diff --git a/doc/manual/nix-prefetch-url.xml b/doc/manual/nix-prefetch-url.xml index a6b3711e3..a0d5a97f1 100644 --- a/doc/manual/nix-prefetch-url.xml +++ b/doc/manual/nix-prefetch-url.xml @@ -1,54 +1,69 @@ - - nix-prefetch-url - copy a file from a URL into the store and print its MD5 hash - + + + nix-prefetch-url + copy a file from a URL into the store and print its MD5 hash + - - - nix-prefetch-url - url - - + + + nix-prefetch-url + url + hash + + - - Description - - The command nix-prefetch-url downloads the - file referenced by the URL url, - prints its MD5 cryptographic hash code, and copies it into the - Nix store. The file name in the store is - hash-basename, - where basename is everything - following the final slash in url. - +Description - - This command is just a convenience to Nix expression writers. - Often a Nix expressions fetch some source distribution from the - network using the fetchurl expression - contained in nixpkgs. However, - fetchurl requires an MD5 hash. If you don't - know the hash, you would have to download the file first, and - then fetchurl would download it again when - you build your Nix expression. Since - fetchurl uses the same name for the - downloaded file as nix-prefetch-url, the - redundant download can be avoided. - +The command nix-prefetch-url downloads the +file referenced by the URL url, prints its +cryptographic hash, and copies it into the Nix store. The file name +in the store is +hash-baseName, +where baseName is everything following the +final slash in url. - +This command is just a convenience for Nix expression writers. +Often a Nix expression fetches some source distribution from the +network using the fetchurl expression contained in +Nixpkgs. However, fetchurl requires a +cryptographic hash. If you don't know the hash, you would have to +download the file first, and then fetchurl would +download it again when you build your Nix expression. Since +fetchurl uses the same name for the downloaded file +as nix-prefetch-url, the redundant download can be +avoided. - - Examples +The environment variable NIX_HASH_ALGO specifies +which hash algorithm to use. It can be either md5, +sha1, or sha256. The default is +md5. - +If hash is specified, then a download +is not performed if the Nix store already contains a file with the +same hash and base name. Otherwise, the file is downloaded, and an +error if signaled if the actual hash of the file does not match the +specified hash. + +This command prints the hash on standard output. Additionally, +if the environment variable PRINT_PATH is set, the path +of the downloaded file in the Nix store is also printed. + + + + +Examples + + $ nix-prefetch-url ftp://ftp.nluug.nl/pub/gnu/make/make-3.80.tar.bz2 -... -file has hash 0bbd1df101bc0294d440471e50feca71 -... +0bbd1df101bc0294d440471e50feca71 + +$ PRINT_PATH=1 nix-prefetch-url ftp://ftp.nluug.nl/pub/gnu/make/make-3.80.tar.bz2 +0bbd1df101bc0294d440471e50feca71 +/nix/store/wvyz8ifdn7wyz1p3pqyn0ra45ka2l492-make-3.80.tar.bz2 + + - diff --git a/doc/manual/nix-store.xml b/doc/manual/nix-store.xml index c67e20266..0fec253bd 100644 --- a/doc/manual/nix-store.xml +++ b/doc/manual/nix-store.xml @@ -189,7 +189,7 @@ linkend="sec-nix-build">nix-build does. nix-store - + @@ -451,7 +451,7 @@ most one query can be specified. The default query is nix-store - + @@ -473,7 +473,7 @@ most one query can be specified. The default query is nix-store - + srcpath subpath @@ -501,7 +501,8 @@ deployment. Synopsis nix-store - + + @@ -514,6 +515,25 @@ automatically repaired. Inconsistencies are generally the result of the Nix store or database being modified by non-Nix tools, or of bugs in Nix itself. +There is one option: + + + + + + Checks that the contents of every valid store path + has not been altered by computing a SHA-256 hash of the contents + and comparing it with the hash stored in the Nix database at build + time. Paths that have been modified are printed out. For large + stores, is obviously quite + slow. + + + + + + +