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:-$PKGDATADIR_DEFAULT}"
  25
  26 # shellcheck source=src/sh/dpkg-error.sh
  27 . "$PKGDATADIR/sh/dpkg-error.sh"
  28
  29 setup_colors
  30
  31 while [ $# -ne 0 ]; do
  32   case "$1" in
  33   --rotate=*)
  34     ROTATE="${1#--rotate=}"
  35     ;;
  36   esac
  37   shift
  38 done
  39
  40 # Check for required commands availability.
  41 for cmd in tar savelog; do
  42   if ! command -v $cmd >/dev/null; then
  43     error "cannot find required program '$cmd'"
  44   fi
  45 done
  46
  47 dbdir="$ADMINDIR"
  48
  49 # Backup the N last versions of dpkg databases containing user data.
  50 if cd $BACKUPSDIR ; then
  51   # We backup all relevant database files if any has changed, so that
  52   # the rotation number always contains an internally consistent set.
  53   dbchanged=no
  54   dbfiles="arch status diversions statoverride"
  55   for db in $dbfiles ; do
  56     if ! [ -s "dpkg.${db}.0" ] && ! [ -s "$dbdir/$db" ]; then
  57       # Special case the files not existing or being empty as being equal.
  58       continue
  59     elif ! cmp -s "dpkg.${db}.0" "$dbdir/$db"; then
  60       dbchanged=yes
  61       break
  62     fi
  63   done
  64   if [ "$dbchanged" = "yes" ] ; then
  65     for db in $dbfiles ; do
  66       if [ -e "$dbdir/$db" ]; then
  67         cp -p "$dbdir/$db" "dpkg.$db"
  68       else
  69         touch "dpkg.$db"
  70       fi
  71       savelog -c "$ROTATE" "dpkg.$db" >/dev/null
  72     done
  73   fi
  74
  75   # The alternatives database is independent from the dpkg database.
  76   dbalt=alternatives
  77
  78   # XXX: Ideally we'd use --warning=none instead of discarding stderr, but
  79   # as of GNU tar 1.27.1, it does not seem to work reliably (see #749307).
  80   if ! test -e ${dbalt}.tar.0 ||
  81      ! tar -df ${dbalt}.tar.0 -C $dbdir $dbalt >/dev/null 2>&1 ;
  82   then
  83     tar -cf ${dbalt}.tar -C $dbdir $dbalt >/dev/null 2>&1
  84     savelog -c "$ROTATE" ${dbalt}.tar >/dev/null
  85   fi
  86 fi