Re: how to boot or access problem file system
- From: PJ <af.gourmet@xxxxxxxxxxxx>
- Date: Fri, 31 Jul 2009 16:10:39 -0400
Roland Smith wrote:
On Fri, Jul 31, 2009 at 03:12:21PM -0400, PJ wrote:
Roland Smith wrote:
On Thu, Jul 30, 2009 at 03:20:55PM -0400, PJ wrote:I get the impression that my disks have all been overwritten; it's
Roland Smith wrote:I forgot to mention that your boot sector is fine. If it were screwed
On Thu, Jul 30, 2009 at 01:40:58PM -0400, PJ wrote:
What can be done to access a file system that seems to have the boot
sector screwed up?
up, you wouldn't get to the boot prompt.
Since the boot code cannot locate your kernel, there are several things
that could have gone wrong. See below.
<snip>
Use a livefs cd or use the Fixit option in the main menu of sysinstallhow can I use it if I can't boot or access the file system?The /usr files should be ok but how to access?Use fsck_ffs to try and repair the filesystem.
on an install disk. That should get you a shell where you can run
fsck_ffs on your disk partitions.
If you have booted from CD, list the disk devices with e.g. 'ls
/dev/ad*'. If you have SCSI drives, use 'da' instead of 'ad'.
What does that command list? On my machine, I'll get
something like this:
/dev/ad4 /dev/ad4s1d /dev/ad6 /dev/ad6s1d
/dev/ad4s1 /dev/ad4s1e /dev/ad6s1 /dev/ad6s1e
/dev/ad4s1a /dev/ad4s1f /dev/ad6s1a /dev/ad6s1f
/dev/ad4s1b /dev/ad4s1g /dev/ad6s1b /dev/ad6s1g
/dev/ad4s1c /dev/ad4s1g.eli /dev/ad6s1c /dev/ad6s1g.eli
If you only see e.g. /dev/ad4 and /dev/ad6, your slice table has been
overwritten (with fdisk) and your data is lost. If you see /dev/ad4s1
but not /dev/ad4s1a-g, the BSD partitions have been removed and your
data is lost as well.
Since there is only one slice on both ad4 and ad6 (otherwise you'd see
/dev/ad4s2x) The next step is to examine the disk labels:
bsdlabel /dev/ad4s1
# /dev/ad4s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 1024000 16 4.2BSD 2048 16384 64008
b: 16777216 1024016 swap
c: 976768002 0 unused 0 0 # "raw" part, don't edit
d: 4194304 17801232 4.2BSD 2048 16384 28528
e: 104857600 21995536 4.2BSD 2048 16384 28528
f: 41943040 126853136 4.2BSD 2048 16384 28528
g: 807971826 168796176 4.2BSD 2048 16384 0
This tells us that the a, d, e, f and g partition are carrying a BSD
filesystem, and should be checked with fsck_ffs.
Try these steps and report back what you find.
It is a mailing list for questions. Ipso facto you'll see questions andMaybe the real problem is that the manual is too screwed up (why areI don't have a problem with irrecoverable files, I would just finallyMake regular backups. Especially before big upgrades.
understand how things work and what can be done on FBSD.
there so many problems being brought up on the mailing lists? we can't
all be that stupid.)
problems on this list. People who are not having problems will not be
posting very much. :-)
As to the handbook, this is by necessity written by people who are
knowledgeable on the subject they write on. Unfortunately this sometimes
lead to really basic steps/assumptions being skipped because they are
self-evident for the writer. If you gain enough knowledge about a
subject it becomes really hard to write for people new to the system
because you've internalized a lot of stuff by then.
If you have specific questions about parts of the handbook, ask.
Don't have impressions. Get the data. Boot from a livefs CD and start a
shell as explained in in some of my previous messages. Then use the commands
listed above to check your filesystems. *And report back wat you found*.
rather strange that in the instructions to upgrade it says to not change
anything on the Newfs... and that files would not be overwritten... is
that at fact?
What instructions are you referring to? Neither the handbook section
[http://www.freebsd.org/doc/en/books/handbook/updating-freebsdupdate.html]
nor the manual page for freebsd-update mention newfs at all! Nor should they.
Well, it sounds like we should be ok, but the instructions I am speaking
of are those on the installation disks ... when one selects the update
to a newer version and then as asked to set the slice names /; swap;
/tmp; and /var.
If I have made an error in this, then I can only put the full blame on
whoever created the installation system... there should be the most
obvious checks & balances about such an installation/upgrade as -
warnings about what the installation is going to do, and are you sure
this is what you want to do; and warnings that any existing files will
be overwritten... I have always cringed a bit when installing as there
were never any decent confirmations as to what was happening... even
Microsoft is pretty good with warning.
So, as I mentioned, I cannot access any disks as "Permission denied"
This seems to be a dead end. :-(
If that is true, then surely it should be possible to recover files in
the /usr /var and /tmp directories. If the disks have not been
overwritten... I think there was a huge misinformation gap here if this
is not so...
For an upgrade, the filesystems are not overwritten. Only a new install
creates new filesystems.
Please boot from a livefs CD and check the filesystems on the harddisk
as explained before and report the results.
Roland
--
Hervé Kempf: "Pour sauver la planète, sortez du capitalisme."
-------------------------------------------------------------
Phil Jourdan --- pj@xxxxxxxxxxxxx
http://www.ptahhotep.com
http://www.chiccantine.com/andypantry.php
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