Copying a FreeBSD install to a smaller disk
jerrymc at msu.edu
Fri Sep 12 16:12:21 UTC 2008
On Thu, Sep 11, 2008 at 05:19:55PM -0700, Chris Weiss wrote:
> How would I go about copying an existing FreeBSD installation to a smaller disk?
> I've got a 3rd FreeBSD install I can boot from and store temporary
> files on, all the disks are in the same hardware, so there's no
> reconfiguration other than the boot device name and interface (IE
> -SATA ad4 will become IDE ad0). The disk is partitioned using the
> "default" sysinstall values and the contents of the larger disk will
> fit on the smaller disk, although I need to increase the size of the /
> and /var slices on the target to hold everything (/usr is fairly
> empty, so it'll easily fit on the smaller disk).
> For now, we'll say ad0 = new smaller disk, ad4 = boot BSD disk, and
> ad6 = the BSD install I want to clone.
> The path I've been going down is to manually partition and slice ad0
> create ad4/mnt/source and ad4/mnt/target and mount /var, /tmp, etc
> from ad0 and ad6 and manually copy the files. But I'm stuck on how to
> handle /, since it'll have dev and proc and such.
> Any thoughts on how to do this, or on a completely different approach?
> I'm not aware of any 3rd party tools that'll deal with shrinking
> FreeBSD partitions.
> Thanks in advance for any help you folks can give!
Seems like you are generally on the right track, though some of your
mounting seems backwards to me.
First, as you have indicated, manually slice, partition and newfs
the new disk (ad0) to match what you want to have on it. If you
are making an identical, just smaller, disk to ad4, then do a df
and see what slices and partitions are being used on ad4. Probably
it is one slice, divided into several partitions.
While you are at it, look at each of the filesystem sizes and make
sure you will have room on the new, smaller disk. You want at least
the current used size + 10%. Really you want more to actually
Presuming you want a single bootable slice (ad0s1) which is then
divided in to partitions for:
fdisk -BI ad0
Creates a single bootable slice with default MBR (good enough).
bsdlabel -w -B da0s1
Writes an initial label and boot block on the slice
bsdlabel -e da0s1
Puts you in edit (vi by default) with the current condition of
the partition label showing. If it is new, it will only show
a 'c' partition covering the whole available size of the slice.
Edit this page by duplicating that 'c' line for each real partition
you want to have and changing fstype from 'unused' to '4.2BSD' on
the a, d, e, f, g partitions and 'swap' on the b partition.
In the end you will have something that looks about like:
# size offset fstype [fsize bsize bps/cpg]
a: 524288 0 4.2BSD 2048 16384 32776
b: 2572288 * swap
c: 78316875 0 unused 0 0 # "raw" part, don't edit
d: 1048576 * 4.2BSD 2048 16384 8
e: 4194304 * 4.2BSD 2048 16384 28552
f: 6291456 * 4.2BSD 2048 16384 28552
g: * * 4.2BSD 2048 16384 28552
You need only specify the sizes. You can put '*' for the offset
and the bsdlabel utility figures it out correctly.
Also, you can put '*' for both size and offset on the last
partition and it will use all the remaining available space.
Don't do anything with the actual 'c' partition.
Remember that sizes here are in 512 Byte blocks/sectors.
The sizes I have here are for a disk I happen to have handy at
the moment to look at.
a: 256 MB Mount as; /
b: 1,256 MB swap
d: 512 MB " " /tmp
e: 2,048 MB " " /usr
f: 3,072 MB " " /var
g: 31,096 MB " " /home
Then do a regular newfs on each real file system a, d, e, f, g
etc for e, f, g
Once you have the new disk created, I would do the rest all in
single user mode.
Boot to single useri, then
mount -u /
Create temporary mount points for the new filesystems (ignore /tmp
unless you actually have something there to maintain - unlikely)
Use dump/restore to copy the file systems
dump -0af - / | restore -rf -
dump -0af - /usr | restore -rf -
dump -0af - /var | restore -rf -
dump -0af - /home | restore -rf -
These can take a while, especially the /home dump/restore if
it is large.
Once you are finished with this you need to fix up
the /etc/fstab file on /newroot.
After this, when you reboot, as long as ad0 is in front of ad4 in
the BIOS boot sequence, the system will attempt to boot from ad0.
Since there are more than one bootable disks now on the machine,
it should give you a menu of bootable slices from which you can select.
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