[1] https://www.freedesktop.org/software/systemd/man/systemd.tim...
simpler to the point that you need whole libraries and helpers (such as https://www.freeformatter.com/cron-expression-generator-quar...) to convert from readable time to cron specifications ?
Meanwhile, sd is just
[Timer]
OnCalendar=weeklyBut you loose the main point, that is consistency of syntax. Nowadays thanks to systemd I can use the exact same syntax to configure my daemons, my network, my DNS resolver, my timers, my locale, etc etc. The mental burden is way lighter than with the traditional UNIX toolset.
You could have made the same consistency and mental burden argument about the crontab syntax. There are a lot of things in Unix which are table-driven and the tables take the form of one line per record with fields delimited by whitespace, blank lines ignored, and line comments introduced by hash.
Indeed these are your job scheduler (crontab), your mount points (fstab), your local host name resolution (hosts), your NS switch (nsswitch.conf), your terminal login services (ttys), your device permissions (fbtab), your automounts (auto_master), your plug-and-play device permissions (devfs.conf), your network services (inetd.conf), your MAC policy (mac.conf), your local network name resolution (networks), your call-out telephone numbers (phones), your network protocol name map (protocols), your RPC service map (rpc), and your network port name map (services).
And those are just the ones in /etc .
This set of table files with a common syntax is just as consistent and as light a burden as the set of .INI files that you are talking about. And any argument that you can make about things like having to remember what the fields mean can also be made just as much about the .INI files.
You only "need" to read the man page - the same as with systemd (asuming it still uses man, and not its own custom help viewer). If you'd read said man page, you'd know you can just type @weekly, for such a simple time period.
It never became it, either. It was fairly quickly forked. Several times. Debian cron was forked from PD cron in 1994 by Ian Jackson, for example. The "standard one that everyone used to use" but only in the limited field of Debian Linux (and no longer, nowadays with Debian Linux version 9) was that fork, which M. Jackson actually named "Debian/GNU Linux's". RedHat made a comparatively much more recent fork. OpenBSD and FreeBSD have their own (different from each other) forks of long standing, too.
Mike Meyer apparently made a GNU cron for the Free Software Foundation in 1987. If it indeed ever existed in the first place, it has since disappeared without a trace.
I provide pre-made service bundles for the nosh toolset for various crons, and I have so far had to make separate ones for Dillon crond, Debian cron, Vixie (a.k.a. ISC or PD) cron, Guenter bcron-{spool,start,update}, Godouet fcron, and OpenBSD cron; because they are significantly different from one another.
In part, this is because although the crontab utility is actually standardized, in the SUS, cron (like many such non-ordinary-user-facing internals) is not standardized. This is actually a good thing, inasmuch as the radically different multiple untrusting dæmons architecture of Guenter bcron would not have been possible if it had had to conform to a standard of one monolithic cron dæmon.
What's that mean though? It's entirely meaningless unless you, what's that, check the manual. Or what if you want it to run on another day? What's that? Check the manual? Sound familiar?
In particular: which day of the week, and at what time?
cron expressions have about as much learning curve as ISO-8601, and are otherwise unambiguous once you know how to read them. systemd's time specifications look like they're full of special cases:
https://www.freedesktop.org/software/systemd/man/systemd.tim...
Why is that simple? Monday isn't even the first day of the week!
But ISO 8601 is the standard so it makes sense to use that.
They also have other desirable behavior like being able to configure it concurrent runs are allowed or if the script should run if the initial date was missed or even restart the job if it fails up to a limit.
It's much more versatile than simply cron, due to that, it's also a lot more useful.
https://www.freebsd.org/cgi/man.cgi?crontab(5) is 1400 or so.
I'd hardly call that impenetrable. Additionally you will note that free bad has an extension to the format for shortcuts like monthly, weekly, &c.
I should note that `man crontab | wc` returns 1680 words while `man systemd.timer | wc` returns 1300 words. Take that for what you while, especially since .timer spends most words on explaining the options instead of the syntax.
I just don't want cron doing randomized delay and repeats. That should functionally be determined by the application.
I think it's perfectly fine that timer does this, it's useful. The applications I run don't support this behaviour out of the box, so why should I have to code up something for each app?
>There's little functional difference between syntax and options in this case,
There is an important difference. The manpage on timers spends most words explaining what exactly each option does and how it can be useful while most of the crontab manpage explains how the syntax works, the options crontab provides are minimal.
?
Cron, busybox and friends are still good things to master.
don't you ? my phone from 2013 runs systemd and wayland.
It's also an extremely niché phone... Witch I seriously wanted to try out, but couldn't because it was actually impossible for me to buy.
It's definitively not representative for phones in general, and certainly not for embedded Linux as a wider term.
Edit: Things might be changing though.
For instance my Netgear NAS used to run a custom Debian-derivative based on Debian 7 (which used sysvinit). But I discoverd today that after some recent updates it's now based on Debian 8 (which ships with systemd instead).
Based on that, I could produce the following plot[1], on a "embedded" device. Which I now know spends a tremendous 42 seconds booting the kernel. I guess it contemplates life, the universe and everything before moving along :)
[1] https://gist.github.com/josteink/3cf87479b97d8ab3eac81cba719...
It has made my life miserable more than once, but looking at how many hours I've spent working around it, I can see why consulting companies love it.
It's also not just a matter of time before everyone switches over, since there's been backlash against systemd and competing projects have either started up, or gained more momentum (except for upstart, obviously!).
One of those alternatives is the "dmd" init system, which seems to have been around for a while but has recently been rebranded as "GNU Shepherd". Shepherd follows the "do one thing well" philosophy, so it only manages daemons. If shepherd users (e.g. GuixSD) want to run scheduled commands, they'll need another program to do that (i.e. a cron daemon), and GNU Mcron looks like a sensible choice since all of these things are configured using Guile Scheme.
As a side rant: I dislike your use of the term "legacy" for something which is actively maintained and gaining users. Usually "legacy" refers to something which is either abandoned, or where the maintainers recommend against adopting it (e.g. "that's our legacy API, use this other one instead"). I think the word "traditional" would work, when talking about cron in general; although Mcron in particular doen't look like a particularly traditional cron (since its selling point is using Scheme for config!)
But seriously though, it solves a lot of problems around dependency and device management, error handling, logging, timer management, and so forth. To be sure, it has a steep learning curve, but I've found the effort invested to be well worth it.
As for the timer functionality in systemd, the configuration language is, IMO, far easier to understand. It doesn't get any easier than:
[Timer]
OnCalendar=weekly
[Timer]
OnStartupSec=0
OnActiveSec=1hYou mean, besides all the highly-available systems on which it currently runs? Since it's already part of the two most-used distributions in the world, it's fair to say that it's gotten sufficient exercise such that all of the serious kinks have been worked out by now.
Also, I'm not sure what you mean by having to "update all the time." Sure, systemd gets occasional security/bugfix patches, but so did sysvinit. And like sysvinit, systemd is hot-reloadable, so it's never been a problem in practice.
take oddjobd for example, which supplants pam_mkhomedir.so in creating a users home directory on first login. oddjob is its own standalone daemon running constantly, while pam_mkhomedir is invoked only as necessary. oddjob needs dbus and systemd to complete what in many systems is just a simple mkhomedir && chown user:grp $homedir. its now fully dependent on the most fundamental building blocks of your OS to do one simple thing.
this also assumes the user doesnt have a home directory...which...many do.
in most commercial infrastructure if you suggest installing oddjobd to handle the potential for a user to log in without their home youll be laughed out of the chat. oddjobd forces organizations back into the 1980s and NIS based implementations of federated authentication where you had to go to a new user machine, or an account creation machine first if you dont want to run yet another idle daemon on your machine
I don't see any of that citation. Or evidence.
Just because you deem something overly complicated doesn't mean that it doesn't serve a practical purpose.
You don't want to go to all the effort to spin up a CPU core to schedule a (cron) process thread, just to find out it has no work to do. Ideally, if you're going to check the time at all, you just want it done in one thread running on one core, so that the rest of the cores can stay asleep and you never have to spend energy context-switching when idle.
That being said, systemd isn't quite the right architecture for getting down to a "tickless everything" system. That'd be something more like WinNT's kernel timer object API, where the kernel sends an event to your window's or service's message inbox to wake you up when the timer is done; or macOS's "Grand Central Dispatch", where any native code (including non-Foundation POSIX code!) can pass scheduling control of any async block through a Mach trap over to one central scheduling process, which coalesces both timers and the runtimes of async events in general so that all background CPU activity happens in bursts with idles in between.
Right now, I am doing this all with a mess of shell scripts (flock + logger + echo calls + pgrep). This is fragile and ugly.
Since systemd provides all of the above easily, a better approach will be one-off systemd jobs. In this case, my crontab entries would be a trivial -- "1 3 * * * root systemctl start cronjob1". This only requires scheduling functionality -- background execution, env vars, email notification and other things no longer matter.
From there, it is just one small step to move scheduling into the init process itself -- after all, compared to what other things init does, scheduling is both simple and safe.
Different tools suit different people. Cron isn't dying any time soon just because the casual Linux user is better served by systemd.
> I can't imagine using a legacy solution anymore.
Good thing sane people are improving on the legacy space then, with mcron--the subject of the link before someone had to mention SystemD--being a case in point.