Replacing drive with root file system on

Matthew Seaman m.seaman at
Fri Oct 24 04:35:29 PDT 2003

On Fri, Oct 24, 2003 at 10:47:45PM +1300, Richard Shea wrote:
> Hi - I have a system with two IDE drives on it and I need more disk space
> than I have . The current situation is :
> Filesystem  1K-blocks    Used  Avail Capacity  Mounted on
> /dev/ad0s1a    257998   36308 201052    15%    /
> /dev/ad0s1f    498398  424568  33960    93%    /usr
> /dev/ad3s1e   7939980 6610848 693934    91%    /usr/home
> /dev/ad0s1e    226734    2542 206054     1%    /var
> procfs              4       4      0   100%    /proc
> I would like to swop the 1Gb ad0 drive for a larger drive. As you can see
> the other IDE drive is almost full. Can anyone suggest how to move what's
> on ad0 to a larger disk ? I wondered about 
> 1. disconnecting the ad3 and putting a new drive in its place
> 2. then (in some way) backuping up the entirety of ad0, restoring it to
> the 'fake' ad3 3. then taking out the original ad0 and replacing with ad3
> 4. then (in some way) persuading machine to boot off new, larget drive,
> with root on it 
> ... would that work  ? Can anyone fill in the details ? It it wouldn't
> work can anyone suggset an alternative bearing in in mind I can only have
> two drives and the largest each can be is 8Gb (old BIOS). 

You have pretty much the right idea.  I'd do the job something like

    i) Edit your /etc/fstab and comment out the line that mounts

   ii) Shutdown and remove the current ad3 drive. Add your new 8Gb
       disk in it's place.

  iii) Reboot to single user mode, mounting all of the partition from
       ad0, much as you would for doing a {build,install}world cycle:

        # fsck -p
        # swapon -a
        # mount -a

   iv) Set up the fdisk(8) slice table on your new drive: presumably
       you want the whole disk to be devoted to FreeBSD.  This also
       sets up the boot sector so that you can eventually boot from
       the disk.

        # fdisk -B -b /boot/mbr -I ad3

       Once you're done, modulo the exact size/cylinders/heads/sectors
       of the disk you should see output something like this:

        # fdisk ad3
        ******* Working on device /dev/ad3 *******
        parameters extracted from in-core disklabel are:
        cylinders=4462 heads=255 sectors/track=63 (16065 blks/cyl)
        Figures below won't work with BIOS for partitions not in cyl 1
        parameters to be used for BIOS calculations are:
        cylinders=4462 heads=255 sectors/track=63 (16065 blks/cyl)
        Media sector size is 512
        Warning: BIOS sector numbering starts with sector 1
        Information from DOS bootblock is:
        The data for partition 1 is:
        sysid 165,(FreeBSD/NetBSD/386BSD)
            start 63, size 71681967 (35000 Meg), flag 80 (active)
                beg: cyl 0/ head 1/ sector 1;
                end: cyl 1023/ head 254/ sector 63
        The data for partition 2 is:
        The data for partition 3 is:
        The data for partition 4 is:

    v) Set up FreeBSD partitions on your new drive using disklabel(8)
       -- decide before hand what partitions and what sizes you want:

        # disklabel -e ad3s1

       This will pop you into an editor -- you need to add lines at
       the end after where it says '8 partitions:' -- don't touch the
       line for c:, but add lines for a: (/), b: (swap), e: (/usr), f:
       (/var) etc. Set fstype to 4.2BSD (or swap for the swap
       partition).  Some calculation will be necessary here. Sizes are
       given in numbers of sectors, which are usually 512bytes apiece.
       Eventually you should end up with something that looks rather
       like this:

        #        size   offset    fstype   [fsize bsize bps/cpg]
          a:   262144        0    4.2BSD     1024  8192    16   # (Cyl.    0 - 16*)
          b:  2097152   262144      swap                        # (Cyl.   16*- 146*)
          c: 71681967        0    unused        0     0         # (Cyl.    0 - 4461*)
          e:   262144  2359296    4.2BSD     1024  8192    16   # (Cyl.  146*- 163*)
          f: 12582912  2621440    4.2BSD     1024  8192    16   # (Cyl.  163*- 946*)
          g: 56477615 15204352    4.2BSD     1024  8192    16   # (Cyl.  946*- 4461*)

       You need to fill in the first three columns -- you can fill in
       the fsize, bsize and bps/cpg fields if you want, but the
       newfs(8) command used in the next step will fill in the blanks
       for you.  The stuff after the '#' on each line is automatically

   vi) Create filesystems on the new partitions using newfs(8).  There
       are any number of parameters to play with when creating
       filesystems which is all very confusing.  If you don't have a
       specific need for a specially laid out FS, then just take the
       defaults.  These will be fine for general purpose filesystems
       of the sort of size you'll be needing:

        # newfs -v /dev/ad3s1a

       and the same for the other partitions ad3s1e, ad3s1f.  You
       don't need to do anything special to prepare the swap (b)

       If you want to use soft updates (definitely recommended for
       /usr and /var and usually good for / unless space is
       particularly tight) then you can enable it on the new
       partitions by

        # tunefs -n enable /dev/ad3s1a

      and analogously for the other filesystems.

  vii) Now mount the new partitions under /mnt:

        # mount -t ufs -o rw /dev/ad3s1a /mnt
        # mount -t ufs -o rw /dev/ad3s1e /mnt/usr
        # mount -t ufs -o rw /dev/ad3s1f /mnt/var

 viii) Use dump(8)/restore(8) to duplicate your original filesystems
       onto the new disk

        # dump -0 -f - / | ( cd /mnt ; restore rf - )
        # dump -0 -f - /usr | ( cd /mnt/usr ; restore rf - )
        # dump -0 -f - /var | ( cd /mnt/var ; restore rf - )

   ix) Unmount your new partitions, shutdown the machine and move your
       new disk to replace your original boot disk.  Stick your
       original /usr/home drive back in since you have the case open.

    x) Reboot to single user mode again.  The system should come up
       smoothly from the new disk.  If not, you'll have to open the
       case again, swap the old root disk back into the machine as ad0
       and the new disk back to ad3 and you should be able to get the
       system back up and try and fix things.

       When you get to single user, do the usual fsck and mount

        # fsck -p
        # swapon -a
        # mount -a

       Now edit the /etc/fstab file to uncomment the /usr/home line.
       Then fsck and mount that partition:

        # fsck -p /dev/ad3s1e
        # mount /usr/home

   ix) If everything has gone well so far, type Ctrl-D to exit from
       single user mode and continue booting up to full multi-user
       mode.  If not, you'll have to backtrack, work out what went
       wrong and fix it.

    x) That's it.  You're done.



Dr Matthew J Seaman MA, D.Phil.                       26 The Paddocks
                                                      Savill Way
PGP:         Marlow
Tel: +44 1628 476614                                  Bucks., SL7 1TH UK
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