Backup crontabs on Yunohost

YunoHost usually already knows what needs to be backed up. However, if you have made manual changes, such as installing an app outside of the YunoHost application system, you may want to extend YunoHost’s mechanism to specify other files to be backed up.

I use borg as the backup method and after checking the archives (prefixed with _auto_conf and _auto_data) I found the crontab files are not included.

After reading the official document, here’s what I managed to do to backup them.

Steps

Two hook files are all we need, this will work for backup methods other than borg too.

What will be included in the backup:

• /var/spool/cron/crontabs the crontab -l for *every user
• The two hook files

Caution:

1. Do everything with root.
2. If you change the name of the hook files, adjust the file content accordinly.

Create folders for hooks

mkdir -p /etc/yunohost/hooks.d/{backup,restore}

Create the backup hook

/etc/yunohost/hooks.d/backup/99-conf_custom

Content

#!/bin/bash

# Source YNH helpers
source /usr/share/yunohost/helpers

ynh_restore_dest (){
    YNH_CWD="${YNH_BACKUP_DIR%/}/$1"
    cd "$YNH_CWD"
}


# Exit hook on subcommand error or unset variable
ynh_abort_if_errors

# Crontabs
ynh_restore_dest "conf/custom/crontabs"
ynh_restore_file "/var/spool/cron/crontabs"

# MISC (including this file)
ynh_restore_dest "conf/custom/misc"
ynh_restore_file "/etc/yunohost/hooks.d/backup/99-conf_custom"
ynh_restore_file "/etc/yunohost/hooks.d/restore/99-conf_custom"

Create the restore hook

/etc/yunohost/hooks.d/restore/99-conf_custom

Content

#!/bin/bash

# Source YNH helpers
source /usr/share/yunohost/helpers

ynh_backup_dest (){
    YNH_CWD="${YNH_BACKUP_DIR%/}/$1"
    mkdir -p $YNH_CWD
    cd "$YNH_CWD"
}

# Exit hook on subcommand error or unset variable
ynh_abort_if_errors

# Crontabs
ynh_backup_dest "conf/custom/crontabs"
ynh_backup "/var/spool/cron/crontabs"

# MISC (including this file)
ynh_backup_dest "conf/custom/misc"
ynh_backup "/etc/yunohost/hooks.d/backup/99-conf_custom"
ynh_backup "/etc/yunohost/hooks.d/restore/99-conf_custom"

Assign proper file permissions

This might not be necessary, but I did it just in case.

chmod 740 /etc/yunohost/hooks.d/{backup,restore}/99-conf_custom

Fire up a backup to see if the hook works

For borg, to start a backup is as easy as systemctl start borg

The files will be included in the archive with the prefix _auto_conf, this will list the files in the ARCHIVE_NAME:

app=borg; BORG_PASSPHRASE="$(yunohost app setting $app passphrase)" BORG_RSH="ssh -i /root/.ssh/id_${app}_CHANGE_THIS -oStrictHostKeyChecking=yes " borg list "$(yunohost app setting $app repository)::ARCHIVE_NAME | grep crontabs"