src/dpkg-db-backup.sh

   1 #!/bin/sh
   2 #
   3 # Copyright © 2014, 2017-2018, 2020-2021 Guillem Jover <guillem@debian.org>
   4 #
   5 # This program is free software; you can redistribute it and/or modify
   6 # it under the terms of the GNU General Public License as published by
   7 # the Free Software Foundation; either version 2 of the License, or
   8 # (at your option) any later version.
   9 #
  10 # This program is distributed in the hope that it will be useful,
  11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 # GNU General Public License for more details.
  14 #
  15 # You should have received a copy of the GNU General Public License
  16 # along with this program.  If not, see <https://www.gnu.org/licenses/>.
  17
  18 PROGNAME=$(basename "$0")
  19 ADMINDIR=/var/lib/dpkg
  20 BACKUPSDIR=/var/backups
  21 ROTATE=7
  22
  23 PKGDATADIR_DEFAULT=src
  24 PKGDATADIR="${DPKG_DATADIR:-$PKGDATADIR_DEFAULT}"
  25 TAR="${TAR:-tar}"
  26
  27 # shellcheck source=src/sh/dpkg-error.sh
  28 . "$PKGDATADIR/sh/dpkg-error.sh"
  29
  30 setup_colors
  31
  32 while [ $# -ne 0 ]; do
  33   case "$1" in
  34   --rotate=*)
  35     ROTATE="${1#--rotate=}"
  36     ;;
  37   esac
  38   shift
  39 done
  40
  41 # Check for required commands availability.
  42 for cmd in "$TAR" savelog; do
  43   if ! command -v "$cmd" >/dev/null; then
  44     error "cannot find required program '$cmd'"
  45   fi
  46 done
  47
  48 dbdir="$ADMINDIR"
  49
  50 # Backup the N last versions of dpkg databases containing user data.
  51 if cd $BACKUPSDIR ; then
  52   # We backup all relevant database files if any has changed, so that
  53   # the rotation number always contains an internally consistent set.
  54   dbchanged=no
  55   dbfiles="arch status diversions statoverride"
  56   for db in $dbfiles ; do
  57     if ! [ -s "dpkg.${db}.0" ] && ! [ -s "$dbdir/$db" ]; then
  58       # Special case the files not existing or being empty as being equal.
  59       continue
  60     elif ! cmp -s "dpkg.${db}.0" "$dbdir/$db"; then
  61       dbchanged=yes
  62       break
  63     fi
  64   done
  65   if [ "$dbchanged" = "yes" ] ; then
  66     for db in $dbfiles ; do
  67       if [ -e "$dbdir/$db" ]; then
  68         cp -p "$dbdir/$db" "dpkg.$db"
  69       else
  70         touch "dpkg.$db"
  71       fi
  72       savelog -c "$ROTATE" "dpkg.$db" >/dev/null
  73     done
  74   fi
  75
  76   # The alternatives database is independent from the dpkg database.
  77   dbalt=alternatives
  78
  79   # XXX: Ideally we'd use --warning=none instead of discarding stderr, but
  80   # as of GNU tar 1.27.1, it does not seem to work reliably (see #749307).
  81   if ! test -e ${dbalt}.tar.0 ||
  82      ! $TAR -df ${dbalt}.tar.0 -C $dbdir $dbalt >/dev/null 2>&1 ;
  83   then
  84     $TAR -cf ${dbalt}.tar -C $dbdir $dbalt >/dev/null 2>&1
  85     savelog -c "$ROTATE" ${dbalt}.tar >/dev/null
  86   fi
  87 fi