They have an example service on the website:
(define sshd (service '(sshd ssh-daemon) ;the secure shell daemon #:start (make-inetd-constructor ;start on demand '("/usr/sbin/sshd" "-D" "-i") (list (endpoint (make-socket-address AF_INET INADDR_ANY 22)) (endpoint (make-socket-address AF_INET6 IN6ADDR_ANY 22))) #:max-connections 10) #:stop (make-inetd-destructor) #:respawn? #t)) (register-services (list sshd)) (start-in-the-background '(sshd))Let’s see how the same service looks like with systemd:
[Unit] Description=OpenSSH Daemon Wants=sshdgenkeys.service After=sshdgenkeys.service After=network.target [Service] Type=notify-reload ExecStart=/usr/bin/sshd -D KillMode=process Restart=always [Install] WantedBy=multi-user.targetI have some lisp knowledge, so the scheme version doesn’t look frightening to me, but I guess for sysadmins, who should write these kind of files frequently systemd’s TOML like language is much more easier to understand.
Some differences I see: Shepherd does some firewall management with ports, and I don’t see the services it depends on.
Why this kind of files should be written in a programming language at all? I guess it’s a remnant from the old times, but I like when tools abstract away the programming parts, and users shouldn’t have to deal with that. I like the same thing in docker-compose: I can configure a program whatever language it’s written, I don’t have to deal with what’s happening under the hood.
I guess there is some usefulness with defining services as code, if you need more complex situations, but it should the more rare case nowadays.
For as much as I want to like and learn guix, guile and all that stuff, it’s very very ugly and confusing. I even have a book around for scheme and the parentheses and ’ and # in a bunch of places scare me too much and make no sense.
It’s a system and language that doesn’t work well with more basic editors and tooling and unfortunately for how cool it is I don’t guess it will ever catch on for multiple reasons.
Scheme is just lisp with blackjack and hookers. It has some huge advantages, that’s why it’s called God’s own programming language
It’s older than C, that’s why it doesn’t have C-like syntax like otger common languages
I have some lisp knowledge, so the scheme version doesn’t look frightening to me, but I guess for sysadmins, who should write these kind of files frequently systemd’s TOML like language is much more easier to understand.
People who only know C-style languages tend to struggle with anything that deviates from that too (which is a lot of developers). The Shepard example looks readable to me, but then I’m a Emacs user and have learned a few languages with “weird” syntax so something that looks a bit different is fine.
Why this kind of files should be written in a programming language at all? I guess it’s a remnant from the old times, but I like when tools abstract away the programming parts, and users shouldn’t have to deal with that
It’s user base is akin to the NixOS audience. It’s more aimed at advanced users and sysadmins (with some programming ability) that want to configure their whole system declaratively. Using a real programming language gives a lot of power and flexibility to achieve this that you’d effectively have to create a new language to replicate that (I.e. Nix or Guile).
On the other hand, something like Shepard is potentially overkill for even Nix and Guix. Nix works quite well as a layer on top of systemd to declare a NixOS system, and still gives you enough power to do most things.
a remnant from the old times
This comment demonstrates a misunderstanding of
shepherdandguix. Using an actual programming language vs some bastardized version of a markup language to describe complex configurations is increasingly popular because it is better.guixis inspired bynixand allows you to specify the entire system as code in a reproducible manner - which you don’t want to do in ‘human readable’toml+,yaml+, etc. because it fucking sucks.I like when tools abstract away the programming parts
You can use
schemeto abstract awayschemelol. These are advanced tools for advanced systems.*I use
systemdall the time, but a direct comparison betweensystemdandshepherdwithout additional context is misleading and flawed.Ah right so sherperd is designed for developers and professional sysadmins, and systemd is something that “normal” users (e.g. Ubuntu users) might use?
I’m a developer who does the whole devops thing and I’d consider systemd to be a professional tool with pretty advanced features. My team deploys and operates Kubernetes across tens of thousands of VMs (using our own images, not managed node pools), and all those nodes are using systemd as the foundational service manager.
Shepherd just seems to be another implementation of service management that’s centered around the use of GNU Scheme. I think it’s neat, and it’s far more flexible than systemd units. Flexibility is good, but to much flexibility also lets you build your own footguns. I have no idea if Shepherd lets you build a gun to blow your foot off, so this may not be a concern at all. Scheme is a really powerful language that I know nothing about, so I’m going to assume that the GNU folks are using language features (or the runtime itself) to prevent accidental amputation. The example service looks almost entirely declarative which gives me warm fuzzies.
As an example of something too flexible, just look at old sysvinit scripts. You could do literally anything you wanted because you were just writing Bash. Bash is already the shittiest language in existence and service management is hard, so there were a lot of terribly broken init scripts out there (which is why systemd was created).
From an aesthetic perspective, I do kinda hate Scheme (and the example service by extension). My eyes just do not want to read it, but that’s a personal failing. Many folks love Scheme and lispy languages.
EDIT: I used “Scheme” a lot, but to be technically correct, I should have been saying Guile. It’s GNU’s implementation of Scheme with some nice extensions.
Yeah I didn’t mean to imply systemd wasn’t suitable for professional use, rather that shepherd is only going to be used by people who want to set this up themselves programmatically.
Like how the average computer user is never going to use Nix to install Firefox or whatever.
Like how the average computer user is never going to […] install Firefox or whatever.
Not right know but in 2005-2010 (or something like that), the average user was installing firefox because IE was so bad. It used to be at 80% market share IIRC.
I could see it being nice for software appliances. I spent many years working for a company that made an appliance (run this OVA/stick this pre-imaged box on your network), and they had this godawful mess of perl they used to orchestrate the box (e.g. updating a configuration file from the GUI and then restarting the sysvinit (and later systemd) service). I could see someone writing a system orchestrator in Guile that, rather than shelling out to
systemctl, imports (or whatever it’s called in Scheme) the service definition and directly starts the service using a function call, complete with error handling and all of the nice shit that you don’t get byexecing some binary.libsystemdexists for systemd which lets you have some of the same benefits, but it’s a C library which doesn’t integrate nicely with all languages. I remember not liking any of the Python wrappers I tried, even though Python generally does a great job interfacing with C.
Leave it to the community to do something in Lisp. That language should’ve died 20 years ago.
How is it different to runit or openrc?
It has a different name and is written in Guile
Ok so it’s basically a yet another point of fragmentation. Nice.
And from GNU: https://www.gnu.org/software/shepherd/
To be clear, this is mainly intended to be used with Guix which is a package manager and OS akin to NixOS but written in Guile Scheme.
