root file system) and then run fsck on it.  After fsck has
repaired it, you can then manually remount it.  

There is no way to unmount the root file system, which is why you can
only repair it while in single user mode when you can easily halt the
system without syncing the in-memory state of the file system to the
disk.  If fsck has modified the root file system, then you *must* halt
the system **WITHOUT** syncing the file system.  For example,
/usr/etc/halt -n will do this.

Please remember, while you're running as root, you have the potential
to do a great deal of damage.  If you are not completely sure what a
command does, especially dangerous ones in /etc or /usr/etc, then you
shouldn't run them as root.  RTFM, or let the system "fix" itself if
it can when it reboots.

louie