|PACKAGE(5)||File Formats Manual||PACKAGE(5)|
package — format
for OpenBSD binary packages
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. baseXX.tgz, compXX.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 (pkg_create(1) and pkg_add(1) actually enforce this). 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 basic ustar format has some limitations with respect to file names. Packages now use the "extended record specification" (header type x) for long links and long file names. Other extended ustar headers are currently recognized, but not supported.
Starting with OpenBSD 5.5, the compressed archive may be composed of several gzip(1) archives concatenated together. gzip(1) doesn't mind, and tar(1) is happy as long as the uncompressed stream is sane. This allows for faster signing and better rsync properties.
Starting with OpenBSD 5.6, tarballs are stored "out-of-order": each archive entry will match an entry in the packing-list (and all file-like entries will be matched), but the order will be adjusted so that most recently changed files come first, in order to allow faster updates.
User annotations are described in pkg_create(1). The following annotations are automatically inserted during package creation and installation:
-Aarches of pkg_create(1)
@comment pkgpath=path ftp=yes/no
-DFTP arguments to pkg_create(1).
packageto record that the entry is actually a hard link.
-Voptions from pkg_create(1), and triggers updates when it changes.
Note that most of these annotations cannot be added manually, as pkg_create(1) will error out.
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.
Starting with OpenBSD 6.1,
gzip(1) header signatures are the only
supported format. This allows for ‘just-in-time’ signature
checking, as the binary data is checked in 64K bytes long chunks.
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.
|December 4, 2019||OpenBSD-current|