Exploring the Relax and Recoverbackup and rescue system



Because ReaR is optimized for cronjobs, it does not produce a lot of output in normal cases. rear -v activates the verbose mode. Simulation mode (rear -s) shows the scripts included with the configuration. Customizations are easy to add. A user only has to create a shell script and drop it into the desired path (Figure 3). Additional options are listed on the ReaR homepage.

Figure 3: ReaR Simulation Mode.

Extended Possibilities

ReaR can do much more than just the standard functions. For instance, the administrator can send the result files via email, thus invoking a one-way, highly secure communication channel to get the recovery image from a system that is down to one that is protected.

The recovery image comes with passwords, private keys, and so on – with few surprises. A possible exception is authentication for commercial backup clients, which you can disable from IBM Tivoli Storage Manager. The recovery image does not need to be specially protected, but adding authentication does increase integrity.

ReaR is very easy to extend thanks to its modular design. And, ReaR copes well with (U) EFI, in addition to supporting Itanium and PowerPC systems.

Bottom Line

Although ReaR was developed in 2006, this extraordinary recovery tool is still unknown to many administrators. The fact that ReaR is implemented using Bash scripts might make it seem unpolished, and yet, ReaR is actually highly professional. The small size of the Bash scripts, which are usually not longer than one screen page, also makes for easy handling. Most of the configuration takes place in the few configuration files (see Table 2).

Table 2


File Function
/usr/sbin/rear ReaR tool
/etc/rear/local.conf System-specific configuration files
/etc/rear/site.conf Site-specific configuration files. Not applied as a default. Can be provided through other deployment tools or RPM-/Debian packages.
/var/log/rear/ Log files
/tmp/rear Temporary working directory. Must be manually deleted after an error.
/usr/share/rear All script components
/usr/share/rear/conf/default.conf Annotated default configurations with all available parameters that the admin can copy as required to local.conf or site.conf

Thanks to well-chosen defaults, the configuration is very simple and rewarding, with a very high degree of automation for smaller projects or individual servers. In fact, ReaR supports complex scenarios and the inclusion of highly customized details.

ReaR's modular design makes it easily expandable and easy to use. SEP has even chosen ReaR as a substitute for its own disaster recovery tool and provides the necessary SESAM support. Details regarding official documentation are available at SEP SESAM [6].

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