how to boot or access problem file system

Fri Jul 31 18:36:26 UTC 2009

Roland Smith wrote:
> On Thu, Jul 30, 2009 at 03:20:55PM -0400, PJ wrote:
>   
>> Roland Smith wrote:
>>     
>>> 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?
>>>>         
>
> I forgot to mention that your boot sector is fine. If it were screwed
> 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>
>   
>>>> The /usr files should be ok but how to access?   
>>>>         
>>> Use fsck_ffs to try and repair the filesystem.
>>>   
>>>       
>> how can I use it if I can't boot or access the file system?
>>     
>
> Use a livefs cd or use the Fixit option in the main menu of sysinstall
> 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.
>
>   
>>>> I don't have a problem with irrecoverable files, I would just finally
>>>> understand how things work and what can be done on FBSD.
>>>>         
>>> Make regular backups. Especially before big upgrades.
>>>   
>>>       
>> Maybe the real problem is that the manual is too screwed up (why are
>> there so many problems being brought up on the mailing lists? we can't
>> all be that stupid.)
>>     
>
> It is a mailing list for questions. Ipso facto you'll see questions and
> 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.
>
>
> Roland
>   
Thanks for replying Roland,
I've been struggling with upgrading 7.0 to 7.2... it has taken a lot of
my time and I am still not happy.
I have it running now; Xorg finally came through but I have absolutely
no idea how or why it finally started working. Actually, it was my last
attempt to start it and I was totally surprised that it came up. I
decided to try my former xorg.conf file which had the correct mouse
driver etc. that hal did not find. X -configure was useless and totally
off the track and tweaking the xorg.conf.new file did not work. In total
desperation I had installed all the xorg files needed or not and hoped
that might help... at first, it did not, at least I couldn't tell as
there was no change. But getting flashplayer to work... that's an
impossibility as I can see on this machine. Nor does gnash work... it
installs and shows up under about:plugins on Firefox... but that's as
far as it goest... same for flashplayer9 and linux-f8-flashplayer10
can't find the files to download ( but a few days ago they were
available and worked on the amd64 system).
Anyway... back to the messed up 7.1 installation.
I ran livefs 7.1 and chose option 6 (I think; it was the last on the
list) and I got the boot cursor (I think) ... so I entered? and got the
list of commands. BTW, I don't know where to find some instructions on
how to use the livefs and the command line procedures to work with to do
a reccovery. For one, I find that the screen scrolls by so fast, I miss
half of what is going on and I don't know how to get more to work... it
never has before...

I finally got a list of the devices with lsdev and thatgives me
cd devices:
  cd0: Device 0x1
disk devices:
  disk0: BIOS drive a:
  disk1: BIOS drive C:
    disk1s1: Unknown fs: 0x7 (I think this must be ntfs ? but ? )
  disk2: BIOS drive D:
  disk3: BIOS drive E:
    disk3s1a: FFS
    disk3s1b: swap
    disk3s1d: FFS
    disk3s1e: FFS
    disk3s1f: FFS
pxe devices:
======
ls shows what apears to be the filesystem: a couple of files and 
directories ======
using more to read files, I found that the file system does not appear
to be what  I had... for example, rc.conf doesn't exist; which leads me
to believe that what I am looking at is some default stuff for setup

How can I see all the commands?  They scroll by too fast. What's the use
of having such help when you can't see the output? This has always been
a deterrent for me to try to delve deeper into FBSD... doesn't anyone in
FreeBSD-land ever think about the enduser? I, for one, expect things to
be intuitive if not logical and I just don't find it here of in the
manuals...which, BTW, show up through Google in different forms and
configurations.

How do I see the contents of the other disks as I seem to be looking at
disk3? Is it possible to switch to another disk and see what is there?

-- 
Hervé Kempf: "Pour sauver la planète, sortez du capitalisme."
-------------------------------------------------------------
Phil Jourdan --- pj at ptahhotep.com
   http://www.ptahhotep.com
   http://www.chiccantine.com/andypantry.php