Cloning or duplicating a running system using dump/restore

[FBSD]

Cloning or duplicating a running system
using dump/restore.

Assumptions:

The dump command will be issued from a host running in multiple-user-mode.
The host is a default configuration. IE: / as “a” partition, /var as “d” partition, /tmp as “e” partition
and /usr as “f” partition. We will dump from the hard drive where the running system is installed
to a second hard drive cabled to the motherboard or an external USB cabled hard drive or a
USB memory stick of sufficient size. Whatever the target media is, all the data currently on it will
be destroyed by this procedure. Even the MBR (Master Boot Record) will be recreated.
For this example /dev/ad0 is the hard drive where the live system is running.
The target is an USB flash stick /dev/da0.

The following is the sequence of commands used

Collect live file system sizes and save

 
df -h > liveFSsizes
cat liveFSsizes

Collect live file system sizes and save
Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a    496M    169M    287M    37%    /
devfs          1.0K    1.0K      0B   100%    /dev
/dev/ad0s1d    1.5G     26M    1.4G     2%    /var
/dev/ad0s1e    496M     10K    456M     0%    /tmp
/dev/ad0s1f     15G    410M     13G     3%    /usr

Collect live Slice Partition sizes and save
Bsdlabel lists the live Slice Partition sizes to a file
This file will be used later to allocate the slice partitions to the target

 
bsdlabel ad0s1 > liveSPsizes
cat liveSPsizes

Collect live Slice Partition sizes and save
# /dev/ad0s1:
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a:  1048576        0    4.2BSD        0     0     0
  b:  2291584  1048576      swap
  c: 39862305        0    unused        0     0         
  d:  3241984  3340160    4.2BSD        0     0     0
  e:  1048576  6582144    4.2BSD        0     0     0
  f: 32231585  7630720    4.2BSD        0     0     0

If you want to increase or decrease the partition allocation space sizes edit
the liveSPsizes.usb file. I have edited this changing partition sizes so it will fit on
a 2GB USB stick. You can see from the df –h output that the default sizes
sysinstall calculates leaves a lot of free space in the partitions.

# /dev/da0s1: 2GB USB flash drive stick
8 partitions:
#        size   offset    fstype   [fsize bsize bps/cpg]
  a:     300M        *    4.2BSD        0     0     0   # ad0s1a /
  b:     200M        *      swap                        # ad0s1b swap
  c:        *        *    unused        0     0         # whole thing
  d:      50M        *    4.2BSD        0     0     0   # ad0s1d /var
  e:     100M        *    4.2BSD        0     0     0   # ad0s1e /tmp
  f:        *        *    4.2BSD        0     0     0   # ad0s1f /usr

Zero out the target MBR destroying all the data on the target

dd if=/dev/zero of=/dev/da0 count=2

fdisk the target with a new MBR.

fdisk -BI /dev/da0

The –B means Reinitialize the boot code contained is sector 0 of the disk
Default from /boot/mbr
The ‘I’ means initialize sector 0 slice table for one slice covering the entire disk.
You will get 2 messages.
Fdisk: invalid fdisk partition table found
Fdisk: Class not found
Disregard these messages, they are the result of zeroing out the old MBR.

Label the target:

bsdlabel -B -w da0s1

The –B means bootstrap code will be read from the file /boot/boot and written to the disk
The –w means write a standard label

Allocate the partitions
Restore the partition sizes as defined in the file liveSPsizes

bsdlabel -R -w da0s1 liveSPsizes

Format all the new empty file system on the target.

 
newfs –U /dev/da0s1a # / 
newfs -U /dev/da0s1d # /var
newfs -U /dev/da0s1e # /tmp
newfs -U /dev/da0s1f # /usr

Mount target file system ‘a’ / and clone

 
mount /dev/da0s1a /mnt
cd /mnt
dump -0Lauf - /dev/ad1s1a | restore -rf -

Flags, -0 means do full dump,
-L means take snapshot because source is live file system,
-a means enforce writing until a end-of media is reached
-u means update the /etc/dumpdates file with the results
-f - means standard output is where the dumped data is to be written.
You can thing of 'standard output' as a un-named virtual file or buffer.
If there was no pipe | to the restore program the dumped data
would roll across the terminal screen.

The restore program, on the other side of the | pipe, usually reads 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 is currently positioned. In the example the current working directory is /mnt where the target file system. ‘a’ is mounted The –r flag means rebuild the file system. The restored file system will be of the same size as the one dumped including its free space it you did not change the content of the (liveSPsizes) file. In reality what we have with the above dump command is as dump writes a block of data to standard output its immediately handed to restores standard input and written to the target. The above snippet of code would have to be duplicated for each file system you wanted to dump.

The following (fbsd2clone) script employs the sample code snippet detailed above.

#!/bin/sh
# This script will use dump/restore to clone your running
# system to another motherboard cabled hard drive or
# USB cabled hard drive or USB flash stick.
# This is run as root. 
#
# Change these device unit pre-fixs in the code below as needed
#     ad0 is the live file system
#     da0 is the target
 
 
echo "Collect live file system sizes and save"
df -h  > liveFSsizes
cat liveFSsizes
 
echo "  "
echo "  "
echo "Collect live Slice Partition sizes and save"
bsdlabel ad0s1 > liveSPsizes
cat liveSPsizes
echo "  "
echo "  "
cat liveSPsizes.usb
 
# At this point you can edit the liveSPsizes files and 
# increase or decrease the file system partition sizes
# man bsdlabel for details
 
echo "  "
echo "  "
echo "Prepare the target"
dd if=/dev/zero of=/dev/da0 count=4
fdisk -BI /dev/da0
bsdlabel -B -w da0s1
bsdlabel -R da0s1 liveSPsizes.usb
newfs -U /dev/da0s1a
newfs -U /dev/da0s1d 
newfs -U /dev/da0s1e 
newfs -U /dev/da0s1f 
 
echo "  "
echo "  "
echo "Mount target file system 'a' / and clone"
mount /dev/da0s1a /mnt
cd /mnt
dump -0Lauf - /dev/ad0s1a  | restore -rf -
 
echo "  "
echo "  "
echo "Mount target file system 'd' /var and clone"
mount /dev/da0s1d /mnt/var
cd /mnt/var  
dump -0Lauf - /dev/ad0s1d  | restore -rf -
 
echo "  "
echo "  "
echo "Mount target file system 'e' /tmp and clone"
mount /dev/da0s1e /mnt/tmp
cd /mnt/tmp
dump -0Lauf - /dev/ad0s1e  | restore -rf -
 
echo "  "
echo "  "
echo "Mount target file system 'f'/usr  and clone"
mount /dev/da0s1f /mnt/usr
cd /mnt/usr
dump -0Lauf - /dev/ad0s1f  | restore -rf -
 
echo "  "
echo "  "
echo "Clean up"
sync
cd /root
umount /mnt/usr
umount /mnt/tmp
umount /mnt/var
umount /mnt
 
echo " Script completed"