Workaround to convert simple tar backup to borg backup, without leading path, using ratarmount (should works with archivemount too) and mergerfs

borg_chroot.sh

mkdir -p /chroot_tmp/{logs,mnt,archive_mnt,bins_mnt/dev,bins_mnt/lib,bins_mnt/lib64,bins_mnt/tmp/repo}

cd /chroot_tmp

wget https://github.com/borgbackup/borg/releases/download/1.1.10/borg-linux64 -O /bins_mnt/tmp/borg
chmod +x /chroot_tmp/bins_mnt/tmp/borg
wget https://www.busybox.net/downloads/binaries/1.31.0-defconfig-multiarch-musl/busybox-x86_64 -O /bins_mnt/tmp/busybox
chmod +x /chroot_tmp/bins_mnt/tmp/busybox
wget https://github.com/mxmlnkn/ratarmount/raw/master/ratarmount.py -O ratarmount.py
wget https://github.com/fusepy/fusepy/raw/master/fuse.py -o fuse.py

bins_mnt/tmp/borg init --verbose --progress --encryption=repokey-blake2 /chroot_tmp/bins_mnt/tmp/repo

# Copy host libs to chroot, required
cp -r /lib/x86_64-linux-gnu/ bins_mnt/lib/
cp -r /lib64/ bins_mnt/

cat <<EOF > bins_mnt/tmp/exclude
R /
- /dev
- /lib
- /lib64
- /lost+found
- /root/.ash_history
- /root/.cache
- /root/.config/borg
- /tmp
EOF

#epoch=$(date +@%s -d "$(basename "$i" | sed -re "s/.* ([0-9-]+)_([0-9]+)'([0-9]+)'([0-9]+)\..*/\1 \2:\3:\4/")")
#utcdate=$(date -u +%Y-%m-%dT%H:%M:%S -d @$(stat -c %Y "$i"))
#date=$(date +"%Y-%m-%d_%H:%M:%S" -d $epoch)
#gunzip -k my_tar.tgz

python3 ratarmount.py -c my_tar.tar archive_mnt/
mount.mergerfs archive_mnt/:bins_mnt/ mnt
mount --bind /dev mnt/dev

echo "backup"
chroot mnt/ /tmp/borg create --show-version --show-rc --verbose --list --stats --one-file-system --exclude-nodump --exclude-caches --keep-exclude-tags --patterns-from /tmp/exclude "/tmp/repo/::archive_name" 2>&1 | tee "logs/archive_name.log"

echo "backup dump"
zcat archive_mnt/dump.gz | bins_mnt/tmp/borg create --show-version --show-rc --verbose --list --stats --stdin-name dump "bins_mnt/tmp/repo/::archive_name_dump" - 2>&1 | tee "logs/archive_name_dump.log"

echo "unmount"
umount mnt/dev
umount mnt
umount archive_mnt/

#rm -f my_tar.tar

links.txt

https://borgbackup.readthedocs.io/en/stable/usage/create.html
https://borgbackup.readthedocs.io/en/stable/usage/help.html
https://superuser.com/questions/265772/is-it-possible-to-mount-a-tar-file
https://github.com/mxmlnkn/ratarmount
https://github.com/cybernoid/archivemount/
https://sebsauvage.net/wiki/doku.php?id=borgbackup

unix fake chroot
https://unix.stackexchange.com/questions/125680/different-fakechroot-behavior-on-fedora-and-ubuntu
https://unix.stackexchange.com/questions/66084/simulate-chroot-with-unshare
https://unix.stackexchange.com/questions/321361/how-do-i-when-running-an-executable-script-fake-the-root-directory
https://manpages.debian.org/wheezy/fakechroot/fakechroot.1
https://manpages.debian.org/testing/fakechroot/fakechroot.1.en.html

https://www.busybox.net/downloads/binaries/1.30.0-i686/
https://unix.stackexchange.com/questions/120015/how-to-find-out-the-dynamic-libraries-executables-loads-when-run
static libc
http://stevehanov.ca/blog/?id=97
static executable "not found"
https://amir.rachum.com/blog/2016/09/17/shared-libraries/
https://github.com/gflags/gflags/issues/283
https://unix.stackexchange.com/questions/476971/ldd-shows-no-location-after-arrow-library-does-not-exist-on-system
"_rmtree_safe_fd" FileNotFoundError: [Errno 2] No such file or directory: 'config'
-> syscall not implemented in fuse
ls: Value too large for defined data type
https://github.com/GoogleContainerTools/distroless/issues/225

https://unix.stackexchange.com/questions/227312/how-can-i-convert-a-local-date-time-into-utc-date-time
https://intoli.com/blog/exit-on-errors-in-bash-scripts/
archivemount : peut modifier les fichiers, gz, lent
ratarmount: rapide, bug si pas -c, pas gz