Taskserver is the server component of Taskwarrior, a free and open source todo list application. Upstream documentation:

Taskserver does all of its authentication via TLS using client certificates, so you either need to roll your own CA or purchase a certificate from a known CA, which allows creation of client certificates. These certificates are usually advertised as server certificates. So in order to make it easier to handle your own CA, there is a helper tool called nixos-taskserver which manages the custom CA along with Taskserver organisations, users and groups. While the client certificates in Taskserver only authenticate whether a user is allowed to connect, every user has its own UUID which identifies it as an entity. With nixos-taskserver the client certificate is created along with the UUID of the user, so it handles all of the credentials needed in order to setup the Taskwarrior client to work with a Taskserver.

Because Taskserver by default only provides scripts to setup users imperatively, the nixos-taskserver tool is used for addition and deletion of organisations along with users and groups defined by and as well for imperative set up. The tool is designed to not interfere if the command is used to manually set up some organisations, users or groups. For example if you add a new organisation using nixos-taskserver org add foo, the organisation is not modified and deleted no matter what you define in services.taskserver.organisations, even if you're adding the same organisation in that option. The tool is modelled to imitate the official taskd command, documentation for each subcommand can be shown by using the --help switch.

Everything is done according to what you specify in the module options, however in order to set up a Taskwarrior client for synchronisation with a Taskserver instance, you have to transfer the keys and certificates to the client machine. This is done using nixos-taskserver user export $orgname $username which is printing a shell script fragment to stdout which can either be used verbatim or adjusted to import the user on the client machine. For example, let's say you have the following configuration: { = true; = "server"; = "::"; services.taskserver.organisations.my-company.users = [ "alice" ]; } This creates an organisation called my-company with the user alice. Now in order to import the alice user to another machine alicebox, all we need to do is something like this: $ ssh server nixos-taskserver user export my-company alice | sh Of course, if no SSH daemon is available on the server you can also copy & paste it directly into a shell. After this step the user should be set up and you can start synchronising your tasks for the first time with task sync init on alicebox. Subsequent synchronisation requests merely require the command task sync after that stage.

If you set any options within service.taskserver.pki.manual.*, nixos-taskserver won't issue certificates, but you can still use it for adding or removing user accounts.