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5.11 Invoking guix publish

The purpose of guix publish is to enable users to easily share their store with others, who can then use it as a substitute server (see Substitutes).

When guix publish runs, it spawns an HTTP server which allows anyone with network access to obtain substitutes from it. This means that any machine running Guix can also act as if it were a build farm, since the HTTP interface is compatible with Hydra, the software behind the hydra.gnu.org build farm.

For security, each substitute is signed, allowing recipients to check their authenticity and integrity (see Substitutes). Because guix publish uses the signing key of the system, which is only readable by the system administrator, it must be started as root; the --user option makes it drop root privileges early on.

The signing key pair must be generated before guix publish is launched, using guix archive --generate-key (see Invoking guix archive).

The general syntax is:

guix publish options

Running guix publish without any additional arguments will spawn an HTTP server on port 8080:

guix publish

Once a publishing server has been authorized (see Invoking guix archive), the daemon may download substitutes from it:

guix-daemon --substitute-urls=http://example.org:8080

By default, guix publish compresses archives on the fly as it serves them. This “on-the-fly” mode is convenient in that it requires no setup and is immediately available. However, when serving lots of clients, we recommend using the --cache option, which enables caching of the archives before they are sent to clients—see below for details.

As a bonus, guix publish also serves as a content-addressed mirror for source files referenced in origin records (see origin Reference). For instance, assuming guix publish is running on example.org, the following URL returns the raw hello-2.10.tar.gz file with the given SHA256 hash (represented in nix-base32 format, see Invoking guix hash):

http://example.org/file/hello-2.10.tar.gz/sha256/0ssi1…ndq1i

Obviously, these URLs only work for files that are in the store; in other cases, they return 404 (“Not Found”).

The following options are available:

--port=port
-p port

Listen for HTTP requests on port.

--listen=host

Listen on the network interface for host. The default is to accept connections from any interface.

--user=user
-u user

Change privileges to user as soon as possible—i.e., once the server socket is open and the signing key has been read.

--compression[=level]
-C [level]

Compress data using the given level. When level is zero, disable compression. The range 1 to 9 corresponds to different gzip compression levels: 1 is the fastest, and 9 is the best (CPU-intensive). The default is 3.

Unless --cache is used, compression occurs on the fly and the compressed streams are not cached. Thus, to reduce load on the machine that runs guix publish, it may be a good idea to choose a low compression level, to run guix publish behind a caching proxy, or to use --cache. Using --cache has the advantage that it allows guix publish to add Content-Length HTTP header to its responses.

--cache=directory
-c directory

Cache archives and meta-data (.narinfo URLs) to directory and only serve archives that are in cache.

When this option is omitted, archives and meta-data are created on-the-fly. This can reduce the available bandwidth, especially when compression is enabled, since this may become CPU-bound. Another drawback of the default mode is that the length of archives is not known in advance, so guix publish does not add a Content-Length HTTP header to its responses, which in turn prevents clients from knowing the amount of data being downloaded.

Conversely, when --cache is used, the first request for a store item (via a .narinfo URL) returns 404 and triggers a background process to bake the archive—computing its .narinfo and compressing the archive, if needed. Once the archive is cached in directory, subsequent requests succeed and are served directly from the cache, which guarantees that clients get the best possible bandwidth.

The “baking” process is performed by worker threads. By default, one thread per CPU core is created, but this can be customized. See --workers below.

When --ttl is used, cached entries are automatically deleted when they have expired.

--workers=N

When --cache is used, request the allocation of N worker threads to “bake” archives.

--ttl=ttl

Produce Cache-Control HTTP headers that advertise a time-to-live (TTL) of ttl. ttl must denote a duration: 5d means 5 days, 1m means 1 month, and so on.

This allows the user’s Guix to keep substitute information in cache for ttl. However, note that guix publish does not itself guarantee that the store items it provides will indeed remain available for as long as ttl.

Additionally, when --cache is used, cached entries that have not been accessed for ttl may be deleted.

--nar-path=path

Use path as the prefix for the URLs of “nar” files (see normalized archives).

By default, nars are served at a URL such as /nar/gzip/…-coreutils-8.25. This option allows you to change the /nar part to path.

--public-key=file
--private-key=file

Use the specific files as the public/private key pair used to sign the store items being published.

The files must correspond to the same key pair (the private key is used for signing and the public key is merely advertised in the signature metadata). They must contain keys in the canonical s-expression format as produced by guix archive --generate-key (see Invoking guix archive). By default, /etc/guix/signing-key.pub and /etc/guix/signing-key.sec are used.

--repl[=port]
-r [port]

Spawn a Guile REPL server (see REPL Servers in GNU Guile Reference Manual) on port (37146 by default). This is used primarily for debugging a running guix publish server.

Enabling guix publish on a GuixSD system is a one-liner: just instantiate a guix-publish-service-type service in the services field of the operating-system declaration (see guix-publish-service-type).

If you are instead running Guix on a “foreign distro”, follow these instructions:”


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