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PACKAGE(5) File Formats Manual PACKAGE(5)

packageformat for OpenBSD binary packages

Binary packages for OpenBSD can be created using pkg_create(1) and are usually manipulated using pkg_add(1), pkg_mklocatedb(1), or pkg_info(1).

The basic underlying format is an archive following the ustar specification that can be handled with tar(1) and compressed using gzip(1).

Package names always end in “.tgz”; the file name itself should conform to packages-specs(7).

Note that the base distribution tarballs of OpenBSD (e.g. baseXXX.tgz, compXXX.tgz, ...) are not binary packages fit for pkg_add(1).

All types of archive contents can be present in a package, including files, directories, hardlinks, symlinks, fifos, block and character devices.

In order to allow just-in-time extraction, packages always begin with a table of contents, named +CONTENTS. This table of contents can be read using the API described in OpenBSD::PackingList(3p).

All the remaining information in the archive should be referenced in the packing-list, including all relevant information: symlinks destinations, special permissions, and file owners. See pkg_create(1) for annotation details.

This table of contents is always followed by a few special files, some of which are optional: the package description (+DESC), a display message (+DISPLAY), etc.

The ustar format has some limitations with respect to file names. Accordingly, the package tools will replace very long names with LongName#n and long link names with LongLink#n. The packing-list will hold the real file names, and the package tools will reconstitute the correct names behind the scenes.

All information within a package is checksummed, using SHA256 since OpenBSD 4.4. During creation and installation, meta-information, such as file owners and permissions, are also checked: any important stuff that isn't recorded in the packing-list is an error.

Packing-lists can be signed. If a signature is found, then it will be checked during installation, and failure to verify will prevent the package from installing correctly. Currently, only X.509-style signatures are supported. They rely on a certificate authority file being present as /etc/ssl/pkgca.pem and all signatures will be checked against it. Once the packing-list signature is checked, all individual packing elements will be checksummed, resulting in a ‘just-in-time’ signature checking.

Fat packages were removed in OpenBSD 5.1, since no practical application was found.

pkg_add(1), pkg_create(1), pkg_info(1), packages(7), packages-specs(7)

Packages are valid gzip'ed ustar archives that can be extracted using tar(1). In particular, hardlink names should be valid, and all items will extract to different names. However, it may be a bit difficult to make sense of the package contents without peeking at the packing-list.

September 29, 2011 OpenBSD-5.4