From 8005557061c0e795be334d47ae8f6669ecf4ab8c Mon Sep 17 00:00:00 2001 From: Slavi Pantaleev Date: Mon, 5 Dec 2022 15:28:07 +0200 Subject: [PATCH] Give backup-borg container more permissions to perform the backup Running with a user (like `matrix:matrix`) fails if Etherpad is enabled, because `/matrix/etherpad` is owned by `matrix_etherpad_user_uid`/`matrix_etherpad_user_gid` (`5001:5001`). The `matrix` user can't acccess the Etherpad directory for this reason and Borgmatic fails when trying to make a backup. There may be other things under `/matrix` which similarly use non-`matrix:matrix` permissions. Another workaround might have been to add `/matrix/etherpad` (and potentially other things) to `matrix_backup_borg_location_exclude_patterns`, but: - that means Etherpad won't be backed up - not great - only excluding Etherpad may not be enough. There may be other files we need to exclude as well --- Running with `root` is still not enough though. We need at least the `CAP_DAC_OVERRIDE` capability, or we won't be able to read the `/etc/borgmatic.d/config.yaml` configuration file (owned by `matrix:matrix` with `0640` permissions). --- Additionally, it seems like the backup process tries to write to at least a few directories: - `/root/.borgmatic` - `/root/.ssh` - `/root/.config` > [Errno 30] Read-only file system: '/root/.borgmatic' > Error while creating a backup. > /etc/borgmatic.d/config.yaml: Error running configuration file We either need to stop mounting the container filesystem as readonly (remove `--read-only`) or to allow writing via a `tmpfs`. I've gone the `tmpfs` route which seems to work. In any case, the mounted source directories (`matrix_backup_borg_location_source_directories`) are read-only regardless, so our actual source files are protected from unintentional changes. --- .../templates/systemd/matrix-backup-borg.service.j2 | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/roles/custom/matrix-backup-borg/templates/systemd/matrix-backup-borg.service.j2 b/roles/custom/matrix-backup-borg/templates/systemd/matrix-backup-borg.service.j2 index 8048c2e4..760fd574 100644 --- a/roles/custom/matrix-backup-borg/templates/systemd/matrix-backup-borg.service.j2 +++ b/roles/custom/matrix-backup-borg/templates/systemd/matrix-backup-borg.service.j2 @@ -33,12 +33,16 @@ ExecStartPre=-{{ devture_systemd_docker_base_host_command_docker }} run --rm --n {{ matrix_backup_borg_docker_image }} \ sh -c "borgmatic rcreate --encryption {{ matrix_backup_borg_encryption }}" +# The `CAP_DAC_OVERRIDE` capability is required, so that `root` in the container +# can read the `/etc/borgmatic.d/config.yaml` (`{{ matrix_backup_borg_config_path }}/config.yaml`) file, +# owned by `matrix:matrix` on the filesystem. ExecStart={{ devture_systemd_docker_base_host_command_docker }} run --rm --name matrix-backup-borg \ --log-driver=none \ --cap-drop=ALL \ + --cap-add=CAP_DAC_OVERRIDE \ --read-only \ - --user={{ matrix_user_uid }}:{{ matrix_user_gid }} \ --network={{ matrix_docker_network }} \ + --tmpfs=/root:rw,noexec,nosuid,size=100m \ --tmpfs=/tmp:rw,noexec,nosuid,size=100m \ --mount type=bind,src={{ matrix_backup_borg_config_path }}/passwd,dst=/etc/passwd,ro \ --mount type=bind,src={{ matrix_backup_borg_config_path }},dst=/etc/borgmatic.d,ro \