Man Linux: Main Page and Category List


       backup2l -  low-maintenance backup/restore tool


       backup2l [ -c conffile ] [ -t backup-ID ] command


       backup2l is a tool for generating, maintaining and restoring backups on
       a mountable file system (e. g. hard disk). The main  design  goals  are
       low  maintenance  effort,  efficiency, transparency and robustness.  It
       features differential  backups  at  multiple  hierarchical  levels  and
       provides rollback functionality.

       All  control  files are stored together with the archives on the backup
       device, and their contents are mostly self-explaining.  Hence,  in  the
       case  of an emergency, a user does not only have to rely on the restore
       functionality of backup2l, but can - if necessary -  browse  the  files
       and extract archives manually.

       An  open  driver  architecture  allows  to  use virtually any archiving
       program as a backend.  Built-in drivers support .tar.gz,  .tar.bz2,  or
       .afioz  files. Further drivers can be added by the user. When restoring
       data, an appropriate driver is selected automatically for each  archive
       depending on the suffix of the archive file.

       The  method of hierarchical differential backups is a generalization to
       the concept of the  "daily",  "weekly"  and  "monthly"  backups.   Each
       backup  has  a  level  and  a  serial number. Maximum-level backups are
       comparable with daily differential backups, level-0  backups  are  full
       backups.  For example, let MAX_LEVEL be 4 and MAX_PER_LEVEL be 5. After
       5 level-4 backups (e. g. after 5 days), a new level-3 backup  is  made.
       After  5  level-3 backups (and 5*5 at level-4), a new level-2 backup is
       made, and so on.  Each differential backup contains the changes towards
       the previous backup of the same or a lower level.

       This scheme allows to efficiently generate small incremental backups at
       short intervals.  At the same time, the total number of  archives  that
       have  to  be  stored  (or  processed  in  the  case  of a restore) only
       increases logarithmically with the number of  backups  since  the  last
       full  backup. Time-consuming full backups are only sparsely needed.  In
       the example above, a new  full  backup  is  only  necessary  after  780
       (=5^4+5^3+5*5+5) days, while only at most 20 (=4*5) archives have to be

       For backup2l, each backup archive is identified by its backup ID (BID).
       The  number of digits determines the level. Level-0 (full) backups have
       a 1-digit BID, level-n backups have a BID  of  n+1  digits.   The  last
       digit is a serial number, the prefix identifies the lower-level backups
       on which a given backup is based  on.  For  example,  the  archive  235
       contains  the  differences towards archive 234, and to restore the file
       system state of the time it was  generated,  the  full  backup  2,  the
       level-1  backups  21, 22, 23 and the level-2 backups 231, ..., 235 have
       to be processed.  All serial numbers are between 1 and 9, a zero in the
       BID  indicates  that no archive of the respective level is contained in
       the chain. For example, the level-3 backup 1201 is immediately based on
       the level-1 backup 12.

       For  deciding  whether a file is new or modified, backup2l looks at its
       name, modification time, size, ownership and permissions. Unlike  other
       backup  tools,  the i-node is not considered in order to avoid problems
       with non-Unix file systems like FAT32.


       -c, --conf conffile
              This  argument  specifies  the  configuration   file   (default:

       -t, --time BID
              If  present,  this  option  selects  a  certain  backup  for the
              --locate and --restore commands.  E. g., the latter will restore
              files  and directories exactly as they were on the system at the
              time when the specified backup was made.  If  not  present,  the
              latest available backup is selected.


       -h, --help
              Display the usage info.

       -e, --estimate [ level ]
              Prints  the  number of files, estimated amount of data and other
              information on the backup  that  would  be  generated  next.  No
              backup  archives  are actually created or removed. If specified,
              the parameter level overrides the MAX_LEVEL setting.

       -b, --backup [ level ]
              Creates a new backup and removes old archives based on the given
              configuration file.  If specified, the parameter level overrides
              the MAX_LEVEL setting. This is useful e. g.  shortly  before  or
              after  major changes are performed with the file system. In this
              case, a lower level should be specified in order to avoid that a
              large number of files are backed up multiple times again.

       -s, --get-summary
              Shows  a  table  describing each backup (date, size, files, ...)
              and the file system usage of the backup device.

       -a, --get-available [ pattern list ]
              Shows all files removed and added for all backups. A ’+’ in  the
              output  indicates that the file is new and thus contained in the
              archive file. A ’-’ indicates that the file has been removed (or
              replaced).   If one or several patterns are supplied, grep(1) is
              used to filter the list. All status messages go  to  stderr,  so
              that the generated file list can easily be redirected.

              Note:  The search pattern is not just applied to the file names,
              but to the whole entry in the .list.gz file. This allows you  to
              not  only  search  for  file names but also for other attributes
              like ownership, modification time etc. . In  order  to  apply  a
              search pattern to file names only, precede it by "<space>/.*".

       -l, --locate [ pattern list ]
              Shows  most  recent  backup location for active files. If one or
              several patterns are supplied, grep(1) is  used  to  filter  the
              list  in  the  same way as for --get-available (see above) . All
              status messages go to stderr, so that the  generated  file  list
              can easily be redirected.

              Active  files are files that have been on the system at the time
              of the selected backup, which is either the latest backup or the
              one  specified by --time (see above). Files that were removed at
              that time but are still stored in some later archive will not be

              Altogether,  this  command  tells  you,  which  files have to be
              extracted from which archive in order to restore  the  state  of
              the system at the time of the selected backup.

       -r, --restore [ pattern list ]
              Performs  the  same  steps  like  --locate and then restores the
              respective files. All files are restored relative to the current
              directory.  They  can  be restored to their original location by
              cd’ing into / before, but this is not recommended.

       -p, --purge BID list
              Removes  the  specified  backup  archive(s)  and  all  depending

       -m, --make-check [ BID list ]
              Creates  (a)  check  file(s)  for the specified archive(s) using
              md5sum(1).  If no BID is  specified,  check  files  are  created
              wherever missing.

       -v, --verify [ BID list ]
              Verifies   the   specified  backup  archive(s).  If  no  BID  is
              specified, all existing archives are checked.  If a  check  file
              exists,  this  allows a comprehensive test including e. g. media
              failures. If the check file is missing, only  the  existence  of
              all files and the immediate base archive are verified.

       -x, --extract capacity max-free BID-list
              Split  and  collect files to be stored on removable media (e. g.
              CDs). capacity is the medium capacity in  MB.  max-free  is  the
              maximum  amount  of  empty  space on each medium (except for the
              last one, of course). BID-list specifies the  archives  and  may
              contain  wildcards,  e.  g.:  1  ’2*’.   The operation generates
              enumbered subdirectories representing the media contents.   Some
              more  files  are  generated  that  may be useful, e. g. to print

              While guaranteeing a minimum waste of max-free  MB  per  medium,
              the  collection  procedure  preserves  the ordering of files and
              keeps all control files of an archive  always  together  on  the
              same  medium.  Large archive files are split into multiple files
              with serial numbers appended to their names.

              The operation is interactive. Just run it and look  what  it  is
              about to do.  If that is not what you want, you can stop it.


       In   the   configuration  file  (/etc/backup2l.conf  by  default),  the
       following variables have to be set, following the bash(1) syntax:

              Defines the backup2l version for which the configuration file is
              written.  This  way,  future  versions can automatically print a
              warning if the syntax has changed.

       SRCLIST=( source list )
              This is a blank-separated list of all top-level  directories  to
              make backups of.  Directory names with spaces have to be quoted,
              e. g.: SRCLIST=("/my dir" /another/dir).  The last  elements  of
              the  list may be options for find(1), for example -xdev in order
              to skip subdirs on other file systems like /dev or /proc.

       SKIPCOND=( find condition )
              Files for which this condition is ’true’ are not considered  for
              backup.   See  find(1)  for  information  on  how  to  formulate
              possible conditions.  Special characters ("(",  ")",  "!",  ...)
              must  be quoted by a leading backslash ("\(", "\)", " \!", ...).
              An empty condition (i. e. if you do not want  any  files  to  be
              skipped) must be specified as "( -false )".

       [ BACKUP_DEV="mount_point" ]
              If  defined,  backup2l  mounts  the  backup  device  before  any
              operation.  Afterwards, it is unmounted unless  it  was  already
              mounted before.

       BACKUP_DIR="backup dir"
              Destination  directory  for backup files. This must be different
              from MOUNT_POINT, i. e.  a subdirectory on the device.

              This is a common  prefix  for  all  backup  and  control  files.
              Multiple  backup  volumes  are  possible  if  for  each volume a
              separate configuration file is written.

              Maximum backup level. Possible values are 1..9.

              Number of differential backups per level.  Possible  values  are

              Number of full backups kept. Possible values are 1..8.

              Number  of  backup  generations to keep for each non-zero level.
              Old backups are  automatically  removed  as  long  as  at  least
              GENERATIONS  *  MAX_PER_LEVEL  backups  for the respective level

              For example, with MAX_LEVEL=3, MAX_PER_LEVEL=5, GENERATIONS=2 it
              is  always  possible to access the last 10 level-3 (e. g. daily)
              backups, the last 10 level-2 backups (e. g. 5, 10, 15,  ...,  50
              days old), and so on.

       PRE_BACKUP () { do something }
              This  function  is  called  before writing the backup. It can be
              used to dump some important system information, e. g.  the  HD’s
              partition table, to a file which is then backed up.

       POST_BACKUP () { do something }
              This  function is called after writing the backup. Together with
              PRE_BACKUP it can be used to stop and restart e. g. database  or
              mail services which may frequently alter some files that have to
              be backed up.

       [ AUTORUN=1 ]
              If set to 1,  backup2l  performs  the  --backup  operation  when
              invoked  without arguments.  Otherwise, the usage information is

       [ SIZE_UNITS= B | K | M | G ]
              Sets the units for archive sizes in summary listings  to  bytes,
              KB,  MB,  or  GB.   If  unset,  a user-readable format is chosen
              automatically. If set, the units are  the  same  for  the  whole
              table, which may be even more user-friendly.

       [ CREATE_DRIVER="archive driver" ]
              Selects  an  archive  driver  for  creating  backups. An archive
              driver is responsible for managing backup files. If  unset,  the
              default  driver  "DRIVER_TAR_GZ"  is  used. The --help operation
              lists all available drivers. More drivers can be defined in  the
              configuration file (see below).

       [ USER_DRIVER_LIST="user-defined drivers" ]
              Declares  additional,  user-defined  archive  drivers  which are
              implemented in the configuration file.  The sample configuration
              file contains a commented example. Read it in order to learn how
              to implement your own driver.


              Configuration file.

       VOLNAME.BID.tar.gz, VOLNAME.BID.afioz, ...
              Archive files.

              List of all active files when the backup was made. Each file  is
              preceded   with   its   size,   modification   time,  and  other
              List of all new ore modified files  when  the  backup  was  made
              (pathnames  only).  Unless  an error occured, this list reflects
              the contents of the archive.

              List of all obsolete files when the backup was  made  (pathnames

              Complete  list  of  all  files  that  were  skipped according to

              This file is generated by comparing the .new.gz  file  with  the
              actual  archive  contents  using  diff(1).  If the error file is
              non-empty, something may have gone wrong.

              MD5 check sums of all files  of  the  present  archive  and  the
              .list.gz  file  of  the base archive.  This file is optional and
              may be used by the --verify operation.


       backup2l is designed to be run autonomously as  a  cron  job.   If  the
       variable  AUTORUN  is set, it generates a backup if invoked without any
       parameters, and you can simply create a symlink, e. g. by:

                 ln -s ‘which backup2l‘ /etc/cron.daily/zz-backup2l

       The "zz-" prefix causes the backup job to be the last one executed,  so
       that  other  jobs  are not delayed if the backup takes somewhat longer.
       The status output is e-mailed to root by the cron daemon.


       backup2l has been designed to be robust  with  respect  to  errors  and
       configuration  changes.   If  the  backup process is interrupted, e. g.
       because of a shutdown while it is running, no serious  data  corruption
       can  occur. Some temporary files may remain which are cleaned up during
       the next run. If file is changed during the backup generation,  it  may
       not  be contained in the current backup. However, it is guaranteed that
       it is considered modified during the next backup.

       In order to save disk space, e. g. after some archives have been copied
       to  external  media, archive files (.tar.gz or .afioz, for example) can
       safely be removed from the backup directory.  As long  as  all  control
       files are kept, backup2l retains full functionality as far as possible.
       The --restore command prompts for eventually missing archive files  for
       the   respective  request  (and  only  those).  The  --extract  command
       completely ignores all backups with missing archive files.

       The   configuration,   especially   the   settings    for    MAX_LEVEL,
       MAX_PER_LEVEL,  MAX_FULL  and the specification of source files, can be
       arbitrarily changed without having to expect data corruption.  backup2l
       will gracefully adapt the new settings during the next run.


       After  a  restore  operation,  the  modification time of directories is
       equal to the restoration time while  for  files  it  is  equal  to  the
       original modification time.


       backup2l was written by Gundolf Kiefer <gundolfk at>.

       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
       General Public License for more details.


       tar(1), afio(1), find(1), grep(1), md5sum(1)