How to Migrate the Root Filesystem to a New Disk
This document (7018639) is provided subject to the disclaimer at the end of this document.
2. Copy data at the block(a) or filesystem(b) level depending on preference from the old disk to the new disk.
NOTE: If the dd command is not being used to copy data from an entire disk to an entire disk the partition(s) will need to be created prior to this step on the new disk so that the data can copied from partition to partition.
a. Here is a dd command for copying at the block level (the disks do not need to be mounted):
# dd if=/dev/<old root disk> of=/dev/<new root disk> bs=64k conv=noerror,sync
The dd command is not verbose and depending on the size of the disk could take some time to complete. While it is running the command will look like it is just hanging. If needed, to verify it is still running, use the ps command on another terminal window to find the dd command's process ID and use strace to follow that PID and make sure there is activity.
# ps aux | grep dd
# strace -p<process id>
After confirming activity, hit CTRL + c to end the strace command. Once the dd command is complete the terminal prompt will return allowing for new commands to be run.
b. Alternatively to dd, mount the disks and then use an rsync command for copying at the filesystem level:
# mount /dev/<old root disk> /mnt
# mkdir /mnt2
(If the new disk's root partition doesn't have a filesystem yet, create it now.)
# mount /dev/<new root disk> /mnt2
# rsync -zahP /mnt/ /mnt2/
This command is much more verbose than dd and there shouldn't be any issues telling that it is working. This does generally take longer than the dd command.
3. Setting up the partition boot label with either fdisk(a) or parted(b)
NOTE: This step can be skipped if the boot partition is separate from the root partition and has not changed. Also, if dd was used on an entire disk to an entire disk in section "a" of step 2 you can still skip this step since the partition table will have been copied to the new disk (If the partitions are not showing as available yet on the new disk run "partprobe" or enter fdisk and save no changes. ). This exception does not include using dd on only a partition.
a. Using fdisk to label the new root partition (which contains boot) as bootable.
# fdisk /dev/<new root disk>
From the fdisk shell type 'p' to list and verify the root partition is there.
Command (m for help): p
If the "Boot" column of the root partition does not have an "*" symbol then it needs to be activated. Type 'a' to toggle the bootable partition flag:
After that use the 'p' command to verify the bootable flag is now enabled. Finally, save changes:
b. Alternatively to fdisk, use parted to label the new root partition (which contains boot) as bootable.
# parted /dev/sda
From the parted shell type "print" to list and verify the root partition is there.
After that use the "print" command again to verify the flag is now listed for the root partition. then exit parted to save the changes:
NOTE: Steps 4 through 6 will need to be done in a chroot environment on the new root disk. TID7018126 covers how to chroot in rescue mode: https://www.suse.com/support/kb/doc?id=7018126
a. Updating Legacy GRUB on SLE11
# vim /boot/grub/menu.lst
There are two changes that may need to occur in the menu.lst file.
Since the sd[a-z] device names are not persistent it's recommended to find the equivalent /dev/disk/by-id/ or /dev/disk/by-path/ disk name and to use that instead. Also, the device name might be different in chroot than it was before chroot. Run this command to verify the disk name in chroot:
2. in the line starting with the word "kernel" (generally just below the root line we just went over) there should be a root=/dev/<old root disk> parameter. That will need to be updated to match the path and device name of the new root partition. root=/dev/disk/by-id/<new root partition> Also, if the swap partition was changed to the new disk you'll need to reflect that with the resume= parameter.
( you may get a warning message about the boot loader. This can be ignored.)
Go to the "Boot Loader Installation" tab with ALT + a. Verify it is set to boot from the correct partition. For example, if the content of /boot is in the root partition then make sure it is set to boot from the root partition. Lastly hit ALT + o so that it will save the configuration. While the YaST2 module is existing it should also install the boot loader.
The parameter to update is the GRUB_CMDLINE_LINUX_DEFAULT. If there is a "root=/dev/<old root disk>" parameter update it so that it is "root=/dev/<new root disk>". If there is no root= parameter in there add it. Each parameter is space separated so make sure there is a space separating it from the other parameters. Also, if the swap partition was changed to the new disk you'll need to reflect that with the resume= parameter.
Since the sd[a-z] device names are not persistent it's recommended to find the equivalent /dev/disk/by-id/ or /dev/disk/by-path/ disk name and to use that instead. Also, the device name might be different in chroot than it was before chroot. Run this command to verify the disk name in chroot before comparing with by-id or by-path:
After saving changes to that file run this command to save them to the GRUB2 configuration:
After that run this command on the disk with the root partition. For example, if the root partition is sda2 run this command on sda:
# grub2-install /dev/<disk of root partition>
5. Correct the fstab file to match new partition name(s)
# vim /etc/fstab
Correct the root (/) partition mount row in the file so that it points to the new disk/partition name. If any other partitions were changed they will need to be updated as well. For example, changed from:
The 3rd through 6th column may vary from the example. The important aspect is to change the row that is root (/) on the second column and adjust in particular the first column to reflect the new root disk/partition. Save and exit after making needed changes.
6. Lastly, run the following command to rebuild the ramdisk to match updated information:
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- Document ID:7018639
- Creation Date: 17-Feb-2017
- Modified Date:03-Mar-2020
- SUSE Linux Enterprise Desktop
- SUSE Linux Enterprise Server
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