---

10.3 Invoking guix download

When writing a package definition, developers typically need to download a source tarball, compute its SHA256 hash, and write that hash in the package definition (see Defining Packages). The guix download tool helps with this task: it downloads a file from the given URI, adds it to the store, and prints both its file name in the store and its SHA256 hash.

The fact that the downloaded file is added to the store saves bandwidth: when the developer eventually tries to build the newly defined package with guix build, the source tarball will not have to be downloaded again because it is already in the store. It is also a convenient way to temporarily stash files, which may be deleted eventually (see Invoking guix gc).

The guix download command supports the same URIs as used in package definitions. In particular, it supports mirror:// URIs. https URIs (HTTP over TLS) are supported provided the Guile bindings for GnuTLS are available in the user’s environment; when they are not available, an error is raised. See how to install the GnuTLS bindings for Guile in GnuTLS-Guile, for more information.

guix download verifies HTTPS server certificates by loading the certificates of X.509 authorities from the directory pointed to by the SSL_CERT_DIR environment variable (see X.509 Certificates), unless --no-check-certificate is used.

The following options are available:

--hash=algorithm

-H algorithm

Compute a hash using the specified algorithm. See Invoking guix hash, for more information.

--format=fmt

-f fmt

Write the hash in the format specified by fmt. For more information on the valid values for fmt, see Invoking guix hash.

--no-check-certificate

Do not validate the X.509 certificates of HTTPS servers.

When using this option, you have absolutely no guarantee that you are communicating with the authentic server responsible for the given URL, which makes you vulnerable to “man-in-the-middle” attacks.

--output=file

-o file

Save the downloaded file to file instead of adding it to the store.