Cloning a Linux server - general method

Jephe Wu http://linuxtechres.blogspot.com

Last time, we talked about using dd to do Linux server cloning for the same kind of hardwares - Cloning a Linux server - scenery 1. This time, we will introduce another general method for doing Linux server cloning.

I assume the source is using the normal partition which means it's not using software raid, LVM etc. For cloning Linux server with LVM partition, please check my another article at http://linuxtechres.blogspot.com/2007/08/clone-linux-server-with-lvm2-partition.html . My test environment is as follows:

the source:
a. HP DL380 (Intel Xeon CPU)
b. Redhat Enterprise Linux 4

the destination:
a. HP DL385G2 AMD64

The following are the cloning steps:

1. boot up the destination server from RIP(Recovery Is Possible) CD
You can choose the second options in GRUB bootup menu to load everything into memory and skip keyboard map option, then you can eject CD out before doing the following if you'd like to.

2. configure the IP address for the destination server( we use 192.168.0.101 here)
ifconfig eth0 192.168.0.101 up

2. copy over the 3 files from the source(assuming server name is linuxtechres, the IP is 192.168.0.100)
scp 192.168.0.100:/etc/passwd /etc/
scp 192.168.0.100:/etc/shadow /etc/
scp 192.168.0.100:/etc/group /etc/

3. clone the partition table over using sfdisk
Assuming /dev/cciss/c0d0p1 is / partition, /dev/cciss/c0d0p2 is the /boot partition.

ssh 192.168.0.100 'sfdisk -d /dev/cciss/c0d0' | sfdisk /dev/cciss/c0d0
mkfs -t ext3 /dev/cciss/c0d0p1
e2label /dev/cciss/c0d0p1 /
mkfs -t ext3 /dev/cciss/c0d0p2
e2label /dev/cciss/c0d0p2 /boot
Note: check your source server /etc/fstab so that you know why we use e2label to label the partition / and /boot. That's the default label name by Redhat Enterprise Linux for / and /boot partitions.
cd /mnt
mount /dev/cciss/c0d0p1 hd
cd hd
mkdir boot proc sys mnt ...
mount /dev/cciss/c0d0p2 boot
note: if you have some more partitions like /usr and /home etc, make sure you make file system for all partitions and give the correct label as what the source has, similar as the above steps.

4. clone everything over now
cd /mnt/hd
ssh 192.168.0.100 'cd /; tar --exclude ./proc --exclude ./sys --exclude ./mnt -cpf - .' | tar xvpf -
note: you might want to exclude some data folder or partitions also so that you can finish the cloning process earlier, after that, you can copy the data folder/partition separately. see the step 8
cd etc
rm -f blkid.tab mtab (because they will be generated by OS each time it boots up)
vi sysconfig/network-scripts/ifcfg-eth* ( to comment out hardware address lines and change ip address line to the destination IP)

5. install GRUB (if both the source and the destination are x86 32bit)
cd /mnt/hd
chroot .; grub_install hd0
In my case, I skiped this step and use step 7 to install GRUB since the destination is AMD64 CPU

6. umount those partition that you mounted before
exit (exit from chroot environment)
cd /mnt/hd
umount boot mnt
cd /mnt
umount hd
sync;sync;sync
reboot

7. install GRUB on AMD64 servers
If you are cloning from x86_32 server to x86_64 server like AMD64, you have to
boot from the first x86_64 RedHat Enterprise Linux 4 CD to install GRUB
chroot /mnt/sysimage;grub_install hd0

8. rsync over the data partitions
after the OS boots up, you can use rsync to copy the data folder or partition over.
rsync -e ssh -P -avz source_ip_addr:/data/ /data/

That's it. Now you can bring up one more server which is exactly the same as the source.


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