Path: utzoo!attcan!uunet!husc6!mailrus!cwjcc!hal!nic.MR.NET!tank!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.unix.wizards
Subject: Re: disc labels on 4.3 (vax)
Keywords: disc label tahoe vax 4.3bsd
Message-ID: <14632@mimsy.UUCP>
Date: 18 Nov 88 23:18:27 GMT
References: <498@gould.doc.ic.ac.uk>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 24

In article <498@gould.doc.ic.ac.uk> aw@doc.ic.ac.uk (Andrew Weeks) writes:
>The question I want to ask is, will writing a label onto the disc affect
>the file system? i.e.  can I label a `live' disc, or should I only label
>a blank disc which I am then going to restore onto? 

You can label disks% that are in use, as long as the new label does not
move or resize partitions that are in use (the latter may or may not be
enforced by the kernel: it has changed on and off during development of
the labelling drivers).
-----
% For some reason, while a Frisbee is a `disc', a Winchester drive is a
`disk' :-)
-----

>The documentation we have doesn't say anything about this, which
>probably means it's safe, but then the label must take up some space,
>where can it get it except at the expense of files?

The label resides on sector zero, after (or in the middle of) the level
zero bootstrap code.  The label can be anywhere within sector 0, but is
normally at offset 64 (bytes).
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris