bakonf usermanual

Iustin Pop

   Copyright © 2002 Iustin Pop, <iusty@k1024.org>

   This document explains the concept and usage of bakonf 0.5.2, a
   system tool which backs up the configuration files on a system.
     __________________________________________________________

   Table of Contents
   1. About this document
   2. Introduction
   3. Quick start
   4. Details about bakonf

        4.1. Filesystem backup

              4.1.1. File types and states

        4.2. Metadata

              4.2.1. Partition table
              4.2.2. Device list

        4.3. What can I use bakonf for?
        4.4. Requirements

   5. Configuration

        5.1. Configuration language
        5.2. File list

   6. Using bakonf

        6.1. Backup phase
        6.2. Restore phase

              6.2.1. Configuration rollback
              6.2.2. Complete system restoration

1. About this document

   This is the usermanual for the bakonf project, version 0.5.2;
   homepage is at http://www.nongnu.org/bakonf/. You can also get
   new versions of this document there.
     __________________________________________________________

2. Introduction

   Making backup is an important aspect of system administration.
   The techniques of backing up data are explained in any good
   document about system administration, and they won't be
   explained here again.

   However, bakonf comes into play into a particular part of the
   backups: the backing up of the system's configuration.

   The basic idea is that on a standard installation of a
   Unix-like system you have a lot of data which can be very
   easily restored from the original media, thus there is no point
   in archiving it. For example, after a fresh install of a RedHat
   Linux 8.0, you have ˜4.5GB of space used. However, only a very
   small part of this amount is holding important information, the
   other part being binaries, libraries and other kind of data
   which will never modify in normal usage. Only the configuration
   files are changing (of course, also the user data is changing,
   but we are talking about an empty system).

   If we classify the files existing on a Unix system, we have:

   configuration data
          These are the target of bakonf; they are usually small
          text files, partly coming from the system installation,
          maybe edited by the administrator, partly created by
          him. Size is (on the workstation I write this) ˜15MB.

   binaries, libraries, other system files
          These are mostly read-only; in a package based
          distribution, they came from the packages and are
          replaced when the package is upgraded. In classical
          systems, they come from the install archives. Size is
          (in our hypothetical rh8.0 full install) ˜4.5GB.

   user data
          These are emails, web pages, documents, etc. - this is
          important data, and needs to be backed up regularly.
          They also don't come from the installation media, and
          are not touched by the system. Size is undetermined, but
          is guaranteed to be exactly the amount of free space on
          the system :).

   system variable data
          These are the files created and managed by the system,
          usually from the configuration files and other external
          variables. Examples: /var/lib/logrotate.status,
          /var/lib/slocate/slocate.db. These are not all critical
          files, some are needed to be included in a backup only
          for analysis purposes, others should not be included in
          backups (e.g. if you reinstall your system or restore
          from backup, some files will have for sure other
          contents, generated from the new installation).

   From all these, only the configuration data and the user data
   are absolutely required to recreate the system. The binaries
   can come from the installation source. The system managed data
   will be recreated by the system. And since the difference in
   size between the configuration and user data is so great in a
   typical system, I believe it deserves another backup method
   (besides the inclusion in standard backup procedures, which
   are, I repeat, CRITICAL!).
     __________________________________________________________

3. Quick start

    1. run bakonf with -L0 to archive all config files and create
       its database:
# bakonf -L0
#
       If everything went well, bakonf has created an archive
       under /var/lib/bakonf/archives named after your host. Look
       into that directory to find it. If any errors have
       occurred, bakonf will tell you:
[user@test user]$ bakonf -L0
Error: cannot read '/nfs/README': 'Permission denied'. Not archived.
Warning: '/sbin/lsusb -vv' exited with status 1.
Warning: '/sbin/sfdisk -d /dev/hda' exited with status 1.
[user@test user]$
    2. run daily (or more often) bakonf with -L1 to archive only
       the changed files since the previous step. This archive
       should be much smaller. It will be easy, after encryption,
       to email it.
# bakonf -L1
#
    3. every week, go back to the first step.
     __________________________________________________________

4. Details about bakonf

   bakonf home page is http://www.nongnu.org/bakonf/. The project
   is hosted at http://savannah.nongnu.org/projects/bakonf/.

   You can regard bakonf as a rescue archive creator. It creates
   an archive of configuration files and metadata information
   about the system. By metadata, I mean data which is not found
   anywhere in the filesystem as simple files: partition table
   layout, hardware configuration, kernel version, etc.

   Table 1. Archive layout
   Filename Description Created when
   README A file which contains informations about the archive:
   when it was generated, with which options and on what host
   Always
   unarchived_files.lst A file which contains details about which
   files couldn't be backed up; this can happen when bakonf is not
   run as root, or when it scans NFS directories When filesystem
   backup has been performed
   commands_with_errors.lst A file which contains details about
   which commands have exited with non-zero status. Their output
   is still stored in the archive, though. When metadata backup
   has been performed
   filesystem/ Under this path are stored the files backed up.
   When filesystem backup has been performed
   metadata/ Under this path are stored the files resulted from
   metadata backup. When metadata backup has been performed
     __________________________________________________________

4.1. Filesystem backup

   Bakonf can be operated in two modes: level 0, level 1. In level
   0, it archives all of the specified configuration files and
   registers the state of those configuration files in a database
   (called virtuals database), of type Berkley DB. In level 1, it
   archives only the files modified since the last level 0 backup;
   it does this by comparing the virtuals database with the
   filesystem.
     __________________________________________________________

4.1.1. File types and states

   Here is how bakonf treats files

   directories
          they won't be archived if they don't contain files to be
          backed up. On the other hand, for each file to be backed
          up, bakonf will also backup (non-recursively) its parent
          directories (except root) so that you have the user,
          group, mtime and permissions of each directory. For
          example, if /usr/local/etc/myconfig has been selected
          for archiving, bakonf will actually archive this list of
          items: /usr, /usr/local, /usr/local/etc,
          /usr/local/etc/myconfig.

   regular files
          regular files will be archived by bakonf if they aren't
          excluded by the noscan configuration directive. In case
          this is a partial backup (as opposed to a full backup),
          bakonf will make the following tests:

         1. size of file saved in database ≠ actual file size? if
            true, the file will be backed up;
         2. md5 hash saved ≠ actual md5 hash? if true, file will
            be backed up;
         3. sha hash saved ≠ actual sha hash? if true file will be
            backed up;
         4. file will not be backed up.

          Here we could introduce another form of backup, only
          file metadata backup, in case file contents hasn't
          changed, but file mode (permissions, owner) have.

   symbolic links
          bakonf doesn't follow symbolic links; it treats a
          symbolic link like a configuration file (its
          configuration data resides in its name and its target).
          The tests made by bakonf are, in order:

         1. link target must be equal, or the file is backed up
         2. user and group ownership must be equal, or the file is
            backed up
         3. permission bits must be equal, or the file is backed
            up
         4. the file is not backed up

   block devices, character devices, fifos, sockets
          bakonf always selects these to backed up. Of course,
          some of them won't be backed up by tar, but regarding
          bakonf, it will select those for backup.

   when the file type in archive is different than actual file
          type
          in this case, bakonf always selects the file for
          archiving
     __________________________________________________________

4.2. Metadata

   Metadata allows you to have more information about a system
   than is available in the filesystem. The current implementation
   allows you to store output of shell commands. Suggestions about
   other items are welcome.
     __________________________________________________________

4.2.1. Partition table

   The most important metadata item is partition table about your
   disks, in the eventuality that you have a data error in
   partition table. The command to back this up varies, for
   example:

   OS: GNU/Linux

   Command: sfdisk -d /dev/hda

   OS: FreeBSD

   Command: fdisk /dev/ad0
     __________________________________________________________

4.2.2. Device list

   Having the device list is and their hardware configuration is
   useful in order to have a quick overview if you want to clone
   the configuration from one system to another (to see
   correspondence between config files and hardware config).
   Examples of scanning the configuration:

   OS: GNU/Linux

   Command(s): lspci -vv; lsusb -vv

   OS: FreeBSD

   Command(s): pciconf -lv; usbdevs -v
     __________________________________________________________

4.3. What can I use bakonf for?

   At least for:

     * Configuration rollback. Since the archives are small, you
       can keep many versions, but unlike in differential backup,
       here one archive contains all the needed data.
     * Configuration cloning. You can take a bakonf-generated
       archive from one system to another and 'clone' as much of
       the settings as you want.
     * Quick restore of a server in case of catastrophic harddisk
       failure. Just reinstall the OS and put the config files
       back.
     __________________________________________________________

4.4. Requirements

   To use bakonf, you must have the following:

     * a Unix-like operating system (with compatible filesystem
       layout)
     * python version 2.4 or higher
     * xml parsing support for python, in order to use python's
       xml.dom.minidom; feel free to hack bakonf to change the
       configuration system if you want so
     __________________________________________________________

5. Configuration

   Note Note


        Older bakonf versions (< 0.5) had an entirely different config
        file. If you upgraded, be sure to forward you changes to the
        new config files.

   bakonf uses a main configuration file /etc/bakonf/bakonf.xml,
   which does some standard settings and tells bakonf what other
   files to include. These additional files are usually located in
   /etc/bakonf/sources and tell bakonf how to handle some special
   cases.
     __________________________________________________________

5.1. Configuration language

   The configuration file is written in XML, must be encoded in
   utf-8 and must have the document tag bakonf.

   The file can contain the following tags:

   <include path="CONFIGFILE_PATTERN"/>
          tells bakonf to also parse any files which match the
          given shell pattern. These are files which modify
          bakonf's own behaviour, and are usually located in
          /etc/bakonf/sources. These are not directories to be
          backed up! (Although, if modified and included by the
          filesystem element, they will be).

   <filesystem>
          Starts declarations about files to be backed up, and can
          contain:

        <scan path="SHELL-PATTERN"/>
                tells bakonf to add any file or directory which
                matched shell pattern PATTERN to its include list.
                These can be files or directories. Bakonf will
                descend directories, but will not follow symbolic
                links! The symlinks are considered configuration
                items also, so they will be backed up themselves.

        <noscan regex="REGEXP"/>
                tells bakonf to ignore any file or directory which
                matches the regular expression REGEXP from the
                archive; it won't even open or analyse those
                files.

   <metadata>
          Starts declarations about metainformations to be
          included in the archive, and can contain:

        <storeoutput command="SHELL-COMMAND" destination="PATH IN
                ARCHIVE"/>
                Tells bakonf to execute the given SHELL-COMMAND
                and include its output in a file named
                metadata/PATH IN ARCHIVE in the created archive.
                For example, the element:

<storeoutput command="cat
                    /proc/version"
                    destination="proc/version"/>

                will create a file in the archive with the name
                metadata/proc/version which will contain the
                /proc/version file.

   <config>
          Configuration section that modifies the behaviour of
          bakonf. It can contain:

        <virtualsdb path="DBNAME">
                This elements contains in its path attribute the
                filename of the virtuals database.

   The order of precedence for scan/noscan is:

     * bakonf will start scanning all items defined with scan
     * if at any point in the filesystem scan, the current
       file/directory matches any one of noscan REGEXPs, the scan
       will ignore it. For directories, that means ignoring all
       the files they contain, so please be careful about it.

   Using these, you can select where you want bakonf to look for
   files for archiving. The default config file includes /etc,
   /usr/etc, /usr/local/etc and some others (look in /etc/bakonf
   after installing).

   Example main configuration file (the file included in the
   distribution):
<bakonf>
<!--
     Bakonf main configuration file. Tune to your system.
     See also the files in the sources subdirectory (included by defaul
t)
-->
<filesystem>
    <!-- Standard directories -->
    <scan path="/etc" />
    <scan path="/usr/etc" />
    <scan path="/usr/local/etc" />
    <scan path="/var/lib/alternatives" />
</filesystem>
<!-- Include by default the other configuration files -->
<include path="/etc/bakonf/sources/*.xml" />
</bakonf>

   Example GNU/Linux proc configuration file (included in the
   distribution):
<bakonf>
<!--
     File which contains hardware related informations, mostly
     extracted from the /proc filesystem (under GNU/Linux)
-->
<metadata>
<!-- Proc values -->
<storeoutput command="cat /proc/version" destination="proc/version"/>
<storeoutput command="cat /proc/dma" destination="proc/dma"/>
<storeoutput command="cat /proc/interrupts" destination="proc/interrupt
s"/>
<storeoutput command="cat /proc/ioports" destination="proc/ioports"/>
<storeoutput command="cat /proc/iomem" destination="proc/iomem"/>
<storeoutput command="cat /proc/cpuinfo" destination="proc/cpuinfo"/>
<storeoutput command="cat /proc/partitions" destination="proc/partition
s"/>
<!-- Also hardware information -->
<storeoutput command="/sbin/lspci -vv" destination="lspci.txt"/>
<storeoutput command="/sbin/lsusb -vv" destination="lsusb.txt"/>
</metadata>
</bakonf>
     __________________________________________________________

5.2. File list

   bakonf is composed of:

   /etc/bakonf/bakonf.xml
          Main configuration file.

   /etc/bakonf/sources/*.xml
          Configuration files for special cases (config files
          outside of etc dirs).

   /usr/sbin/bakonf.py
          Main program

   /etc/cron.d/bakonf
          Cron file, by default it does not run bakonf, you must
          uncomment a line to run it.

   /var/lib/bakonf/archives
          Default directory for configuration file archives.

   Caution

           You must decide yourself what to do with the configuration
           archives after bakonf creates them!
     __________________________________________________________

6. Using bakonf

6.1. Backup phase

   For details about the actual parameters to bakonf, see its
   manpage.

   To use bakonf, choose to either:

     * run it manually, when you want, either always with -L0 or
       with a combination: weekly with -L0, daily with -L1
     * use the provided cron script to run it automatically, or
       create your own

   In any case, you have to do something with the generated
   archives. Write the to floppy, tape, CD, other machine, but
   don't just ignore them, you defeat the purpose of bakonf.
     __________________________________________________________

6.2. Restore phase

6.2.1. Configuration rollback

   In this case, just make sure you have the bakonf-generated
   archive near the date in the past you are interested in. If so:

    1. if your system uses packages/ports, compare the actual
       package list with the one recorded by bakonf when it
       created the archive
    2. install/remove software as needed
    3. copy the configuration files for the services you want to
       rollback over the current files
     __________________________________________________________

6.2.2. Complete system restoration

   If you had a catastrophic Al failure, you should follow these
   steps:

    1. Reinstall the operating system on a clean machine. Use the
       given information in the /metadata directory in the archive
       to achieve an as close as possible configuration as the old
       system (e.g. partition layout, packages installed, etc.)
    2. Copy all the files in the archive in the filesystem,
       overwriting the defaults from the packages.
