This commit adds support to /etc/hostname for substitution of $ from
wordlists located in /etc,/run,/usr/lib}/systemd/. Each $ is resolved to
a number (1,2,3...) and the corresponding file "1" is opened to acquire
the word. With that we can do a petname [1] style hostname in systemd,
e.g. below a possible expansion for a hostname template:
$-$-$-???? -> wildly-happy-octopus-92a9
The substitution of words is stable (based on machine-id) but if the
wordlist changes the hostname would change. We could pick it once and
cache it but Lennart did not like this so this version instead always
picks it (based on offset of the file so the operation is cheap). To
persist it one can use the `firstboot.hostname` credential. One a live
system this will be expanded and then written in the expanded form to
/etc/hostname.
This also includes a wordlist from the "petname" project that can be
optionally installed.
Thanks to Dustin Kirkland for this wonderful project.
[1] https://github.com/dustinkirkland/petname
---
I'm a bit unsure if this should include the word lists (I think its nice
to have them though) and if so if they should be their own commit.
Lennart Poettering
864f559b37