SLP format archives consist of two separate segments: a compressed archive of variable size and a fixed-length data structure containing package control data (the SLP header).
The compressed archive represents the beginning of the SLP format file. GNU tar (Tape ARchiver) is used for archive generation. The tar archive is compressed using bzip2 compression, with default blocking factor. Standard 'tar' and 'bzip2' tools may be used to extract package file contents; data following the compressed archive in the SLP format file will be ignored.
Archive contents for SLP format files are governed by distribution-specific policies and are generally outside the scope of this specification. Each distribution is responsible for maintaining its own (or selecting its own) SLP packaging guidelines, which shall dictate file layout on the filesystem, stripping of files, compression of documentation and other factors related to packaged data.
The SLP header is appended to the tail (end) of a compressed archive. This header is a fixed-length, fixed-format data structure containing 3785 bytes of data. This fixed-format data structure contains 19 fixed-length fields.
It is possible to create a file which contains only a SLP header and does not contain a compressed file. These files will be known as detached SLP header files. Detached SLP header files may be created for sample purposes, or as a potential template to be attached to the end of compressed archives as needed.