Updated/Revised February 2020
Tested on FreeBSD 9.0 through FreeBSD 12.1, with Retrospect 7.7 through Retrospect 16.6.
New for 2019!
For FreeBSD 11.2+ and FreeBSD 12.0+, you will need to use Retrospect Server version 16.5 or newer (older versions do not work).
The kernel in these newer versions of FreeBSD passes a Linux ABI llistxattr response that earlier versions of the Retrospect Server cannot handle (this also causes problems with other backup programs, see here).
Using a version of Retrospect Server older than 16.5.0 on FreeBSD 11.2/12.0 will result in this error when it tries to back up files:
can't read, error -1114 (unexpected end of file)
Another issue: Retrospect cannot seem to create a password (stored in /var/log/retroclient.state) with the CentOS libraries on FreeBSD.
During initial installation or when attempting to set a password ("retroclient -setpass"), it would result in this being repeated over and over:
That password is invalid, password length must be at least 4 That password is invalid, password length must be at least 4 ...
Or you simply get this message when trying "setpass" and then nothing happens:
Overriding existing password.
This worked for us in the past with the 32-bit Fedora Linux libraries (no longer part of FreeBSD).
There is an easy work-around:
Just create a blank retroclient.state file ("touch /var/log/retroclient.state") and set the password on first connection with the Retrospect Server when adding the client.