Hello Jean-Louis!
Do you have the '/usr/local/lib/perl5/site_perl/5.12.2/Amanda/XferServer.pm' file?
Yes.
How do you configured amanda?
I installed Amanda from FreeBSD port, the configure line for amanda-server looks like this:
$ ./configure --libexecdir=/usr/local/libexec/amanda --without-amlibexecdir --with-amandahosts --with-fqdn --with-dump-honor-nodump --prefix=/usr/local --disable-glibtest --with-user=backup --with-group=operator --with-bsdtcp-security --with-bsdudp-security --with-ssh-security --with-gnutar-listdir=/var/amanda/gnutar-lists --with-gnutar=/usr/local/bin/gtar --without-client --without-gnuplot --disable-s3-device --prefix=/usr/local --mandir=/usr/local/man --infodir=/usr/local/info/ --build=amd64-portbld-freebsd8.1
-- Toomas Aas
