====== send / receive ======

grub-install --target=x86_64-efi --efi-directory=/target/@rootfs/boot/efi --boot-directory=/target/@rootfs/boot --bootloader-id=debian --recheck --no-floppy
update-grub 

mount --rbind /dev  /target/@rootfs/dev
mount --rbind /proc /target/@rootfs/proc
mount --rbind /sys  /target/@rootfs/sys
chroot /target/@rootfs /bin/bash --login

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=debian --recheck --no-floppy
Installing for x86_64-efi platform.
grub-install: error: cannot find a device for /boot/grub (is /dev mounted?).


===== migrate to new storage =====

Use Clonezilla live USB with latest 6.11 kernel.

There is a hole between Windows partitions and Windows recovery partitions:
<code>
parted /dev/nvme0n1
print free
Number  Start   End     Size    File system  Name                          Flags
        17.4kB  1049kB  1031kB  Free Space
 1      1049kB  106MB   105MB   fat32        EFI system partition          boot, esp, no_automount
 2      106MB   123MB   16.8MB               Microsoft reserved partition  msftres, no_automount
 3      123MB   60.3GB  60.2GB  ntfs         Basic data partition          msftdata
        60.3GB  511GB   451GB   Free Space
 4      511GB   512GB   944MB   ntfs         Basic data partition          hidden, diag, no_automount
        512GB   512GB   335kB   Free Space
</code>

So create 16GB swap at end and BTRFS for root part.

<code bash>
parted /dev/nvme0n1

mkpart swap sw 495G 511G
mkpart root btrfs 60.3GB  495GB
</code>

<code bash>
mkfs.btrfs /dev/nvme0n1p6
mkdir /target
mount /dev/nvme0n1p6 /target
</code>

<code bash>
sudo apt install netcat-openbsd pv zstd
</code>

==== rsync ====

Rsync send is not related to BTRFS, but here it can help if FS is ''ro'' state due to errors.

Recreate destination volumes

<code bash>
cd /target
btrfs sub create @rootfs
btrfs sub create @rootfs/home
btrfs sub create @rootfs/var
btrfs sub create @rootfs/var/log
btrfs sub create @rootfs/var/cache
btrfs sub create @rootfs/var/spool
btrfs sub create @rootfs/var/lib
btrfs sub create @rootfs/var/lib/docker
btrfs sub create @rootfs/var/snap
btrfs sub create @rootfs/opt
btrfs sub create @rootfs/usr
btrfs sub create @rootfs/usr/local

btrfs sub create @rootfs/home/user
btrfs sub create @rootfs/home/user/prj
btrfs sub create @rootfs/home/user/Documents
</code>

Rsync option explanation:
  * ''a'' --archive, -a archive mode is -rlptgoD (no -A,-X,-U,-N,-H)
    *        --recursive, -r          recurse into directories
    *        --links, -l
              When  symlinks are encountered, recreate the symlink on the des‐
              tination.
    *     --perms, -p              preserve permissions
    *        --times, -t              preserve modification times
    *        --group, -g              preserve group
    *        --owner, -o              preserve owner (super-user only)
    *        -D                       same as --devices --specials
      *        --devices                preserve device files (super-user only)
      *        --specials               preserve special files
  * ''v'' --verbose, -v increase verbosity
  * ''x'' --one-file-system, -x don't cross filesystem boundaries

  * ''H''       --hard-links, -H         preserve hard links
  * ''A''       --acls, -A               preserve ACLs (implies --perms)
  * ''X'' --xattrs, -X  preserve extended attributes
  * ''P'' -P                       same as --partial --progress
  * --numeric-ids            don't map uid/gid values by user/group name
  *       --whole-file, -W         copy files whole (w/o delta-xfer algorithm)

<file ini /etc/rsyncd.conf>
[rootfs]
        path = /target/@rootfs
</file>
rsync -v --daemon

on client, list rsync modules:

rsync 192.168.177.161::
rootfs         	


Now rsync but do not limit to one filesystem, to copy all subvolumes into its places (already created on dst):

<code bash>
rsync -avHAXPW --exclude=".snapshots" 192.168.177.161::rootfs /target/@rootfs
</code>

Try ssh to correct permission errors
<code bash>
rsync -avHAXPW --exclude=".snapshots" ssh://user@192.168.177.161/target/@rootfs/ /target/@rootfs
</code>

No need to add on not live FS:
<code>
--exclude='/dev' --exclude='/proc' --exclude='/sys'
</code>

Even if rsync daemon is started from root account (on src host) it cannot read some files according to normal permissions:
<code>
rsync: [sender] send_files failed to open "/var/spool/postfix/pid/unix.local" (in rootfs): Permission denied (13)
rsync: [sender] send_files failed to open "/var/spool/postfix/pid/unix.retry" (in rootfs): Permission denied (13)
rsync: [sender] send_files failed to open "/var/spool/postfix/pid/unix.smtp" (in rootfs): Permission denied (13)
</code>

workaround is to start rsync daemon on dst host with the same rsyncd.conf config and start rsync from src host:

<code bash>
rsync -avxHAXPW --exclude=".snapshots" /target/@rootfs 192.168.177.171::rootfs 
</code>


tar:
  * ''-c'' create
  * ''-p'', ''--preserve-permissions'', ''--same-permissions'' extract information about file permissions  (default  for  superuser)
  * ''-s'', '' --preserve-order'', ''--same-order'' Sort names to extract to match archive
  * ''-f'', ''--file=ARCHIVE'' Use  archive  file  or  device  ARCHIVE.   If this option is not given, tar will first examine the enviro
            
             
Sender:
<code bash>
#tar -czpsf - /target/@rootfs | pv -b | nc -l -p 44444
cd /target/@rootfs
tar --acls --xattrs -cpsf - . | zstd --fast -T0 | pv | nc -w 2 -N 192.168.177.171 44444
</code>

Receiver:
<code bash>
#nc 192.168.1.4 3333 | pv -b | tar --acls --xattrs -xzpsf -

cd /target/@rootfs
nc -vl 44444 | zstd -d | pv | tar -xpsf -

</code>

==== btrfs send ====

It can send only ''ro'' volumes. If FS is broken and forced ''ro'' you cannot set volumes to ''ro'' :)
Only possible to send  ''ro'' snapshots.

Sender:
<code bash>
btrfs property set -ts /target/@roots ro true
btrfs send /target/@rootfs | zstd --fast -T0 | pv | nc -w 2 -N 192.168.177.171 44444
</code>

Receiver:
<code bash>
nc -vl 44444 | zstd -d | pv | btrfs receive /target
</code>