Mondo rescue is not present in the official debian lenny repositories.

If  you want install mondo using apt-get you’ll have to add the following to your /etc/apt/sources.list file:

deb ftp://ftp.mondorescue.org/debian 5.0 contrib
deb-src ftp://ftp.mondorescue.org/debian 5.0 contrib


Then run apt-get update and apt-get install mondo.
That's it.

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