backups & cloning

[Polytropon]

On Tue, 29 Sep 2009 19:44:38 -0400, PJ <af.gourmet at videotron.ca> wrote:
> This may be clear to someone; it certainly is not to me.
> As I understand it, newfs will (re)format the slice.

No. The newfs program does create a new file system. In
other terminology, this can be called a formatting process.
Note that NOT a slice, but a PARTITION is subject to this
process. So

	# newfs -U /dev/ad2s1a

does format the first partition (a) of the first slice (s1)
of the third disk (ad2).



> Ok,  But what is standard out in the above example.  The dump is from
> where to where?

According to the command

	# dump -0Lauf - /dev/ad1s1a | restore -rf -

you need to understand that the main purpose of dump is to
dump unmounted (!) file systems to the system's tape drive.
Assuming nobody uses tape drives anymore, you need to specify
another file, which is the standard output in this case, which
may not be obvious, but it is if we reorder the command line:

	# dump -0 -L - a -u -f - /dev/ad1s1a | restore -r -f -

You can see that -f - specifies - to be the file to backup to.
The backup comes from /dev/ad1s1a.

The restore program, on the other side of the | pipe, does
usually read from the system's tape drive. But in this case,
it reads from standard input as the -f - command line option
indicates. It restores the data to where the working directory
at the moment is.

Here's an example (ad1 is source disk, ad2 is target disk):

	# newfs -U /dev/ad2s1a
        # mount /dev/ad2s1a /mnt
        # cd /mnt
        # dump -0Lauf - /dev/ad1s1a | restore -rf -



> Could someone clarify all this for me?

Hopefully hereby done. :-)



> So far, I have been unable to dump the / slice, not even with the -L
> option.

Always keep in mind: Use dump only on unmounted partitions.



> I am trying to dump the whole system (all the slices)except swap
> to a usb (sata2 500gb disk) and then restore to another computer with
> 7.2 minimal installation.

I think that's not possible because dump operates on file system
level, which means on partitions, not on slices.



> Slices ad2s1d,e,f and g dump ok to usb. a does not - errors ("should use
> -L when dumping live filesystems)

Keep an eye on terminology, you're swapping them here: The
devices ad2s1[defg] are partitions, not slices. The corresponding
slice that holds them is ad2s1.

Anyway, if you can, don't dump mounted file systems. Go into
single user mode, mount / as ro, and run dump + restore. If you
can, use a live system from CD, DVD or USB, which makes things
easier.



> Do you have to newfs each slice before restoring? 

Partitions. You don't have to newfs them once they are formatted.
It's just the usual way to ensure they are free of any data.



> But if you are
> restoring on a running 7.2 system, don't you have to restore to another
> disk than the one the system is on?

I don't understand this question right... if you're using a running
system for dump + restore - which is the system you want to be the
source system, then do it in minimal condition. SUM is the most
convenient way to do that, with all partitions unmounted, and
only / in read-only mode so you can access the dump and restore
binaries.



> I am beginning to think that you have to have a system running and dumpt
> to another disk on that system and then remove that disk and install in
> another box and boot from that?
> Am I getting close?

Again, I'm not sure I understood you correctly. If you've done
the dump + restore correctly, you always end up with a bootable
system, so you can boot it in another box. Dumping and restoring
just requires a running system, no matter if it is the source
system itself or a live system from CD, DVD or USB. (I prefer
tools like FreeSBIE for such tasks, but the FreeBSD live system
CD is fine, too.)

As far as I now understood, you don't want to clone from source
disk to target disk, but use a USB "transfer disk"; in this case,
you first need to clone onto this disk, and then use it in the
other computers to fill their disks with the copy you made from
your "master system".

As a sidenote, it's worth mentioning that this can be achieved
in an easier way: You create a minimal bootable FreeBSD on this
USB disk, in case your computers can boot from it; if not, use
a live system to boot the computers. Then, format the USB disk
with only one file system (e. g. /dev/da0) and put dump files
onto it, so they are available then as /mnt/root.dump, tmp.dump,
var.dump, usr.dump and home.dump. Instead of using -f - for the
dump and restore program, use those file names.



> I know it's a lot to ask, but then, I know you guys are capable...  :-)

If you still have questions, try to ask them as precise as
possible.

I may add that this list is the most friendly and intelligent
community to ask, so you're definitely at the right place here.



To illustrate a dump and restore process that involves several
partitions, just let me add this example:

Stage 1: Initialize slice and partitions
        # fdisk -I -B ad1
        # bsdlabel -w -B ad1s1
        # bsdlabel -e ad1s1
                a:      512M    *       4.2BSD 0 0 0
                b:      1024M   *       swap
                c:      *       *       unused		<--- don't change
                e:      2G      *       4.2BSD 0 0 0
                f:      2G      *       4.2BSD 0 0 0
                g:      10G     *       4.2BSD 0 0 0
                h:      *       *       4.2BSD 0 0 0
                ^KX (means: save & exit)
        # newfs /dev/ad1s1a
        # newfs -U /dev/ad1s1e
        # newfs -U /dev/ad1s1f
        # newfs -U /dev/ad1s1g
        # newfs -U /dev/ad1s1h

Stage 2: Go into SUM and prepare the source partitions
        # shutdown now
        # umount /home
        # umount /usr
        # umount /var
        # umount /tmp
        # mount -r /
        # fsck / /tmp /var /usr /home

Stage 3: Start dumping and restoring the partitions
        # mount /dev/ad1s1a /mnt
        # cd /mnt
        # dump -0 -f - /dev/ad0s1a | restore -r -f -
		At this point, /mnt will have the content of / and
		therefore the mountpoints for the other partitions,
		the former /tmp, /var, /usr and /home, will be
		available.
        # mount /dev/ad1s1e /mnt/tmp
        # cd /mnt/tmp
        # dump -0 -f - /dev/ad0s1e | restore -r -f -
        # mount /dev/ad1s1f /mnt/var
        # cd /mnt/var
        # dump -0 -f - /dev/ad0s1f | restore -r -f -
        # mount /dev/ad1s1g /mnt/usr
        # cd /mnt/usr
        # dump -0 -f - /dev/ad0s1g | restore -r -f -
        # mount /dev/ad1s1h /mnt/home
        # cd /mnt/home
        # dump -0 -f - /dev/ad0s1h | restore -r -f -

Stage 4: Umount disks and shut down the system
        # cd /
        # umount /mnt/home
        # umount /mnt/usr
        # umount /mnt/var
        # umount /mnt/tmp
        # umount /mnt
        # sync
        # shutdown -p now

Now you can take out the disk and use it in another computer.



-- 
Polytropon
Magdeburg, Germany
Happy FreeBSD user since 4.0
Andra moi ennepe, Mousa, ...