Backup application recommendations

[Sad Clouds <cryintothebluesky%gmail.com@localhost>]

Hello, could anyone recommend a backup application for a few desktop PCs
at home running Linux and NetBSD. Something simple and easy to use:

- NetBSD or FreeBSD will be a central backup server.

- Need fully automated, setup-and-forget application, which can do full
and incremental backups to a remote server, with various retention
policies, etc.

- Need to be able to cope with unexpected reboots (i.e. user shutting
down a PC) and later continue backup where it was interrupted, instead
of starting from the beginning.

- Would be nice to have periodic checksumming of backup data, in case
of bit rot. Alternatively I could use FreeBSD + ZFS.

- Would be nice to have GUI and encryption, but not critical.

- Would be nice to have easy, point-and-click restore functionality,
but not critical.

- Doesn't need to be free, i.e. I'm willing to pay for software, as
long as it is not too expensive for what it is.

Thanks.