Add backup script

Signed-off-by: Nikolaos Karaolidis <nick@karaolidis.com>

hosts/common/configs/system/backup/backup.completion.zsh

@@ -0,0 +1,16 @@
+_backup_completion() {
+  local options=(
+    '-m[specify partition to mount for backup]:partition:($(_partitions))'
+    '-b[specify backup directory]:backup directory:_files -/'
+  )
+  local curcontext="$curcontext" state line
+  typeset -A opt_args
+
+  _partitions() {
+    lsblk -rno NAME | sed 's/^/\/dev\//'
+  }
+
+  _arguments -s $options
+}
+
+compdef _backup_completion backup

hosts/common/configs/system/backup/backup.sh

@@ -0,0 +1,64 @@
+if [[ "${EUID}" -ne 0 ]]; then
+  echo "Please run the script as root."
+  exit 1
+fi
+
+usage() {
+  echo "Usage: $0 [-m partition] [-b backup_location]"
+  exit 1
+}
+
+cleanup() {
+  if [ -d "/persist.bak" ]; then btrfs -q subvolume delete "/persist.bak"; fi
+  if [ -n "${backup_location}" ] && [ -f "${backup_location}.tmp" ]; then rm "${backup_location}.tmp"; fi
+
+  if [ -n "${mount_location}" ]; then
+    if mount | grep -q "${mount_location}"; then umount "${mount_location}"; fi
+    if [ -d "${mount_location}" ]; then rmdir "${mount_location}"; fi
+  fi
+}
+
+partition=""
+backup_location=""
+mount_location=""
+
+trap cleanup EXIT
+
+while getopts "m:b:" opt; do
+  case "${opt}" in
+    m) partition="${OPTARG}" ;;
+    b) backup_location="${OPTARG}" ;;
+    *) usage ;;
+  esac
+done
+
+if [ -n "${partition}" ]; then
+  mount_location=$(mktemp -d /mnt/backup.XXXXXX)
+  echo "Mounting ${partition} at ${mount_location}..."
+  mount "${partition}" "${mount_location}"
+fi
+
+if [ -z "${mount_location}" ]; then
+  if [[ "${backup_location}" != /* ]]; then
+    backup_location="$(realpath "${backup_location}")"
+  fi
+else
+  if [[ "${backup_location}" = /* ]]; then
+    echo "Error: When a partition is mounted, backup_location must be relative."
+    exit 1
+  fi
+
+  backup_location="$(realpath "${mount_location}/${backup_location}")"
+fi
+
+backup_location="${backup_location}/$(hostname)-$(date +%Y-%m-%d-%H-%M-%S).btrfs.gz"
+
+echo "Creating /persist snapshot..."
+btrfs -q subvolume snapshot -r "/persist" "/persist.bak"
+
+echo "Creating backup at ${backup_location}..."
+btrfs -q send "/persist.bak" | gzip > "${backup_location}.tmp"
+
+mv "${backup_location}.tmp" "${backup_location}"
+
+echo "Backup completed successfully!"

hosts/common/configs/system/backup/default.nix

@@ -0,0 +1,20 @@
+{ pkgs, ... }:
+{
+  environment.systemPackages = [
+    (pkgs.writeShellApplication {
+      name = "backup";
+      runtimeInputs = with pkgs; [
+        btrfs-progs
+        coreutils-full
+        util-linux
+      ];
+      text = builtins.readFile ./backup.sh;
+    })
+  ];
+
+  home-manager.sharedModules = [
+    {
+      programs.zsh.initExtra = builtins.readFile ./backup.completion.zsh;
+    }
+  ];
+}