New post on copying the drive on a running machine.

content/onlide-disk-copy.rst

+
+Copy a drive on a running machine
+#################################
+:date: 2024-06-08
+:summary: Copying to a new drive while the machine is running
+
+I was close to running out of disk space the homelab machine I use for running
+services with personal data that I run in my home (I feel more comfortable
+having physical control). I was too lazy to connect the machine to a monitor
+and keyboard and rebooting from a thumbdrive so I tried to copy the old drive
+to a new drive while the machine was running. Here's what I did:
+
+#. Stop running processes that have open files. For me it was stopping Docker
+   containers, some services (I have most services running in containers so I
+   have few services).
+
+   .. code:: shell
+
+        docker container ls | awk 'NR>1 {print $1}' | xargs docker stop
+        sudo systemctl stop fwupd.service systemd-timesyncd.service docker.service docker.socket containerd.service cron.service systemd-journald.service systemd-journald.socket systemd-journald-dev-log.socket
+
+
+#. :code:`cd` to a directory on a different drive to avoid keeping the path
+   open :code:`cd /tmp`. Remount all partitions as read-only: :code:`sudo mount
+   --all -o remount,ro -t vfat,btrfs,ext4`. This may fail and you will see an
+   error with a path that couldn't be remounted due to open files. Run
+   :code:`lsof /path/that/has/open/files`, find the processes that still have
+   open files and either stop that service or kill the process (stopping the
+   service is better as it won't get restarted). Repeat until the partitions
+   are mounted read-only. Verify with the :code:`mount` command. Run
+   :code:`sudo sync` and now you should be able to copy the drive as there
+   won't writes to it while copying and the copy will be consistent.
+
+#. Start a session on the host using :code:`tmux` and copy
+   :code:`dd if=/dev/sda of=/dev/nvme0n1`. Now we wait.
+
+#. Once the copy is complete, run :code:`sudo sync` again and :code:`echo 1 |
+   sudo tee /sys/block/nvme0n1/device/rescan`. Now we need to resize the data
+   partition, `sudo parted /dev/nvme0n1 --script resizepart 3 100%` (in my case
+   the data partition was the 3rd partition after the EFI and root partitions).
+   Open the encrypted partition :code:`sudo cryptsetup open /dev/nvme0n1p3
+   _dev_nvme0n1p2` and resize the encrypted partition :code:`sudo cryptsetup
+   resize _dev_nvme0n1p3`. Last resize is the filesystem in the encrypted
+   partition, we mount it :code:`sudo mount /dev/mapper/_dev_nvme0n1p3 /mnt`
+   and resize it :code:`sudo btrfs filesystem resize max /mnt`. Umount the data
+   partition :code:`sudo umount /mnt`.
+
+#. Let's reinstall the boot loader.
+
+   .. code:: shell
+
+        sudo mount /dev/nvme0n1p2 /mnt
+        sudo mount /dev/nvme0n1p1 /mnt/boot/efi
+        for dir in dev proc sys; do sudo mount --bind "/${dir}" "/mnt/${dir}"; done
+        sudo chroot /mnt
+        grub-install /dev/nvme0n1
+        exit
+        for dir in dev proc sys; do sudo umount "/mnt/${dir}"; done
+        umount /mnt/boot/efi
+        umount /mnt
+
+#. Because we copied the existing partitions, their UUIDs will remain the same
+   so there's no need to update mounts. Stop the machine, remove the old drive
+   and boot. With a little luck the UEFI BIOS will not need configuration to
+   use the new drive and the machine will boot happily.