backupd - a backup solution for heterogenous networks

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  1. What is it?
  2. Why backupd?
  3. What does it do?
  4. What does it not do?
  5. An example please...
  6. How do I access my data in case of an emergency?
  7. What copyright does it have?
  8. Where do I get the stuff?
  9. What is planned for the future?

What is it?

backupd is a small client/server backup solution for environments with different operating systems. It follows strictly the KISS principle, is easy to set up and to administer.

Why backupd?

My working environment here at home is a small network with most boxes running Linux, but some others running Windows NT or OS/2. I'm doing network administration for other people where the situation is similar or even more biased towards Windows.

I have had a SCSI tape drive and several disks for backup purposes in the local net. However, doing backups was a pain, since I had no backup software that was available for every operating system, and so I had to manually connect the DAT drive to one of the computers, reboot computers, work with different software and more.

Linux itself is not very much a problem in this respect, since gtar supports backups via the network. Unfortunately, it uses rsh for this purpose, with all security related consequences. For OS/2, rsh can also be used, but what if you don't want any user to have logins on the server used for a backup?

So I wrote backupd as a more or less generic solution for my backup problem. It may solve yours, too.

backupd ...

What does it do?

backupd is a client/server application. The server is Linux only (well, there's nothing special about the code, it should compile under other Unices without changes, but who cares?). The clients run under NT or Win95 (there's one problem with Win95, see below), OS/2 and Linux. The server supports a nearly unlimited count of resources. When connected, a client tells the server, which resource it wants to write or read.

The name of the package is somewhat misleading, since client and server do not really care about backups. What they do is transmitting data to and from a resource. This makes backupd very simple, since the client does not care how to collect files on the local disk. It relies completely on another program to do that. On the server side, it's the same: The server does not know anything about tapes or disks, it pipes the data into a shell command.

In addition, the server does not really run as a daemon but is started by inetd. This way, it does not use any resources when it is not used.

What does it not do?

The client is not able to read files, scan disks or any other thing, you expect from a generic backup program. There are lots of programs available that do archiving, including gtar, so there's no need to write another such program. This does also mean, that the client does not provide a capability to browse an archive (it does not know anything about archives).

The server does not know anything about tapes, disks or other stuff, it pipes the data received from the client into a shell command. The server relies on the tcpwrappers module and inetd for security (or your firewall, if you have one). If your client is able to connect to the server, the server will take happily all data it gets from the client and write it to a resource, if requested to do so.

Another thing, the server is not able to do is to start the backup operation itself (it is almost impossible to do that in a portable way, and most Windows and OS/2 clients do not run 24/7 anyway). You have to start the backup from the client(s).

Both programs also don't do encryption. If you need encryption, you may tunnel the connection over ssh (I've not tried this, however).

By concentrating on just one thing (getting data from and to a server), both programs are very small and simple.

So backupd is clearly not a solution for pure Unix networks (but it may have some advantages to use it even in such an environment). It is aimed for small heterogenous LANs (but then, there's nothing that keeps you from making backups via a dialup connection, all you need is TCP/IP networking).

An example please...

Server resources are defined in /etc/backupd.conf. Here is a sample for a resource named "tape0":

user  	 = "nobody"
group 	 = "disk"
write  	 = "dd of=/dev/st0 bs=32k"
read  	 = "dd if=/dev/st0 bs=32k"
lockfile = "/tmp/tape0.lock"

The section is more or less self explaining. It describes, what the server has to do, if the client requests reads from or writes to the given resource.

Now, as you have prepared your server using the config file shown above all you have to do is to insert a tape into your tape drive and issue the following command on your OS/2 or NT box:

tar -cf - . | backupc -h backuphost -w tape0

The backup client will then connect to the host named "backuphost", and write all data it gets on stdin to the resource tape0.

For read access, use

backupc -h backuphost -r tape0 | tar -xf -

So, the main part is to setup the server, but this has to be done only once. On the client, you need some sort of archiver. Fortunately, gtar is readily available for both, OS/2 and Win32 and works great with backupc.

As you can easily see, the solution is very flexible. You may pipe the data through gzip on the client or on the server side, or even zip it on the client and unzip it on the server side, or use any other shell command to filter the data. However, you are not restricted to filters. You might use something like

write = "cat > /backups/thisclient/`date +%Y-%m-%d.tar`"

to create daily backups from a client, or even use a much more complex shell script that does numbered backups or whatever.

How do I access my data in case of an emergency?

backupd does not help you with that. So, if the hard disk on your NT box gets damaged, and you are no longer able to boot your operating system, you have a problem. Here are some proposed solutions:

backupd simplifies the task of making backups so that you are able to do it more regularily. It does not include any help for restoring systems from scratch.

What copyright does it have?

Here's the copyright for the sources and the binaries (the copyrights for the binary GNU tools distributions for OS/2 and NT are different, see separate texts in the archives):

This software is provided 'as-is', without any express or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software.

Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions:

  1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
  2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
  3. This notice may not be removed or altered from any source distribution.

Where do I get the stuff?

I will probably prepare a RPM archive in the near future. Since this is some work (it's not just installing files, /etc/inetd.conf and /etc/services have to be changed), you have to install the software yourself for now (read the file INSTALL.TXT in the source archive!).

I'm not providing a binary archive, since backupd is a really simple program and it's naked C (no C++) this time, so compiling should be straight forward.

In addition to the source archive (which will produce the backup client and server executables for Linux), there are two archives that contain client executables for Windows (NT and 95) and OS/2. These archives do also contain a tar port for the operating system, so, with the exception of Windows 95, you do not need any other software to do backups.

Regarding Win95: There's a problem with Windows 95 that needs another program to work around it: the MS-DOS prompt under Win95 is not able to do real pipes (it uses intermediate files like in plain old DOS), so you have to use a replacement for COMMAND.COM. I recommend the tcsh port from

The README says it's an NT port, but it works great under Win95 as far as I can tell. Get it and use

tcsh -c "backupc -h backupdhost -r tape0 | tar -xvpf -"

instead of the syntax described elsewhere in this document. Note: You do not need tcsh when using Windows NT.

I'll try to provide more perfect client binary archives (containing all you need, not less and not more) in the future.

The following packages are available from (replace the xx.y by the current version number):

backupd-0.xx.y-src.tar.gz Source archive Client binary + gtar for OS/2 Client binary + gtar for NT/Win95
pkg/ More Unix like utils for Win32
pkg/ gtar for OS/2 with source (this port was done by Andreas Kaiser)

What is planned for the future?

The next version will have user based access control (this is already done for PAM based Linux systems like RedHat) and data stream encryption (using the blowfish encryption algorithm).


Letzte Ă„nderung: 26-Mar-2008
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