That "answer" is dishonest. I only needed the first point to reach that
conclusion. It is supposed to be about "su command replacement", what leads
to believe that 'su' should not be used on systems with systemd. According
to the author: "[Lennart Poettering] explains that 'you can use su and sudo
as before, but don't expect that it will work in full'", what leads to
believe that systemd has forced 'su' to lose features. One click on the
provided link and you discover that the author removed the last four words in
Lennart Poettering's sentence, which is, in full:
Well, you can use su and sudo as before, but don't expect that it will work
in full, because it never did.
https://github.com/systemd/systemd/issues/825#issuecomment-127957710
Lennart Poettering explains:
['su' is] supposed to open a new session and change a number of execution
context parameters (uid, gid, env, ...), and on the other it's supposed to
inherit a lot concepts from the originating session (tty, cgroup, audit,
...). Since this is so weakly defined it's a really weird mix&match of old
and new paramters.
https://github.com/systemd/systemd/issues/825#issuecomment-127917622
That part is, again, stripped out from a quote in Stack Exchange's answer.
The quote only keeps the statement that follows: "su is really a broken
concept", as if that blunt affirmation was not justified. How honest is
that?
Notice that 'man su' does not say otherwise:
The current environment is passed to the new shell. The value of $PATH is
reset to /bin:/usr/bin for normal users, or /sbin:/bin:/usr/sbin:/usr/bin for
the superuser.
'machinectl shell' does *not* "replace" 'su'. 'su' works exactly the same
whatever the init system, including systemd. 'machinectl shell' is a new
feature. Nobody is forced to use it. Unlike 'su', it provides a shell that
inherits nothing from the originated session, i.e., the same shell the user
would get logging in "normally".
https://wiki.debian.org/Debate/initsystem/ is good material to compare init
systems: defenders of every popular init system argue in their respective
favors and criticizes the other init systems. The arguments are mainly
technical, harder to understand than lies such as "systemd replaces good ol'
'su'".
