Decide what to do with machine-id

Originally created by @intrigeri on #7100 (Redmine)

Modern GNU/Linux tools (D-Bus, systemd) relies more and more on /etc/machine-id and/or /var/lib/dbus/machine-id (depending on the OS, versions, etc.). In most situations we care about, if not all, this ID should not be leaked to the network. If it is, then:

• if we set the same machine-id everywhere, then users are all in the same anonymity set; but this also leaks that they’re using Tails
• if we set unique machine-id on boot, then we don’t leak that users are using Tails, and applications that rely on machine-id working on the LAN work; OTOH, if machine-id leaks on the Internet, then the fact that users are not in the same anonymity set can be a problem

We should first evaluate if/how machine-id can be leaked, and then think about this all, and decide something.

team: bertagaz

Related issues

• Related to #5821 (closed)
• Related to #5630 (closed)