rdup-backups - introduction into making backups with rdup
is a simple program that prints out a list of files and directories
that are changed changed on a filesystem. It is more sophisticated than for
, 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 perform a
consists out of three basic utilities:
- 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 transformations of the content
(encryption, compression, reversal), see the -P switch in rdup(1) for more
- With rdup-tr you can transform the files rdup delivers to you. You
can create tar, cpio or pax files. You can encrypt pathnames.
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.
- 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 information.
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.
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
can be used for both, if you did any transformation with
during the backup you just need to reverse those operations during
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
store file on a remote server, ala rsync (although not as network efficient).
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
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
, for ssh
you could enable PermitRootLogin
Note that this may be a security risk.
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
The following script implements the algorithm of rdup-simple
# some tmp files are saved in ~/.rdup. This directory must exist
DIR=/home # what to backup
# for remote backup, this has to run on the remote host!
case $RET in
echo Error >&2
# full dump, remove file-list and time-stamp file
rm $LIST $STAMP
# inc dump
# do nothing here
# 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/$TODAY
you can easily create backups. Backing up my home
directory to a backup directory:
rdup-simple ~ /vol/backup/$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 location. Also
if you need to compress your backup, simple add a '-z' switch:
rdup-simple -z ~ /etc/ /var/lib
For a remote backup to work, both the sending machine and the receiving machine
must have rdup
installed. The currently implemented protocol is
Dumping my homedir to the remote server:
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' ~
Remember though, that because of these advanced features (compression,
encryption, etc, ...) the network transfer can never be as efficient as
rdup(1), rdup-tr(1), rdup-up(1) and http://www.miek.nl/projects/rdup/