move stuff about implementing modules/services into Developer manual
This commit is contained in:
parent
b3f0c33347
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@ -112,7 +112,7 @@ check" command at regular intervals. When the health check fails,
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indicating that the wrapped service is not working, it is terminated and
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allowed to restart.
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==== Runtime secrets (external vault)
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=== Runtime secrets (external vault)
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Secrets (such as wifi passphrases, PPP username/password, SSH keys, etc)
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that you provide as literal values in `+configuration.nix+` are
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@ -221,250 +221,3 @@ directly on the device. (That latter approach may pose a chicken/egg
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problem if the device needs secrets to boot up and run the services you
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are relying on in order to login).
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==== Writing services
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For the most part, for common use cases, hopefully the services you need
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will be defined by modules and you will only have to pass the right
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parameters to `+build+`.
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Should you need to create a custom service of your own devising, use the
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[.title-ref]#oneshot# or [.title-ref]#longrun# functions:
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* a "longrun" service is the "normal" service concept: it has a `+run+`
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action which describes the process to start, and it watches that process
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to restart it if it exits. The process should not attempt to daemonize
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or "background" itself, otherwise s6-rc will think it died. Whatever it
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prints to standard output/standard error will be logged.
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[source,nix]
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----
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config.services.cowsayd = pkgs.liminix.services.longrun {
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name = "cowsayd";
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run = "${pkgs.cowsayd}/bin/cowsayd --port 3001 --breed hereford";
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# don't start this until the lan interface is ready
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dependencies = [ config.services.lan ];
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}
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----
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* a "oneshot" service doesn't have a process attached. It consists of
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`+up+` and `+down+` actions which are bits of shell script that are run
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at the appropriate points in the service lifecycle
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[source,nix]
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----
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config.services.greenled = pkgs.liminix.services.oneshot {
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name = "greenled";
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up = ''
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echo 17 > /sys/class/gpio/export
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echo out > /sys/class/gpio/gpio17/direction
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echo 0 > /sys/class/gpio/gpio17/value
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'';
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down = ''
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echo 0 > /sys/class/gpio/gpio17/value
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'';
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}
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----
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Services may have dependencies: as you see above in the `+cowsayd+`
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example, it depends on some service called `+config.services.lan+`,
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meaning that it won't be started until that other service is up.
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==== Service outputs
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Outputs are a mechanism by which a service can provide data which may be
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required by other services. For example:
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* the DHCP client service can expect to receive nameserver address
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information as one of the fields in the response from the DHCP server:
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we provide that as an output which a dependent service for a stub name
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resolver can use to configure its upstream servers.
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* a service that creates a new network interface (e.g. ppp) will provide
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the name of the interface (`+ppp0+`, or `+ppp1+` or `+ppp7+`) as an
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output so that a dependent service can reference it to set up a route,
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or to configure firewall rules.
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A service `+myservice+` should write its outputs as files in
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`+/run/services/outputs/myservice+`: you can look around this directory
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on a running Liminix system to see how it's used currently. Usually we
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use the `+in_outputs+` shell function in the `+up+` or `+run+`
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attributes of the service:
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[source,shell]
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----
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(in_outputs ${name}
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for i in lease mask ip router siaddr dns serverid subnet opt53 interface ; do
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(printenv $i || true) > $i
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done)
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----
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The outputs are just files, so technically you can read them using
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anything that can read a file. Liminix has two "preferred" mechanisms,
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though:
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===== One-off lookups
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In any context that ends up being evaluated by the shell, use `+output+`
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to print the value of an output
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[source,nix]
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----
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services.defaultroute4 = svc.network.route.build {
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via = "$(output ${services.wan} address)";
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target = "default";
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dependencies = [ services.wan ];
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};
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----
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===== Continuous updates
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The downside of using shell functions in downstream service startup
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scripts is that they only run when the service starts up: if a service
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output _changes_, the downstream service would have to be restarted to
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notice the change. Sometimes this is OK but other times the downstream
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has no other need to restart, if it can only get its new data.
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For this case, there is the `+anoia.svc+` Fennel library, which allows
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you to write a simple loop which is iterated over whenever a service's
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outputs change. This code is from
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`+modules/dhcp6c/acquire-wan-address.fnl+`
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[source,fennel]
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----
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(fn update-addresses [wan-device addresses new-addresses exec]
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;; run some appropriate "ip address [add|remove]" commands
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)
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(fn run []
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(let [[state-directory wan-device] arg
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dir (svc.open state-directory)]
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(accumulate [addresses []
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v (dir:events)]
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(update-addresses wan-device addresses
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(or (v:output "address") []) system))))
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----
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The `+output+` method seen here accepts a filename (relative to the
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service's output directory), or a directory name. It returns the first
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line of that file, or for directories it returns a table (Lua's
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key/value datastructure, similar to a hash/dictionary) of the outputs in
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that directory.
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===== Output design considerations
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For preference, outputs should be short and simple, and not require
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downstream services to do complicated parsing in order to use them.
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Shell commands in Liminix are run using the Busybox shell which doesn't
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have the niceties of an advanced shell like Bash let alone those of a
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real programming language.
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Note also that the Lua `+svc+` library only reads the first line of each
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output.
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=== Module implementation
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Modules in Liminix conventionally live in
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`+modules/somename/default.nix+`. If you want or need to write your own,
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you may wish to refer to the examples there in conjunction with reading
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this section.
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A module is a function that accepts `+{lib, pkgs, config, ... }+` and
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returns an attrset with keys `+imports, options config+`.
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* `+imports+` is a list of paths to the other modules required by this
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one
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* `+options+` is a nested set of option declarations
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* `+config+` is a nested set of option definitions
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The NixOS manual section
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https://nixos.org/manual/nixos/stable/#sec-writing-modules[Writing NixOS
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Modules] is a quite comprehensive reference to writing NixOS modules,
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which is also mostly applicable to Liminix except that it doesn't cover
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service templates.
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==== Service templates
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To expose a service template in a module, it needs the following:
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* an option declaration for `+system.service.myservicename+` with the
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type of `+liminix.lib.types.serviceDefn+`
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[source,nix]
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----
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options = {
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system.service.cowsay = mkOption {
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type = liminix.lib.types.serviceDefn;
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};
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};
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----
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* an option definition for the same key, which specifies where to import
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the service template from (often `+./service.nix+`) and the types of its
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parameters.
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[source,nix]
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----
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config.system.service.cowsay = config.system.callService ./service.nix {
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address = mkOption {
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type = types.str;
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default = "0.0.0.0";
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description = "Listen on specified address";
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example = "127.0.0.1";
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};
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port = mkOption {
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type = types.port;
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default = 22;
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description = "Listen on specified TCP port";
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};
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breed = mkOption {
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type = types.str;
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default = "British Friesian"
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description = "Breed of the cow";
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};
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};
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----
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Then you need to provide the service template itself, probably in
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`+./service.nix+`:
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[source,nix]
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----
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{
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# any nixpkgs package can be named here
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liminix
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, cowsayd
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, serviceFns
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, lib
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}:
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# these are the parameters declared in the callService invocation
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{ address, port, breed} :
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let
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inherit (liminix.services) longrun;
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inherit (lib.strings) escapeShellArg;
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in longrun {
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name = "cowsayd";
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run = "${cowsayd}/bin/cowsayd --address ${address} --port ${builtins.toString port} --breed ${escapeShellArg breed}";
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}
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----
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[TIP]
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====
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Not relevant to module-based services specifically, but a common gotcha
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when specifiying services is forgetting to transform "rich" parameter
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values into text when composing a command for the shell to execute. Note
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here that the port number, an integer, is stringified with `+toString+`,
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and the name of the breed, which may contain spaces, is escaped with
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`+escapeShellArg+`
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====
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==== Types
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All of the NixOS module types are available in Liminix. These
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Liminix-specific types also exist in `+pkgs.liminix.lib.types+`:
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* `+service+`: an s6-rc service
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* `+interface+`: an s6-rc service which specifies a network interface
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* `+serviceDefn+`: a service "template" definition
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In the future it is likely that we will extend this to include other
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useful types in the networking domain: for example; IP address, network
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prefix or netmask, protocol family and others as we find them.
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|
@ -1,124 +1,287 @@
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= For Developers
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== Contributing
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In any Nix-based system the line between "configuration"
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and "development" is less of a line and more of a continuum.
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This section covers some topics further towards the latter end.
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Patches welcome! Also bug reports, documentation improvements,
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experience reports/case studies etc etc all equally as welcome.
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== Writing modules and services
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* if you have an obvious bug fix, new package, documentation
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improvement or other uncontroversial small patch, send it straight
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in.
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It helps here to know NixOS! Liminix uses the NixOS module
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infrastructure code, meaning that everything that has been written for
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NixOS about the syntax, the type system, and the rules for combining
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configuration values from different sources is just as applicable
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here.
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* if you have a large new feature or design change in mind, please
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please _get in touch_ to talk about it before you commit time to
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implementing it. Perhaps it isn't what we were expecting, almost
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certainly we will have ideas or advice on what it should do or how
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it should be done.
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=== Services
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Liminix development is not tied to Github or any other particular
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forge. How to send changes:
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For the most part, for common use cases, we hope that Liminix modules
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provide service templates for all the services you will need, and you
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will only have to pass the right parameters to `+build+`.
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1. Push your Liminix repo with your changes to a git repository
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somewhere on the Internet that I can clone from. It can be on Codeberg
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or Gitlab or Sourcehut or Forgejo or Gitea or Github or a bare repo in
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your own personal web space or any kind of hosting you like.
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But if you're reading this then our hopes are in vain. To create a
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custom service of your own devising, use the [.title-ref]#oneshot# or
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[.title-ref]#longrun# functions:
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2. Email devel@liminix.org with the URL of the repo and the branch
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name. And/or put it on the IRC channel if you prefer, as long as you
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make sure someone who can merge it has seen your message.
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* a "longrun" service is the "normal" service concept: it has a `+run+`
|
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action which describes the process to start, and it watches that process
|
||||
to restart it if it exits. The process should not attempt to daemonize
|
||||
or "background" itself, otherwise s6-rc will think it died. Whatever it
|
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prints to standard output/standard error will be logged.
|
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|
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If that's not an option, I’m also happy for you to send your changes
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direct to the list itself, as an incremental git bundle or using git
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format-patch. We'll work it out somehow.
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[source,nix]
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----
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config.services.cowsayd = pkgs.liminix.services.longrun {
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name = "cowsayd";
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run = "${pkgs.cowsayd}/bin/cowsayd --port 3001 --breed hereford";
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# don't start this until the lan interface is ready
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dependencies = [ config.services.lan ];
|
||||
}
|
||||
----
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The main development repo for Liminix is hosted at
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<https://gti.telent.net/dan/liminix>, with a read-only mirror at
|
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<https://github.com/telent/liminix>. If you're happy to use Github
|
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then you can fork from the latter to make your changes, but please use
|
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the mailing list one of the approved routes to tell me about your changes because I
|
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don't regularly check PRs.
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* a "oneshot" service doesn't have a process attached. It consists of
|
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`+up+` and `+down+` actions which are bits of shell script that are run
|
||||
at the appropriate points in the service lifecycle
|
||||
|
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Remember that the <<_code_of_conduct>> applies to all Liminix spaces,
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and anyone who violates it may be sanctioned or expelled from these
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spaces at the discretion of the project leadership.
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[source,nix]
|
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----
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config.services.greenled = pkgs.liminix.services.oneshot {
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name = "greenled";
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up = ''
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echo 17 > /sys/class/gpio/export
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echo out > /sys/class/gpio/gpio17/direction
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echo 0 > /sys/class/gpio/gpio17/value
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'';
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down = ''
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echo 0 > /sys/class/gpio/gpio17/value
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'';
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}
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----
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=== Nix language style
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Services may have dependencies: as you see above in the `+cowsayd+`
|
||||
example, it depends on some service called `+config.services.lan+`,
|
||||
meaning that it won't be started until that other service is up.
|
||||
|
||||
This section describes some Nix language style points that we attempt to
|
||||
adhere to in this repo. Some are more aspirational than actual.
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===== Service outputs
|
||||
|
||||
* indentation and style is according to `nixfmt-rfc-style`
|
||||
* favour `+callPackage+` over raw `+import+` for calling derivations or
|
||||
any function that may generate one - any code that might need `+pkgs+`
|
||||
or parts of it.
|
||||
* prefer `+let inherit (quark) up down strange charm+` over
|
||||
`+with quark+`, in any context where the scope is more than a single
|
||||
expression or there is more than one reference to `+up+`, `+down+` etc.
|
||||
`+with pkgs; [ foo bar baz]+` is OK,
|
||||
`+with lib; stdenv.mkDerivation { ... }+` is usually not.
|
||||
* `+<liminix>+` is defined only when running tests, so don't refer to it
|
||||
in "application" code
|
||||
* the parameters to a derivation are sorted alphabetically, except for
|
||||
`+lib+`, `+stdenv+` and maybe other non-package "special cases"
|
||||
* where a `+let+` form defines multiple names, put a newline after the
|
||||
token `+let+`, and indent each name two characters
|
||||
* to decide whether some code should be a package or a module? Packages
|
||||
are self-contained - they live in `+/nix/store/eeeeeee-name+` and don't
|
||||
directly change system behaviour by their presence or absense. modules
|
||||
can add to `+/etc+` or `+/bin+` or other global state, create services,
|
||||
all that side-effecty stuff. Generally it should be a package unless it
|
||||
can't be.
|
||||
Outputs are a mechanism by which a service can provide data which may be
|
||||
required by other services. For example:
|
||||
|
||||
=== Copyright
|
||||
* the DHCP client service can expect to receive nameserver address
|
||||
information as one of the fields in the response from the DHCP server:
|
||||
we provide that as an output which a dependent service for a stub name
|
||||
resolver can use to configure its upstream servers.
|
||||
* a service that creates a new network interface (e.g. ppp) will provide
|
||||
the name of the interface (`+ppp0+`, or `+ppp1+` or `+ppp7+`) as an
|
||||
output so that a dependent service can reference it to set up a route,
|
||||
or to configure firewall rules.
|
||||
|
||||
The Nix code in Liminix is MIT-licenced (same as Nixpkgs), but the code
|
||||
it combines from other places (e.g. Linux, OpenWrt) may have a variety
|
||||
of licences. Copyright assignment is not expected:
|
||||
just like when submitting to the Linux kernel you retain the copyright
|
||||
on the code you contribute.
|
||||
A service `+myservice+` should write its outputs as files in
|
||||
`+/run/services/outputs/myservice+`: you can look around this directory
|
||||
on a running Liminix system to see how it's used currently. Usually we
|
||||
use the `+in_outputs+` shell function in the `+up+` or `+run+`
|
||||
attributes of the service:
|
||||
|
||||
=== Automated builds
|
||||
[source,shell]
|
||||
----
|
||||
(in_outputs ${name}
|
||||
for i in lease mask ip router siaddr dns serverid subnet opt53 interface ; do
|
||||
(printenv $i || true) > $i
|
||||
done)
|
||||
----
|
||||
|
||||
Automated builds are run on each push to the main branch. This tests
|
||||
that (among other things)
|
||||
The outputs are just files, so technically you can read them using
|
||||
anything that can read a file. Liminix has two "preferred" mechanisms,
|
||||
though:
|
||||
|
||||
* every device image builds
|
||||
* the build for the “qemu” target is executed with a fake network upstream to test
|
||||
* PPPoE and DHCP service
|
||||
* hostap (wireless gateway)
|
||||
===== One-off lookups
|
||||
|
||||
You can view the build output at https://build.liminix.org . The tests
|
||||
are defined in ci.nix.
|
||||
In any context that ends up being evaluated by the shell, use `+output+`
|
||||
to print the value of an output
|
||||
|
||||
Unfortunately there's no (easy) way I can make _my_ CI infrastructure
|
||||
run _your_ code, other than merging it. But see <<_running_tests>>
|
||||
for how to exercise the same code locally on your machine.
|
||||
[source,nix]
|
||||
----
|
||||
services.defaultroute4 = svc.network.route.build {
|
||||
via = "$(output ${services.wan} address)";
|
||||
target = "default";
|
||||
dependencies = [ services.wan ];
|
||||
};
|
||||
----
|
||||
|
||||
===== Continuous updates
|
||||
|
||||
The downside of using shell functions in downstream service startup
|
||||
scripts is that they only run when the service starts up: if a service
|
||||
output _changes_, the downstream service would have to be restarted to
|
||||
notice the change. Sometimes this is OK but other times the downstream
|
||||
has no other need to restart, if it can only get its new data.
|
||||
|
||||
For this case, there is the `+anoia.svc+` Fennel library, which allows
|
||||
you to write a simple loop which is iterated over whenever a service's
|
||||
outputs change. This code is from
|
||||
`+modules/dhcp6c/acquire-wan-address.fnl+`
|
||||
|
||||
[source,fennel]
|
||||
----
|
||||
(fn update-addresses [wan-device addresses new-addresses exec]
|
||||
;; run some appropriate "ip address [add|remove]" commands
|
||||
)
|
||||
|
||||
(fn run []
|
||||
(let [[state-directory wan-device] arg
|
||||
dir (svc.open state-directory)]
|
||||
(accumulate [addresses []
|
||||
v (dir:events)]
|
||||
(update-addresses wan-device addresses
|
||||
(or (v:output "address") []) system))))
|
||||
----
|
||||
|
||||
The `+output+` method seen here accepts a filename (relative to the
|
||||
service's output directory), or a directory name. It returns the first
|
||||
line of that file, or for directories it returns a table (Lua's
|
||||
key/value datastructure, similar to a hash/dictionary) of the outputs in
|
||||
that directory.
|
||||
|
||||
===== Design considerations for outputs
|
||||
|
||||
For preference, outputs should be short and simple, and not require
|
||||
downstream services to do complicated parsing in order to use them.
|
||||
Shell commands in Liminix are run using the Busybox shell which doesn't
|
||||
have the niceties evel of an advanced shell like Bash, let alone those of a
|
||||
real programming language.
|
||||
|
||||
Note also that the Lua `+svc+` library only reads the first line of each
|
||||
output.
|
||||
|
||||
|
||||
== Development tools
|
||||
=== Modules
|
||||
|
||||
In this section we describe some tools to make the edit/build/run
|
||||
development cycle less painful than flashing a new image on a hardware
|
||||
device every time.
|
||||
Modules in Liminix conventionally live in
|
||||
`+modules/somename/default.nix+`. If you want or need to write your own,
|
||||
you may wish to refer to the examples there in conjunction with reading
|
||||
this section.
|
||||
|
||||
A module is a function that accepts `+{lib, pkgs, config, ... }+` and
|
||||
returns an attrset with keys `+imports, options, config+`.
|
||||
|
||||
* `+imports+` is a list of paths to the other modules required by this
|
||||
one
|
||||
* `+options+` is a nested set of option declarations
|
||||
* `+config+` is a nested set of option definitions
|
||||
|
||||
The NixOS manual section
|
||||
https://nixos.org/manual/nixos/stable/#sec-writing-modules[Writing NixOS
|
||||
Modules] is a quite comprehensive reference to writing NixOS modules,
|
||||
which is also mostly applicable to Liminix except that it doesn't cover
|
||||
service templates.
|
||||
|
||||
|
||||
==== Service templates
|
||||
|
||||
Although you can define services "ad hoc" using `longrun` or `oneshot`
|
||||
<<_writing_services,as above>>, this approach has limitations if
|
||||
you're writing code intended for wider use. Services in the
|
||||
modules bundled with Liminix are implemented following a pattern we
|
||||
call "service templates": functions that accept a _type-checked_
|
||||
attrset and return an appropriately configured service that can be
|
||||
assigned by the caller to a key in ``config.services``.
|
||||
|
||||
To expose a service template in a module, it needs the following:
|
||||
|
||||
* an option declaration for `+system.service.myservicename+` with the
|
||||
type of `+liminix.lib.types.serviceDefn+`
|
||||
|
||||
[source,nix]
|
||||
----
|
||||
options = {
|
||||
system.service.cowsay = mkOption {
|
||||
type = liminix.lib.types.serviceDefn;
|
||||
};
|
||||
};
|
||||
----
|
||||
|
||||
* an option definition for the same key, which specifies where to import
|
||||
the service template from (often `+./service.nix+`) and the types of its
|
||||
parameters.
|
||||
|
||||
[source,nix]
|
||||
----
|
||||
config.system.service.cowsay = config.system.callService ./service.nix {
|
||||
address = mkOption {
|
||||
type = types.str;
|
||||
default = "0.0.0.0";
|
||||
description = "Listen on specified address";
|
||||
example = "127.0.0.1";
|
||||
};
|
||||
port = mkOption {
|
||||
type = types.port;
|
||||
default = 22;
|
||||
description = "Listen on specified TCP port";
|
||||
};
|
||||
breed = mkOption {
|
||||
type = types.str;
|
||||
default = "British Friesian"
|
||||
description = "Breed of the cow";
|
||||
};
|
||||
};
|
||||
----
|
||||
|
||||
Then you need to provide the service template itself, probably in
|
||||
`+./service.nix+`:
|
||||
|
||||
[source,nix]
|
||||
----
|
||||
{
|
||||
# any nixpkgs package can be named here
|
||||
liminix
|
||||
, cowsayd
|
||||
, serviceFns
|
||||
, lib
|
||||
}:
|
||||
# these are the parameters declared in the callService invocation
|
||||
{ address, port, breed} :
|
||||
let
|
||||
inherit (liminix.services) longrun;
|
||||
inherit (lib.strings) escapeShellArg;
|
||||
in longrun {
|
||||
name = "cowsayd";
|
||||
run = "${cowsayd}/bin/cowsayd --address ${address} --port ${builtins.toString port} --breed ${escapeShellArg breed}";
|
||||
}
|
||||
----
|
||||
|
||||
TIP: Not relevant to module-based services specifically, but a common gotcha
|
||||
when specifiying services is forgetting to transform "rich" parameter
|
||||
values into text when composing a command for the shell to execute. Note
|
||||
here that the port number, an integer, is stringified with `+toString+`,
|
||||
and the name of the breed, which may contain spaces, is escaped with
|
||||
`+escapeShellArg+`
|
||||
|
||||
=== Types
|
||||
|
||||
All of the NixOS module types are available in Liminix. These
|
||||
Liminix-specific types also exist in `+pkgs.liminix.lib.types+`:
|
||||
|
||||
* `+service+`: an s6-rc service
|
||||
* `+interface+`: an s6-rc service which specifies a network interface
|
||||
* `+serviceDefn+`: a service "template" definition
|
||||
|
||||
In the future it is likely that we will extend this to include other
|
||||
useful types in the networking domain: for example; IP address, network
|
||||
prefix or netmask, protocol family and others as we find them.
|
||||
|
||||
// FIXME if this is still true we should fix it
|
||||
In general, packages and tools that run on the "build" machine are
|
||||
available in the `+buildEnv+` derivation and can most easily be added to
|
||||
your environment by running `+nix-shell+`.
|
||||
|
||||
=== Emulated devices
|
||||
|
||||
Liminix has a number of emulated device descriptions which generate
|
||||
images suitable for running on your build machine using the free
|
||||
Unless your changes depend on particular hardware devices, you may
|
||||
want to test your new/changed module with one of the emulated
|
||||
"devices" which runn on your build machine using the free
|
||||
http://www.qemu.org[QEMU machine emulator]. They are
|
||||
|
||||
* `qemu`(MIPS)
|
||||
* `qemu-armv7l`(32 bit ARM)
|
||||
* `qemu-aarch64` (64 bit ARM)
|
||||
|
||||
This is useful for developing userland without needing to keep
|
||||
flashing or messing with U-Boot: it also enables testing against
|
||||
emulated network peers using
|
||||
This means you don't need to keep flashing or messing with U-Boot: it
|
||||
also enables testing against emulated network peers using
|
||||
https://wiki.qemu.org/Documentation/Networking#Socket[QEMU socket
|
||||
networking], which may be preferable to letting Liminix loose on your
|
||||
actual LAN. To build,
|
||||
@ -143,7 +306,7 @@ connect-vm+` to connect to either of these sockets, and ^O to
|
||||
disconnect.
|
||||
|
||||
[[qemu-networking]]
|
||||
==== Networking
|
||||
===== Networking
|
||||
|
||||
VMs can network with each other using QEMU socket networking. We observe
|
||||
these conventions, so that we can run multiple emulated instances and
|
||||
@ -158,7 +321,7 @@ Any VM started by a `+run.sh+` script is connected to "lan" and
|
||||
"access". The emulated upstream (see below) runs PPPoE and is
|
||||
connected to "access" and "world".
|
||||
|
||||
==== Upstream connection
|
||||
===== Upstream connection
|
||||
|
||||
In pkgs/routeros there is a derivation to install and configure
|
||||
https://mikrotik.com/software[Mikrotik RouterOS] as a PPPoE access
|
||||
@ -186,9 +349,11 @@ own responsibility if you use this to ensure you're compliant with the
|
||||
terms of Mikrotik's licencing. It may be supplemented or replaced in
|
||||
time with configurations for RP-PPPoE and/or Accel PPP.#
|
||||
|
||||
=== Hardware devices
|
||||
== Hardware hacking/porting to new device
|
||||
|
||||
==== TFTP
|
||||
Coming soon
|
||||
|
||||
=== TFTP
|
||||
|
||||
[[tftpserver]]
|
||||
How you get your image onto hardware will vary according to the device,
|
||||
@ -238,7 +403,7 @@ to copy-paste the whole of `+boot.scr+` into a terminal emulator and
|
||||
have it work just like that. You may need to paste each line one at a
|
||||
time, or even retype it.
|
||||
|
||||
==== Running from RAM
|
||||
=== Running from RAM
|
||||
|
||||
For a faster edit-compile-test cycle, you can build a TFTP-bootable
|
||||
image which boots directly from RAM (using phram) instead of needing
|
||||
@ -256,7 +421,7 @@ transfer the kernel and filesystem over TFTP and boot the kernel from
|
||||
RAM.
|
||||
|
||||
[[bng]]
|
||||
==== Networking
|
||||
=== Networking
|
||||
|
||||
You probably don't want to be testing a device that might serve DHCP,
|
||||
DNS and routing protocols on the same LAN as you (or your colleagues,
|
||||
@ -322,6 +487,99 @@ NOTE: If you make changes to the bordervm configuration after executing
|
||||
`+run-border-vm+`, you need to remove the `+border.qcow2+` disk image
|
||||
file otherwise the changes won't get picked up.
|
||||
|
||||
== Contributing
|
||||
|
||||
Patches welcome! Also bug reports, documentation improvements,
|
||||
experience reports/case studies etc etc all equally as welcome.
|
||||
|
||||
* if you have an obvious bug fix, new package, documentation
|
||||
improvement or other uncontroversial small patch, send it straight
|
||||
in.
|
||||
|
||||
* if you have a large new feature or design change in mind, please
|
||||
please _get in touch_ to talk about it before you commit time to
|
||||
implementing it. Perhaps it isn't what we were expecting, almost
|
||||
certainly we will have ideas or advice on what it should do or how
|
||||
it should be done.
|
||||
|
||||
Liminix development is not tied to Github or any other particular
|
||||
forge. How to send changes:
|
||||
|
||||
1. Push your Liminix repo with your changes to a git repository
|
||||
somewhere on the Internet that I can clone from. It can be on Codeberg
|
||||
or Gitlab or Sourcehut or Forgejo or Gitea or Github or a bare repo in
|
||||
your own personal web space or any kind of hosting you like.
|
||||
|
||||
2. Email devel@liminix.org with the URL of the repo and the branch
|
||||
name, and we will take a look.
|
||||
|
||||
If that's not an option, I’m also happy for you to send your changes
|
||||
direct to the list itself, as an incremental git bundle or using git
|
||||
format-patch. We'll work it out somehow.
|
||||
|
||||
The main development repo for Liminix is hosted at
|
||||
<https://gti.telent.net/dan/liminix>, with a read-only mirror at
|
||||
<https://github.com/telent/liminix>. If you're happy to use Github
|
||||
then you can fork from the latter to make your changes, but please use
|
||||
the mailing list one of the approved routes to tell me about your changes because I don't regularly go there to check PRs.
|
||||
|
||||
Remember that the <<_code_of_conduct>> applies to all Liminix spaces,
|
||||
and anyone who violates it may be sanctioned or expelled from these
|
||||
spaces at the discretion of the project leadership.
|
||||
|
||||
=== Nix language style
|
||||
|
||||
This section describes some Nix language style points that we attempt to
|
||||
adhere to in this repo. Some are more aspirational than actual.
|
||||
|
||||
* indentation and style is according to `nixfmt-rfc-style`
|
||||
* favour `+callPackage+` over raw `+import+` for calling derivations or
|
||||
any function that may generate one - any code that might need `+pkgs+`
|
||||
or parts of it.
|
||||
* prefer `+let inherit (quark) up down strange charm+` over
|
||||
`+with quark+`, in any context where the scope is more than a single
|
||||
expression or there is more than one reference to `+up+`, `+down+` etc.
|
||||
`+with pkgs; [ foo bar baz]+` is OK,
|
||||
`+with lib; stdenv.mkDerivation { ... }+` is usually not.
|
||||
* `+<liminix>+` is defined only when running tests, so don't refer to it
|
||||
in "application" code
|
||||
* the parameters to a derivation are sorted alphabetically, except for
|
||||
`+lib+`, `+stdenv+` and maybe other non-package "special cases"
|
||||
* where a `+let+` form defines multiple names, put a newline after the
|
||||
token `+let+`, and indent each name two characters
|
||||
* to decide whether some code should be a package or a module? Packages
|
||||
are self-contained - they live in `+/nix/store/eeeeeee-name+` and don't
|
||||
directly change system behaviour by their presence or absense. modules
|
||||
can add to `+/etc+` or `+/bin+` or other global state, create services,
|
||||
all that side-effecty stuff. Generally it should be a package unless it
|
||||
can't be.
|
||||
|
||||
=== Copyright
|
||||
|
||||
The Nix code in Liminix is MIT-licenced (same as Nixpkgs), but the code
|
||||
it combines from other places (e.g. Linux, OpenWrt) may have a variety
|
||||
of licences. Copyright assignment is not expected:
|
||||
just like when submitting to the Linux kernel you retain the copyright
|
||||
on the code you contribute.
|
||||
|
||||
=== Automated builds
|
||||
|
||||
Automated builds are run on each push to the main branch. This tests
|
||||
that (among other things)
|
||||
|
||||
* every device image builds
|
||||
* the build for the “qemu” target is executed with a fake network upstream to test
|
||||
* PPPoE and DHCP service
|
||||
* hostap (wireless gateway)
|
||||
|
||||
You can view the build output at https://build.liminix.org . The tests
|
||||
are defined in ci.nix.
|
||||
|
||||
Unfortunately there's no (easy) way I can make _my_ CI infrastructure
|
||||
run _your_ code, other than merging it. But see <<_running_tests>>
|
||||
for how to exercise the same code locally on your machine.
|
||||
|
||||
|
||||
== Running tests
|
||||
|
||||
You can run all of the tests by evaluating `+ci.nix+`, which is the
|
||||
@ -333,12 +591,6 @@ nix-build -I liminix=`pwd` ci.nix -A pppoe # run one job
|
||||
nix-build -I liminix=`pwd` ci.nix -A all # run all jobs
|
||||
----
|
||||
|
||||
== Porting to new hardware
|
||||
|
||||
// FIXME add this
|
||||
|
||||
TBD
|
||||
|
||||
== Troubleshooting
|
||||
|
||||
=== Diagnosing unexpectedly large images
|
||||
|
Loading…
Reference in New Issue
Block a user