RDUP-BACKUPS

NAME

INTRODUCTION

A long time ago rdup included a bunch of shell and Perl scripts that implemented a backup policy. These could be used in a pipeline to perform a backup.

Currently rdup consists out of three basic utilities:

rdup

With rdup you create the filelist on which later programs in the pipeline can work. With rdup -c the file's contents is also echo-ed to stdout. See rdup(1) for more infomation.

rdup-tr

With rdup-tr you can transform (encrypt, compress, whatever...) the files rdup delivers to you.

rdup-tr reads rdup input and will create rdup -c output. See rdup-tr(1) for more information.

rdup-up

With rdup-up you can update an existing directory structure with the updates as described by rdup.

rdup-up reads rdup -c input and will create the files, symlinks, hardlinks and directories (and sockets, pipes and devices) in the file system. See rdup-up(1) for more information.

So the general backup pipeline for rdup will look something like this:

    create filelist  |  transform file content  |  update filesystem
    ( rdup           |  rdup-tr                 |  rdup-up )

Note that the same sequence is used for restoring. In both cases you want to move files from location A to B. The only difference is that the transformation is reversed when you restore.

There is a little shell script that can be used to create a hard linked directory structure, this script rdup-ln.sh is installed in '/usr/lib/rdup/'. The script looks back for previous backup and then creates a hardlinked directory structure. By using this script you create a YYYYMM/DD backup structure, where each YYYYMM/DD directory contains a full view of your filesystem at that date. This script very much depends on being able to use GNU date and GNU cp.

From the return code of this script you know what to do, if the exit code is 0 an incremental backup needs to be made. If the exit code is 1 a full backup is in order. An exit code of 2 means there was some kind of error.

With these three (four) tools you can create your own backup solution, see SNAPSHOT BACKUPS later in this document.

TYPES OF OUTPUT

1.

a list of pathnames and path attributes

2.

a list of pathnames and path attributes and the files' contents

The latter is often called 'rdup -c' output after the switch (-c) which enables this ouput. 'rdup -c' output is comparable to archive formats like tar or pax.

The first one is just called the normal or list output.

In rdup(1), rdup-tr(1) and rdup-up(1) it says what output a command can create and what input it expects.

BACKUPS AND RESTORES

Making a backup means copying a list of files somewhere else. Restoring files is copying a list of files back to the place they came from. Same difference. So rdup can be used for both, if you did any transformation with rdup-tr during the backup you just need to reverse those operations during the restore.

BACKUPS

If you backup to a local disk you can just as well use rsync or plain old tar, but if you store your files at somebody else's disk you will need encryption. This is where you go beyond rsync and rdup comes in. Rsync cannot do per-file encryption, sure you can encrypt the network traffic with ssh, but at the remote side your files are kept in plain view.         
If you implement remote backups, the easy route is to allow root access on the backup medium. If the backup runs without root access the created files will not have their original ownership. For NFS this can be achieved by using no_root_squash, for ssh you could enable PermitRootLogin. Note that this may be a security risk.

SNAPSHOT BACKUPS

The following script implements the algorithm of rdup-simple.

#!/bin/bash

# some tmp. file are saved in ~/.rdup. This directory must exist

DIR=/home           # what to backup
BACKUP=/vol/backup
TODAY=$(date +%Y%m/%d)  # same as in rdup-ln.sh
LIST=~/.rdup/list-$HOSTNAME
STAMP=~/.rdup/timestamp-$HOSTNAME

# for remote backup, this has to run on the remote host!
/usr/lib/rdup/rdup-ln.sh $BACKUP/$HOSTNAME
RET=$?

case $RET in
    2|*)
        echo Error >&2
        exit 1
        ;;
    1)
        # full dump, remove filelist and timestamp file
        rm $LIST $STAMP
        ;;
    0)
        # inc dump
        # do nothing here
        ;;
esac

# this is the place where you want to modify the commandline
#
# right now, nothing is translated we just use 'cat'

rdup -N $STAMP $LIST $DIR | rdup-tr -Pcat | rdup-up $BACKUP/$HOSTNAME/$TODAY

# Note that rdup-up expects rdup-c output, so if you leave out
# rdup-tr, you must tell rdup to generate the correct output
# rdup -c -N $STAMP $LIST $DIR | rdup-up $BACKUP/$HOSTNAME/$TODAY

# or do a remote backup
#rdup -N $STAMP $LIST $DIR | rdup-tr -Pcat | ssh root@remotehost \
#       rdup-up $BACKUP/$HOSTNAME/$TODAY

RESTORES

ALSO SEE

Index

NAME

INTRODUCTION

TYPES OF OUTPUT

BACKUPS AND RESTORES

BACKUPS

SNAPSHOT BACKUPS

RESTORES

ALSO SEE