Migrating and re-building Linux systems (P2V) with cpio

this is obsolete doc -- see http://doc.nethence.com/ instead

On the source server

On the source server, check out the mount points and finely select only the needed folders from the root directory,

mount

df -h

cd /

ls -1

Proceed with the system live backup,

srvname=DEFINE_SERVER_NAME

unalias ls

folders=`ls -1 | egrep -v '^mnt_srvinstall|^net|^proc|^sys'`

time find $folders -depth | grep -v lost+found | cpio -o > /mnt_srvinstall/$srvname.rootdir.cpio

unset folders

Write down the number of blocks that have been copied.

On the destination server

Create the virtual machine with same hardware attributes, but disable the network at power on. Start the emtpy VM, load the SystemRescueCD image and enable networking for this run.

Once SystemRescueCD has started on the destination server, eventually access it remotely,

net-setup

ifconfig

passwd root

You can now connect remotely as root.

Then look for available disks,

fdisk -l

Create partitions on the system disk (at least / and a swap partition and eventually a first one for /boot),

cfdisk /dev/sda

Create /dev/sda1 for /

Create /dev/sda2 for swap

Make /dev/sda2 type swap

Make /dev/sda1 bootable

Format the partitions and swap,

mke2fs -I 128 /dev/sda1

mkfs.ext3 /dev/sda2

mkswap /dev/sda3

Note. not using ext4 because of an error when initramfs is trying to load ext, see troubleshooting.

Note. using inode size 128 otherwise we get a error at grub-install, see troubleshooting.

Mount the filesystems,

mount /dev/sda2 /mnt/

mkdir -p /mnt/boot/

mount /dev/sda1 /mnt/boot/

Restore the archive on the new server,

srvname=DEFINE_SERVER_NAME

mkdir -p /mnt_srvinstall/

mount -t nfs4 srvinstall:/var/ftp /mnt_srvinstall/

cd /mnt/

time cpio -id < /mnt_srvinstall/$srvname.rootdir.cpio

Check that the number of blocks corresponds.

Create the folders that have been excluded,

mkdir -p net/ proc/ sys/

Check the time on the lost+found folder -- it should be the new one the local file system and not the one from the cpio archive (this has been taken care of at archive's creation stage anyway),

find . -type d | grep lost+found

ls -ld ./lost+found

Enter the freaking chroot,

mount -o bind /proc /mnt/proc

mount -o bind /dev /mnt/dev

chroot /mnt/ /bin/bash

Reinstall GRUB (fstab and initrd can be fixed afterwards),

grub-install /dev/sda

Edit the fstab,

cd /etc/

cp fstab fstab.beforep2v

vi fstab

proc /proc proc defaults 0 0

/dev/sda1 /boot ext2 defaults 1 2

/dev/sda2 / ext3 defaults 1 1

/dev/sda3 none swap sw 0 0

/dev/cdrom /media/cdrom0 udf,iso9660 user,noauto 0 0

#srvinstall:/var/ftp /mnt_srvinstall nfs4 defaults 0 0

note. also the cdrom device has been tuned.

get rid of the old mtab TODO CHECK CREATED,

mv mtab mtab.beforep2v

Rebuild the initramfs,

mkdir -p ~/.trash/

ls -l /boot/vmlinuz*

mv -f /boot/initrd* ~/.trash/

update-initramfs -c -k 2.6.26-2-686

Note. no need to re-update grub after that.

Fix the (old) GRUB configuration,

cd /boot/grub/

cp menu.lst menu.lst.beforep2v

vi menu.lst

Remove the old kernels from the list

Fix the kernel and initrd path (remove /boot)

Fix the rootdir path (switch to /dev/sda2)

for example as a result,

title Debian GNU/Linux, kernel 2.6.26-2-686

root (hd0,0)

kernel /vmlinuz-2.6.26-2-686 root=/dev/sda2 ro

initrd /initrd.img-2.6.26-2-686

title Debian GNU/Linux, kernel 2.6.26-2-686 (recovery mode)

root (hd0,0)

kernel /vmlinuz-2.6.26-2-686 root=/dev/sda2 ro single

initrd /initrd.img-2.6.26-2-686

Ready to reboot, but make sure you disable network first,

umount /mnt_srvinstall/

DISABLE NETWORK UNLESS THE SOURCE SERVER IS OFFLINE ALREADY

sync

shutdown -r now

Troubleshooting

An alternate way to re-install grub on the device,

grub

root (hd0,0)

setup (hd0)

If you need to re-install the grub package itself,

#apt-get install --reinstall grub

If you get this error message at grub-install stage,

The file /boot/grub/stage1 not read correctly.

==> use inode size 128 on the boot partition.

Refs.

http://kb.kristianreese.com/index.php?View=entry&EntryID=113

https://wiki.archlinux.org/index.php/Talk:GRUB_Legacy

At startup even before grub loads the system, if you get this error,

Error 15: File not found

==> fix menu.lst or the menu at boot time to get rid of /boot

At startup at initramfs stage, if you get this error,

mount: mountint /dev/ on /root/dev failed: No such file or directory

==> make sure the root= argument points to the right partition in menu.lst or the grub menu

At startup at initramfs stage, if you get this error,

ext3-fs couldn't mount because of unsupported optional features (240)

==> As a workaround I used ext3 for the root device instead of ext4. I tried to add rootfstype=ext4 to the boot options but that did not work.

Ref. https://forums.gentoo.org/viewtopic-p-7259024.html