Moving Ubuntu root to a new SSD which will become the boot device

Question

I have a Dell desktop which I bought used, at which time it was set up to dual boot Windows (on disk 0 - /dev/sda ) and Ubuntu (on disk 1 - /dev/sdb). I nuked the Windows installation and /dev/sda now contains data.

Fdisk shows:

Device         Start       End   Sectors   Size Type
/dev/sda1       2048   1023999   1021952   499M Windows recovery environment
/dev/sda2    1024000   1228799    204800   100M EFI System ( mounted at/boot/efi)
/dev/sda3    1228800   1261567     32768    16M Microsoft reserved
/dev/sda4    1261568 656621567 655360000 312.5G Microsoft basic data (really linux ext4 fs)
/dev/sda5  656621568 976773119 320151552 152.7G Linux filesystem (ext4)

I am purchasing an SSD which I want to use as the boot device (UEFI, not legacy) and which will contain the root partition. I want to clone the current root partition (/dev/sdb1) to the SSD rather than do a new install of Ubuntu, so I can preserve all customizations and configuration.

I assume the steps, in order, are

1. Format SSD, create empty GPT partition table (maybe it will have one ???)
2. Create required partitions on SSD - EFI (fat32), root (ext4)
3. Populate EFI (grub-install ?)
4. Copy root from /dev/sdb to SSD

I'm not at all sure how to proceed - should I do all this from a liveUSB of my current Ubuntu (22.04) ? Once I've copied the existing root partition to the SSD I assume I'll need to tweak /etc/fstab ? Are there any other gotchas ?

I'd appreciate a sanity check and feedback.

TIA.

Answer 1

You have some of your steps out of order and there are a few pieces missing here, but the general idea you have is good.

Firstly, yes, you will want to use a live USB to do the cloning. You should have every file on your root partition "at rest" (i.e., no program actively using it) while cloning things.

Next, you are right about first making an EFI partition and then a root partition. However, this will give you two EFI partitions, one on your old disk and one on the new one, which could cause confusion. We can deal with that part at the end.

The next step is not the grub-install step. Rather, this is when you want to do the cloning. From a live USB, you'll want to do something like this:

cd /mnt
mkdir source
mkdir dest
sudo mount /dev/sdXY ./source    # this isn't guaranteed to be sdb1 anymore, so check it with lsblk first!
sudo mount /dev/sdAB ./dest
sudo cp -a ./source/. ./dest/.   # the slashes and periods are important here

That last command will take a while to run, depending on how much it has to copy. This will copy over all of the files on your root partition to the new partition, preserving as much info as possible, including file permissions. (Do NOT use cp -r here, it will mangle file permissions and you'll almost certainly get a broken clone. cp -a is the way.)

Once that finishes, your clone is done, but you're not quite out of the woods yet. You still have to install the bootloader, but also, you will have to tweak /etc/fstab. This is the file that tells Linux what to mount and where to mount it during bootup. Usually /etc/fstab identifies your root partition via UUID, and your partition's UUID will be different than it used to be.

To figure out your partition's UUID, use lsblk -f. This will display a bunch of partition info, including the UUIDs. Find the UUID of your destination drive, and copy it into a text file.

Next, run "sudo nano /mnt/dest/etc/fstab", and find the line that mounts your root partition (it will have a single / as the mountpoint). Replace the UUID in this line with the UUID of the new partition that you found earlier. Then press Ctrl+S to save, and Ctrl+X to exit.

Now we can install the bootloader. Mount the new EFI partition using sudo mount /dev/sdAC /mnt/dest/boot/efi (replacing AC as appropriate). Then you should be able to install the bootloader with a command like this:

sudo grub-install --target x86_64-efi --efi-directory /mnt/dest/boot/efi --boot-directory /mnt/dest/boot

And lastly, generate the GRUB configuration:

sudo grub-mkconfig -o /mnt/dest/boot/grub/grub.cfg

With that complete, shut down the computer, disconnect the old drive to keep the old EFI partition from causing confusion, and then try and boot into the cloned installation. If you can boot successfully, you hopefully should be good to go!