Add borg system backup script

config/system_backup.EXAMPLE

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+BORG_PASSPHRASE="some.random.strong.password.here"
+MOUNTPOINT=/mnt/backup_disk
+

system_backup.sh

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+#!/bin/bash
+
+#
+# Script configuration
+#
+
+script_dir=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
+set -o allexport
+source ${script_dir}/config/system_backup
+set +o allexport
+
+export BORG_REPO=$MOUNTPOINT/borg/backups
+
+DATE=$(date -u +%Y-%m-%d-%H-%M)
+
+
+#
+# Create backups
+#
+
+# Options for borg create
+BORG_OPTS="--stats --compression lz4 --one-file-system --checkpoint-interval 86400"
+
+# No one can answer if Borg asks these questions, it is better to just fail quickly
+# instead of hanging.
+export BORG_RELOCATED_REPO_ACCESS_IS_OK=no
+export BORG_UNKNOWN_UNENCRYPTED_REPO_ACCESS_IS_OK=no
+
+# some helpers and error handling:
+info() { printf "\n%s %s\n\n" "$( date )" "$*" >&2; }
+trap 'echo $( date ) Backup interrupted >&2; exit 2' INT TERM
+
+borg --version
+
+info "Starting backup for $DATE"
+
+borg create $BORG_OPTS        \
+  --verbose                   \
+  --filter AME                \
+  --list                      \
+  --stats                     \
+  --show-rc                   \
+  --compression lz4           \
+  --exclude-caches            \
+  --exclude 'root/.cache'     \
+  --exclude 'home/*/.cache/*' \
+  --exclude 'var/tmp/*'       \
+  ::'{hostname}-debian-{now}' \
+  /home /root /etc /var
+
+backup_exit=$?
+
+
+info "Pruning repository"
+
+borg prune                                 \
+    --list                                 \
+    --glob-archives '{hostname}-debian-*'  \
+    --show-rc                              \
+    --keep-daily    7                      \
+    --keep-weekly   4                      \
+    --keep-monthly  6
+
+prune_exit_1=$?
+
+borg prune                                 \
+    --list                                 \
+    --glob-archives '{hostname}-trident-*' \
+    --show-rc                              \
+    --keep-daily    7                      \
+    --keep-weekly   4                      \
+    --keep-monthly  6
+
+prune_exit_2=$?
+prune_exit=$(( prune_exit_2 > prune_exit_1 ? prune_exit_2 : prune_exit_1 ))
+
+
+info "Compacting repository"
+
+borg compact
+
+compact_exit=$?
+
+
+# use highest exit code as global exit code
+global_exit=$(( backup_exit > prune_exit ? backup_exit : prune_exit ))
+global_exit=$(( compact_exit > global_exit ? compact_exit : global_exit ))
+
+if [ ${global_exit} -eq 0 ]; then
+    info "Backup, Prune, and Compact finished successfully"
+elif [ ${global_exit} -eq 1 ]; then
+    info "Backup, Prune, and/or Compact finished with warnings"
+else
+    info "Backup, Prune, and/or Compact finished with errors"
+fi
+
+exit ${global_exit}