On Sun, Dec 27, 2020 at 11:56:21PM +0000, Graham Seaman wrote: > I'm having problems with pppd and an intermittent phone line
Wow. Memories fading :-)
OK, my recollection on inittab is a bit dusty, and I have little
experience with systemd (trying to keep it that way). But I'll
try a shot at it.
The idea of inittab was to keep an eye on some processes: when
they died, they were restarted ("respawn", in inittab parlance).
This was init's job (thus inittab). Its main customers were
the login processes. At their other end were serial lines
attached to terminals (ah, vt220...). A user logged in at
one of those things, the login handed off to a shell or something,
when the user logged off the shell terminated, the calling
login terminated and... respawn.
Other things followed, typically daemons and... pppd.
Then came SysV: daemons had to take care of themselves, PID
files grew like mushrooms all over the place. It was bad
times. The inittab was still there, mind you, but it was only
tending to the Linux consoles (tradition perhaps :-) and to
non-existing serial terminals. My system still has one,
perhaps yours too.
Now with systemd, we've turned full circle (unfortunately, with
seventeen layers of complexity stacked in-between). In theory,
systemd /should/ be able to do exactly what init used to do
back then.
Searching for "inittab systemd" via our favourite search engine
(no, not that one with the big G) yields a couple of good
hits. In [1] there's an example on how to translate an inittab
entry into a systemd unit file.. In [2] you can see where the
systemd unit files for your serial console live under Debian,
perhaps there /is/ already something near that for pppd?
Assuming you are on Buster... the list of files for package
ppp (where pppd lives) is here [3]. No, no unit for respawn,
alas. Only one to kick systemd's DNS service on connect and
disconnect events (/lib/systemd/system/pppd-dns.service).
Seems like you'll have to fashion one after some /lib/systemd/...tty.service.
Perhaps there's someone around here who has done that to
help you out. Tip: don't put it in /lib/systemd/... This
place os for your distro. Put it somewhere in /etc/systemd/...
that's for you, the admin. I can't provide details -- no
experience with that.
I'd try to file a bug against ppp: they should be providing
a systemd unit file.
Cheers
- t
[1]
https://forums.opensuse.org/showthread.php/475468-In-search-for-a-inittab-entry-replacement-for-systemd#7
[2] https://wiki.debian.org/systemd#line-288
[3] https://packages.debian.org/buster/amd64/ppp/filelist
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