RDUP-BACKUPS(7) rdup RDUP-BACKUPS(7)NAMErdup-backups - introduction into making backups with rdup
INTRODUCTION
rdup is a simple program that prints out a list of files and directo‐
ries that are changed changed on a filesystem. It is more sophisticated
than for instance find, because rdup will find files that are removed
or directories that are renamed.
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 per‐
form a backup.
Currently rdup consists out of three basic utilities:
rdup With rdup you create the file list on which later programs in
the pipeline can work. The default output format also includes
the files' content. rdup can be seen as a tar replacement in
this respect, but rdup also allows for all kinds of transforma‐
tions of the content (encryption, compression, reversal), see
the -P switch in rdup(1) for more information.
rdup-tr
With rdup-tr you can transform the files rdup delivers to you.
You can create tar, cpio or pax files. You can encrypt path‐
names. rdup-tr is filter that reads from standard input and
writes to standard output. See rdup-tr(1) for more information.
With rdup and rdup-tr you can create an encrypted archive which
is put in a directory structure that is also encrypted.
rdup-up
With rdup-up you can update an existing directory structure with
the updates as described by rdup.
rdup-up reads rdup input and will create the files, symbolic
links, hard links and directories (and sockets, pipes and
devices) in the file system. See rdup-up(1) for more informa‐
tion.
So the general backup pipeline for rdup will look something like this:
create filelist | transform | update filesystem
( rdup | rdup-tr | rdup-up )
Note 1:
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.
Note 2:
The use of rdup-tr is optional.
BACKUPS AND RESTORES
For rdup there is no difference between backups and restores. If you
think about this for a minute you understand why.
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 during the backup you just need to reverse those operations
during the restore.
BACKUPS
It is always best to backup to another medium, be it a different local
harddisk or a NFS/CIFS mounted filesystem. You can also use ssh to
store file on a remote server, ala rsync (although not as network effi‐
cient).
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
We need a little help here in the form of the rdup-simple script. Keep
in mind that the following scripts can also be run remotely with the
help of ssh.
The following script implements the algorithm of rdup-simple.
#!/bin/bash
# some tmp files are saved in ~/.rdup. This directory must exist
DIR=/home # what to backup
BACKUP=/vol/backup
TODAY=$(date +%Y%m/%d)
LIST=~/.rdup/list-$HOSTNAME
STAMP=~/.rdup/timestamp-$HOSTNAME
# for remote backup, this has to run on the remote host!
BUGBUG
RET=$?
case $RET in
2|*)
echo Error >&2
exit 1
;;
1)
# full dump, remove file-list and time-stamp file
rm $LIST $STAMP
;;
0)
# inc dump
# do nothing here
;;
esac
# this is the place where you want to modify the command line
# right now, nothing is translated we just use 'cat'
rdup -N $STAMP -Pcat $LIST $DIR | rdup-up $BACKUP/$HOSTNAME/$TODAY
# or do a remote backup
#rdup -N $STAMP -Pcat $LIST $DIR | ssh root@remotehost \
# rdup-up $BACKUP/$HOSTNAME/$TODAY
LOCAL BACKUPS
With rdup-simple you can easily create backups. Backing up my home
directory to a backup directory:
rdup-simple ~ /vol/backup/$HOSTNAME
This will create a backup in /vol/backup/$HOSTNAME/200705/15. So each
day will have its own directory. Multiple sources are allowed, so:
rdup-simple ~ /etc/ /var/lib /vol/backup/$HOSTNAME
Will backup your home directory, /etc and /var/lib to the backup loca‐
tion. Also if you need to compress your backup, simple add a '-z'
switch:
rdup-simple -z ~ /etc/ /var/lib /vol/backup/$HOSTNAME
REMOTE BACKUPS
For a remote backup to work, both the sending machine and the receiving
machine must have rdup installed. The currently implemented protocol is
ssh.
Dumping my homedir to the remote server:
rdup-simple ~ ssh://miekg@remote/vol/backup/$HOSTNAME
The syntax is almost identical, only the destination starts with the
magic string 'ssh://'. Compression and encryption are just as easily
enabled as with a local backup, just add '-z' and/or a '-k keyfile'
argument:
rdup-simple -z-k 'secret-file' ~
ssh://miekg@remote/vol/backup/$HOSTNAME
Remember though, that because of these advanced features (compression,
encryption, etc, ...) the network transfer can never be as efficient as
rsync.
ALSO SEErdup(1), rdup-tr(1), rdup-up(1) and http://www.miek.nl/projects/rdup/
1.1.x 15 Dec 2008 RDUP-BACKUPS(7)
