On January 15, 2023 12:25:11 PM EST, H [off-list ref] wrote:

On 01/14/2023 10:12 PM, H wrote:

quoted

I need to transfer an existing CentOS 7 non-RAID setup using one

single SSD to a mdadm RAID1 using two much larger SSDs. All three disks
exist in the same computer at the same time. Both the existing SSD and
the new ones use LVM and LUKS and the objective is to preserve the OS,
all other installed software and data etc. Thus no new installation
should be needed.

quoted

Since all disks, partitions, LUKS etc have their unique UUIDs I have

not figured out how to do this and could use help and advice.

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In preparation for the above, I have:

- Used rsync with the flags -aAXHv to copy all files on the existing

SSD to an external harddisk for backup.

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- Partitioned the new SSDs as desired, including LVM and LUKS. My

configuration uses one RAID1 for /boot, another RAID1 partition for
/boot/efi, and a third one for the rest which also uses LVM and LUKS. I
actually used a DVD image of Centos 7 (minimal installation) to
accomplish this which also completed the minimal installation of the OS
on the new disks. It boots as expected and the RAID partitions seem to
work as expected.

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Since I want to actually move my existing installation from the

existing SSDs, I am not sure whether I should just use rsync to copy
everything from the old SSD to the new larger ones. However, I expect
that to also transfer all OS files using the old, now incorrect UUIDs,
to the new disks after which nothing will work, thus I have not yet
done that. I could erase the minimal installation of the OS on the new
disks before rsyncing but have not yet done so.

quoted

I fully expect to have to do some manual editing of files but am not

quite sure of all the files I would need to edit after such a copy. I
have some knowledge of linux but could use some help and advice. For
instance, I expect that /etc/fstab and /etc/crypttab would need to be
edited reflecting the UUIDs of the new disks, partitions and LUKS, but
which other files? Grub2 would also need to be edited I would think.

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The only good thing is that since both the old disk and the new disks

are in the same computer, no other hardware will change.

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Is there another, better (read: simpler) way of accomplishing this

transfer?

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Finally, since I do have a backup of the old SSD and there is nothing

of value on the new mdadm RAID1 disks, except the partition
information, I do have, if necessary, the luxury of multiple tries.
What I cannot do, however, is to make any modifications to the existing
old SSD since I cannot afford not being able to go back to the old SSD
if necessary.

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Thanks.

Upon further thinking, I am wondering if the process below would work?
As stated above, I have two working disk setups in the same computer
and depending on the order of disks in the BIOS I can boot any of the
two setups.

My existing setup uses one disk and no RAID (obviously), LUKS and LVM
for everything but /boot and /boot/efi, total of three partitions. The
OS is Centos 7 and I have made a complete backup to an external
harddisk using rsync ("BACKUP1").

The new one uses two disks, RAID1, LUKS and LVM for everything but
/boot and /boot/efi, total of four partitions (swap has its own
partition - not sure why I made it that way). A minimal installation of
Centos 7 was made to this setup and is working. In other words, UUIDs
of disks, partitions and LUKS are already configured and working.

So, I am now thinking the following might work:

- Make a rsync backup of the new disks to the external harddisk
("BACKUP2").

- Delete all files from the new disks except from /boot and /boot/efi.

- Copy all files from all partitions except /boot and /boot/efi from
BACKUP1 to the new disks. In other words, everything except /boot and
/boot/efi will now be overwritten.

- I would expect this system not to boot since both /etc/fstab and
/etc/crypttab on the new disks contain the UUIDs from the old system.

- Copy just /etc/fstab and /etc/crypttab from BACKUP2 to the new disks.
This should update the new disks with the previously created UUIDs from
when doing the minimal installation of CentOS 7.

What do you think?

I am happy to share that my plan as outlined below worked. I now have /boot, /boot/efi and / on separate RAID partitions with the latter managed by LVM and encrypted.  All data from the old disk is now on the new setup and everything seems to be working.

However, going back to the issue of /boot/efi possibly not being duplicated by CentOS, would not mdadm take care of that automatically? How can I check?