BitBake provides support to download files this procedure is called fetching and it handled by the fetch and fetch2 modules. At this point the original fetch code is considered to be replaced by fetch2 and this manual only related to the fetch2 codebase. The SRC_URI is normally used to tell BitBake which files to fetch. The next sections will describe the available fetchers and their options. Each fetcher honors a set of variables and per URI parameters separated by a ; consisting of a key and a value. The semantics of the variables and parameters are defined by the fetcher. BitBake tries to have consistent semantics between the different fetchers. The overall fetch process is that first, fetches are attempted from PREMIRRORS. If those don't work, the original SRC_URI is attempted and if that fails, BitBake will fall back to MIRRORS. Cross urls are supported, so its possible to mirror a git repository on an http server as a tarball for example. Some example commonly used mirror definitions are: PREMIRRORS ?= "\ bzr://.*/.* http://somemirror.org/sources/ \n \ cvs://.*/.* http://somemirror.org/sources/ \n \ git://.*/.* http://somemirror.org/sources/ \n \ hg://.*/.* http://somemirror.org/sources/ \n \ osc://.*/.* http://somemirror.org/sources/ \n \ p4://.*/.* http://somemirror.org/sources/ \n \ svk://.*/.* http://somemirror.org/sources/ \n \ svn://.*/.* http://somemirror.org/sources/ \n" MIRRORS =+ "\ ftp://.*/.* http://somemirror.org/sources/ \n \ http://.*/.* http://somemirror.org/sources/ \n \ https://.*/.* http://somemirror.org/sources/ \n" Non-local downloaded output is placed into the directory specified by the DL_DIR. For non local archive downloads the code can verify sha256 and md5 checksums for the download to ensure the file has been downloaded correctly. These may be specified either in the form SRC_URI[md5sum] for the md5 checksum and SRC_URI[sha256sum] for the sha256 checksum or as parameters on the SRC_URI such as SRC_URI="http://example.com/foobar.tar.bz2;md5sum=4a8e0f237e961fd7785d19d07fdb994d". If BB_STRICT_CHECKSUM is set, any download without a checksum will trigger an error message. In cases where multiple files are listed in SRC_URI, the name parameter is used assign names to the urls and these are then specified in the checksums in the form SRC_URI[name.sha256sum].

The URN for the local file fetcher is file. The filename can be either absolute or relative. If the filename is relative, FILESPATH and failing that FILESDIR will be used to find the appropriate relative file. The metadata usually extend these variables to include variations of the values in OVERRIDES. Single files and complete directories can be specified. SRC_URI = "file://relativefile.patch" SRC_URI = "file://relativefile.patch;this=ignored" SRC_URI = "file:///Users/ich/very_important_software"

The URN for the CVS fetcher is cvs. This fetcher honors the variables CVSDIR, SRCDATE, FETCHCOMMAND_cvs, UPDATECOMMAND_cvs. DL_DIR specifies where a temporary checkout is saved. SRCDATE specifies which date to use when doing the fetching (the special value of "now" will cause the checkout to be updated on every build). FETCHCOMMAND and UPDATECOMMAND specify which executables to use for the CVS checkout or update. The supported parameters are module, tag, date, method, localdir, rsh and scmdata. The module specifies which module to check out, the tag describes which CVS TAG should be used for the checkout. By default the TAG is empty. A date can be specified to override the SRCDATE of the configuration to checkout a specific date. The special value of "now" will cause the checkout to be updated on every build. method is by default pserver. If ext is used the rsh parameter will be evaluated and CVS_RSH will be set. Finally, localdir is used to checkout into a special directory relative to CVSDIR. SRC_URI = "cvs://CVSROOT;module=mymodule;tag=some-version;method=ext" SRC_URI = "cvs://CVSROOT;module=mymodule;date=20060126;localdir=usethat"

The URNs for the HTTP/FTP fetcher are http, https and ftp. This fetcher honors the variables FETCHCOMMAND_wget. FETCHCOMMAND contains the command used for fetching. ${URI} and ${FILES} will be replaced by the URI and basename of the file to be fetched. SRC_URI = "http://oe.handhelds.org/not_there.aac" SRC_URI = "ftp://oe.handhelds.org/not_there_as_well.aac" SRC_URI = "ftp://you@oe.handheld.sorg/home/you/secret.plan"

The URN for the SVN fetcher is svn. This fetcher honors the variables FETCHCOMMAND_svn, SVNDIR, SRCREV. FETCHCOMMAND contains the subversion command. SRCREV specifies which revision to use when doing the fetching. The supported parameters are proto, rev and scmdata. proto is the Subversion protocol, rev is the Subversion revision. If scmdata is set to keep, the .svn directories will be available during compile-time. SRC_URI = "svn://svn.oe.handhelds.org/svn;module=vip;proto=http;rev=667" SRC_URI = "svn://svn.oe.handhelds.org/svn/;module=opie;proto=svn+ssh;date=20060126"

The URN for the GIT Fetcher is git. The variable GITDIR will be used as the base directory where the git tree is cloned to. The parameters are tag, protocol and scmdata. tag is a Git tag, the default is master. protocol is the Git protocol to use and defaults to git if a hostname is set, otherwise its file. If scmdata is set to keep, the .git directory will be available during compile-time. SRC_URI = "git://git.oe.handhelds.org/git/vip.git;tag=version-1" SRC_URI = "git://git.oe.handhelds.org/git/vip.git;protocol=http"