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install: more comprehensive subdivision of btrfs subvols (MR 2233)

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Why
Btrfs has some goodness (snapshots, switching between different rw snapshot)
which plays particularly well with certain "subvolume layouts".

What
This MR seeks to implement such a layout, namely a flat btrfs layout,
where the top level subvolume (i.e. the btrfs filesystem/partition itself)
remains unmounted in all situations,
except when making changes to direct child subvolumes of the filesystem.

- rename all subvols to follow the common @* btrfs subvol naming scheme.
- add subvol @root, because roots home directory shouldn't be rolled back.
- make subvol @var not Copy-on-Write (nodatacow) to avoid write
- multiplication on logs, VMs, databases, containers and flatpaks.
- add subvol @snapshots because that lets us change the root subvol to a
read-write snapshot of @ without affecting snapshots.
- add subvol @srv because it contains data for Web and FTP servers,
which shouldn't roll back together with root subvol.
- add subvol @tmp because we don't want to snapshot temporary files.
This subvol remains unmounted on the device,
unless conditions as laid out in pmaports!4737 are met.
- add check and error for btrfs when using rsync installation.
This commit is contained in:
Jacob Ludvigsen 2024-01-18 13:14:17 +01:00 • committed by Oliver Smith
parent e139a34472
commit 2bd1eb26d8
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GPG key ID: 5AE7F5513E0885CB
3 changed files with 79 additions and 12 deletions
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15
pmb/install/_install.py
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@ -153,10 +153,8 @@ def create_home_from_skel(args):
Create /home/{user} from /etc/skel
"""
rootfs = args.work + "/chroot_native/mnt/install"
if args.filesystem == "btrfs":
pmb.helpers.run.root(args,
["btrfs", "subvol", "create", rootfs + "/home"])
else:
# In btrfs, home subvol & home dir is created in format.py
if args.filesystem != "btrfs":
pmb.helpers.run.root(args, ["mkdir", rootfs + "/home"])
homedir = rootfs + "/home/" + args.user
if os.path.exists(f"{rootfs}/etc/skel"):
@ -779,9 +777,12 @@ def create_fstab(args, layout, suffix):
# btrfs gets separate subvolumes for root, var and home
fstab = f"""
# <file system> <mount point> <type> <options> <dump> <pass>
{root_mount_point} / {root_filesystem} subvol=root,compress=zstd:2,ssd 0 0
{root_mount_point} /home {root_filesystem} subvol=home,compress=zstd:2,ssd 0 0
{root_mount_point} /var {root_filesystem} subvol=var,compress=zstd:2,ssd 0 0
{root_mount_point} / btrfs subvol=@,compress=zstd:2,ssd 0 0
{root_mount_point} /home btrfs subvol=@home,compress=zstd:2,ssd 0 0
{root_mount_point} /root btrfs subvol=@root,compress=zstd:2,ssd 0 0
{root_mount_point} /srv btrfs subvol=@srv,compress=zstd:2,ssd 0 0
{root_mount_point} /var btrfs subvol=@var,ssd 0 0
{root_mount_point} /.snapshots btrfs subvol=@snapshots,compress=zstd:2,ssd 0 0
{boot_mount_point} /boot {boot_filesystem} defaults 0 0
""".lstrip()