include backup functionality

system/backup

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+#!/bin/bash
+#
+# Purpose : Back up your home folder with borg to your Nextcloud files, in
+#           /mnt/<domain>/.backup-<hostname>. Run daily by
+#           coredesktop-backup.timer; `configure backup` sets it up.
+#
+# Keeps 7 daily, 4 weekly and 6 monthly backups. To leave out more, list
+# paths or borg patterns in ~/.config/coredesktop/backup-exclude, one per line.
+
+# Wrapped in { ...; exit; } so bash reads the whole script up front; update
+# replaces this file (git pull) while a backup may be running.
+{
+
+BACKUP_CONF="$HOME/.config/coredesktop/backup.conf"
+USER_EXCLUDE="$HOME/.config/coredesktop/backup-exclude"
+
+# Tell the desktop when a backup fails, as no one watches the timer
+fail() {
+  echo "$1" >&2
+  notify-send --app-name=CoreDesktop --icon=dialog-error "Backup failed" "$1" 2> /dev/null
+  exit 1
+}
+
+[ -f "$BACKUP_CONF" ] || fail "Backups aren't set up. Run: configure backup"
+source "$BACKUP_CONF"
+
+# The files mount comes up at login, perhaps before the network; give it a
+# few minutes rather than writing into the empty folder underneath
+for try in {1..10}; do
+  mountpoint -q "$BACKUP_MOUNT" && break
+  mount "$BACKUP_MOUNT" 2> /dev/null && break
+  sleep 30
+done
+mountpoint -q "$BACKUP_MOUNT" || fail "Your Nextcloud files aren't mounted at $BACKUP_MOUNT."
+
+export BORG_REPO
+export BORG_PASSCOMMAND="secret-tool lookup coredesktop backup repo $BORG_REPO"
+
+# Rebuilt by borg, or by reinstalling, so not worth the space
+excludes=(
+  "$HOME/.cache"
+  "$HOME/.davfs2/cache"
+  "$HOME/.local/share/Trash"
+  "$HOME/.local/share/containers"
+  "$HOME/.local/share/flatpak"
+  "$HOME/.local/share/siblings"
+  "$HOME/.local/share/coredesktop"
+  "$HOME/.var/app/*/cache"
+  "$HOME/.npm"
+  "$HOME/.cargo/registry"
+  "$HOME/go/pkg/mod"
+)
+exclude_args=(--exclude-caches)
+for path in "${excludes[@]}"; do
+  exclude_args+=(--exclude "sh:$path")
+done
+[ -f "$USER_EXCLUDE" ] && exclude_args+=(--exclude-from "$USER_EXCLUDE")
+
+echo "Backing up $HOME to $BORG_REPO..."
+# --one-file-system leaves out other mounts and btrfs subvolumes inside home
+borg create --one-file-system --compression zstd --stats \
+  "${exclude_args[@]}" "::{hostname}-{now:%Y-%m-%dT%H:%M}" "$HOME"
+status=$?
+# 1 is a warning, e.g. a file changed while it was read; the backup still exists
+(( status <= 1 )) || fail "borg couldn't back up $HOME (exit $status). See: journalctl --user -u coredesktop-backup"
+
+echo "Removing old backups..."
+borg prune --glob-archives '{hostname}-*' \
+  --keep-daily 7 --keep-weekly 4 --keep-monthly 6 \
+  || fail "borg couldn't remove old backups. See: journalctl --user -u coredesktop-backup"
+borg compact || fail "borg couldn't free space from old backups. See: journalctl --user -u coredesktop-backup"
+
+echo "Backup finished."
+exit 0
+}

system/systemd/coredesktop-backup.service

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+[Unit]
+Description=Back up your home folder to your Nextcloud files
+
+[Service]
+Type=oneshot
+ExecStart=%h/.local/share/coredesktop/system/backup
+# Stay out of the way of whatever you're doing
+Nice=19
+IOSchedulingClass=idle

system/systemd/coredesktop-backup.timer

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+[Unit]
+Description=Back up your home folder daily
+
+[Timer]
+OnCalendar=daily
+RandomizedDelaySec=1h
+# Catch up at the next login if the computer was off or you weren't logged in
+Persistent=true
+
+[Install]
+WantedBy=timers.target