Date: Tue, 28 Jun 2005 11:10:23 GMT From: Bruce Evans <bde@zeta.org.au> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/82720: <[patch] Incorrect help output from growfs.c and mkfs.c> Message-ID: <200506281110.j5SBAMEB076580@freefall.freebsd.org>
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The following reply was made to PR bin/82720; it has been noted by GNATS.
From: Bruce Evans <bde@zeta.org.au>
To: "David D.W. Downey" <pgpkeys@pgpkeys.net>
Cc: freebsd-gnats-submit@FreeBSD.org
Subject: Re: bin/82720: <[patch] Incorrect help output from growfs.c and
mkfs.c>
Date: Tue, 28 Jun 2005 21:09:11 +1000 (EST)
On Tue, 28 Jun 2005, David D.W. Downey wrote:
> My rationale behind setting the Priority to serious is that if you do not
> know about fsck_ffs (which can be expected since the default and most known
> tool is fsck) then you will run into the issue of not knowing what to do to
> repair the broken system.
The bug was introduced when the old fsck was renamed to fsck_ffs and fsck
became a different program (a wrapper that selects a file-system-specific
fscks). This PR shows that the wrapper doesn't handle options very well.
> Case in point, I ran into this problem when a -CURRENT system was unable to
> repair the default superblock. It kept spitting out FREE BLOK COUNT(S) WRONG
> IN SUPERBLOCK. SALVAGE? [no]. Needless to say I spent probably 45 minutes
> digging through the man pages such as fsck, bread, sbread, sbwrite, several
> lib pages, et cetera trying to figure out how to find info about the next
> superblock in order to fix the situation.
It actually is described in fsck(8). The -T option can be used to pass
flags to file-system-specific fscks. This works like the -o option for
mount(8) except it is much more general despite less need for generality,
and thus is much harder to use: for mount, where you would say
mount -t <fstype1,...> -o <options>
and have all (?) options passed to the mount utility for each selected
fstype whether you want this or not, for fsck you can say
mount -T<fstype1>:<options for fstype1> -T<fstype2>:<opts2> ...
You can also say
fsck -t <fstype1,...>
but there is nothing corresponding to mount -o for fsck. (Note that
multiple fstypes are sometimes useful although not for fsck -b, erm
fsck_ffs -b, since they can be used to select a subset of all file
systems in /etc/fstab for mount -a and fsck <default>.)
> Now I'm just one person. Think of the affect on say just 5,000 people
> worldwide with this issue, finally finding newfs only to find out the
> information it gives is incorrect. Now add in the fact there's no mention of
> fsck_ffs which _is_ the right tool to fix the SB using the SB info spit out
> by newfs. There's no logical connection to the correct tool, leaving people
> stranded. Small item, this patch, but big help for administrative flow and
> repair.
I think the "right" tool is still fsck (with -T). However, this is
even harder to use than might first appear. Where for "mount -t" the
fstype to use is the actual kernel fstype whose mispelling for the
ffs file system is well known, the fstype for "fsck -T" is the one
in the disk label for the partition (if any (*)). "ffs" is misspelled
"ufs" in the kernel, so to mount(8) an ffs file system, you say
"mount -t ufs ...". (Similarly for other utilities that use
getvfsbyname(3), e.g., "find -t ufs".) For fsck, the the spelling of the
file system is normally (*) taken from the disk label, and the "ffs" is
usually mispelled "4.2BSD" there, so you have to say something like
"fsck -T4.2BSD:..." to run fsck on ffs file systems and pass options.
(fsck does some simple transformations of the typename, so you can also
say "fsck -T4.2bsd:...", but fsck doesn't have a dictionary of misspellings
so neither the "ffs" nor its usual misspelling are transformed to or from
"4.2BSD".) For passing the -b option, quoting is probably needed, so the
"right" way ends up as something like:
fsck -T4.2BSD:"-b 64"
Ugh. It's easier to describe and use the method in your patch.
(*) The fsck wrapper also fails if there is no disk label or other metadata
to give the fstype. In such cases, I don't know how to make it exec the
file-system-specific fsck so I just use the f-s-s fsck directly.
Anyway, perhaps your PR should be changed/enlarged to one about unclear
documentation in fsck.8.
Bruce
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