The problem: Some time ago, I had a server “in the wild” from which I
wanted some data backed up to my rsync.net account. I didn’t want to
put sensitive credentials on this server in case it got compromised.
The awesome admins at rsync.net pointed out their subuid feature. For
no extra charge, they’ll give you another uid, which can have its own
ssh keys, whose home directory is symbolically linked under your main
uid’s home directory. So the server can rsync backups to the subuid,
and if it is compromised, attackers cannot get at any info which didn’t
originate from that server anyway.