nix-files/doc/migrating-storage-device.md

migrating a host to a new drive

1. copy persistent data off of the host:

$ mkdir -p mnt old/persist
$ mount /dev/$old mnt
$ rsync -arv mnt/persist/ old/persist/

2. flash the new drive

$ nix-build -A hosts.moby.img
$ dd if=$(readlink ./result) of=/dev/$new bs=4M oflag=direct conv=sync status=progress

3.1. expand the partition

$ cfdisk /dev/$new
# scroll to the last partition
> Resize
  leave at default (max)
> Write
  type "yes"
> Quit

3.2. expand the filesystem

$ mkdir -p /mnt/$new
$ mount /dev/$new /mnt/$new
$ btrfs filesystem resize max /mnt/$new

4. copy data onto the new host

$ mkdir /mnt/$new
$ mount /dev/$new /mnt/$new
# if you want to use btrfs snapshots (e.g. snapper), then create the data directory as a subvolume:
$ btrfs subvolume create /mnt/$new/persist
# restore the data
$ rsync -arv old/persist/ /mnt/$new/persist/

5. ensure/fix ownership

$ chmod -R a+rX /mnt/$new/nix
# or, let the nix daemon do it:
$ nix copy --no-check-sigs --to /mnt/$new $(nix-build -A hosts.moby)

6. insert the disk into the system, and boot!