1 files changed, 87 insertions, 0 deletions
diff --git a/src/dpkg-db-backup.sh b/src/dpkg-db-backup.sh
new file mode 100755
index 0000000..619f489
--- /dev/null
+++ b/src/dpkg-db-backup.sh
@@ -0,0 +1,87 @@
+#!/bin/sh
+#
+# Copyright © 2014, 2017-2018, 2020-2021 Guillem Jover <guillem@debian.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+PROGNAME=$(basename "$0")
+ADMINDIR=/var/lib/dpkg
+BACKUPSDIR=/var/backups
+ROTATE=7
+
+PKGDATADIR_DEFAULT=src
+PKGDATADIR="${DPKG_DATADIR:-$PKGDATADIR_DEFAULT}"
+TAR="${TAR:-tar}"
+
+# shellcheck source=src/sh/dpkg-error.sh
+. "$PKGDATADIR/sh/dpkg-error.sh"
+
+setup_colors
+
+while [ $# -ne 0 ]; do
+  case "$1" in
+  --rotate=*)
+    ROTATE="${1#--rotate=}"
+    ;;
+  esac
+  shift
+done
+
+# Check for required commands availability.
+for cmd in "$TAR" savelog; do
+  if ! command -v "$cmd" >/dev/null; then
+    error "cannot find required program '$cmd'"
+  fi
+done
+
+dbdir="$ADMINDIR"
+
+# Backup the N last versions of dpkg databases containing user data.
+if cd $BACKUPSDIR ; then
+  # We backup all relevant database files if any has changed, so that
+  # the rotation number always contains an internally consistent set.
+  dbchanged=no
+  dbfiles="arch status diversions statoverride"
+  for db in $dbfiles ; do
+    if ! [ -s "dpkg.${db}.0" ] && ! [ -s "$dbdir/$db" ]; then
+      # Special case the files not existing or being empty as being equal.
+      continue
+    elif ! cmp -s "dpkg.${db}.0" "$dbdir/$db"; then
+      dbchanged=yes
+      break
+    fi
+  done
+  if [ "$dbchanged" = "yes" ] ; then
+    for db in $dbfiles ; do
+      if [ -e "$dbdir/$db" ]; then
+        cp -p "$dbdir/$db" "dpkg.$db"
+      else
+        touch "dpkg.$db"
+      fi
+      savelog -c "$ROTATE" "dpkg.$db" >/dev/null
+    done
+  fi
+
+  # The alternatives database is independent from the dpkg database.
+  dbalt=alternatives
+
+  # XXX: Ideally we'd use --warning=none instead of discarding stderr, but
+  # as of GNU tar 1.27.1, it does not seem to work reliably (see #749307).
+  if ! test -e ${dbalt}.tar.0 ||
+     ! $TAR -df ${dbalt}.tar.0 -C $dbdir $dbalt >/dev/null 2>&1 ;
+  then
+    $TAR -cf ${dbalt}.tar -C $dbdir $dbalt >/dev/null 2>&1
+    savelog -c "$ROTATE" ${dbalt}.tar >/dev/null
+  fi
+fi