Copy-rootfs

This is a command to copy the current (running, live) root filesystem to another (attached) disk. Last tested with Debian 8.1 (Jessie) and all works fine.

• add the new disk (e.g. /dev/sdb) to the system
• set up a linux partition and make it active (enable boot flag)
• format the target filesystem to ext2
• mount the target filesystem to /mnt

• copy files across..

     (cd / ; tar -cf - . --one-file-system) | (cd /mnt ; tar xvfpB - )
     cp -r /dev/* /mnt/dev/

• find out new disk UUID (ls /dev/disk/by-uuid/....)

• update UUID's in fstab and grub.cfg

       sed -i 's/old-uuid/new-uuid/g' /mnt/etc/fstab
       sed -i 's/old-uuid/new-uuid/g' /mnt/boot/grub/grub.cfg

• install grub

      grub-install --root-directory=/mnt /dev/sdb

• shutdown system

• detach old disk

• move new disk to Primary Master (IDE)

• boot system with new disk

• reinstall grub one final time:

       update-grub
       grub-install /dev/sda

       -or-

       dpkg-reconfigure grub-pc

TROUBLESHOOTING

- at the blue grub menu, enter the edit mode (press 'e') and change the UUID=xxxx to /dev/sda1

- if you've forgotten to update the uuid, you can still boot the disk

grub rescue>
grub rescue> set prefix=(hd0,1)/boot/grub
grub rescue> insmod ext2
grub rescue> set root=(hd0,1)

(find out the kernel image name using ls, ls (hd0,1)/, ls (hd0,1)/boot)

grub rescue> linux /boot/vmlinuz-3.16.0-4-686-pae root=UUID=xxxxx ro recovery nomodeset
grub rescue> initrd /boot/initrd.img-3.16.0-4-686-pae
grub rescue> boot

(instead of the UUID you can also use 'root=/dev/sda1') (you can also remove 'ro recovery nomodeset')