pxar Command-line Tool

pxar is a command-line utility for creating and manipulating archives in the Proxmox File Archive Format (.pxar). It is inspired by casync file archive format, which caters to a similar use-case. The .pxar format is adapted to fulfill the specific needs of the Proxmox Backup Server, for example, efficient storage of hard links. The format is designed to reduce the required storage on the server by achieving a high level of deduplication.

Creating an Archive

Run the following command to create an archive of a folder named source:

# pxar create archive.pxar /path/to/source

This will create a new archive called archive.pxar with the contents of the source folder.

Note

pxar will not overwrite any existing archives. If an archive with the same name is already present in the target folder, the creation will fail.

By default, pxar will skip certain mount points and will not follow device boundaries. This design decision is based on the primary use case of creating archives for backups. It makes sense to ignore the contents of certain temporary or system specific files in a backup. To alter this behavior and follow device boundaries, use the --all-file-systems flag.

It is possible to exclude certain files and/or folders from the archive by passing the --exclude parameter with gitignore-style match patterns.

For example, you can exclude all files ending in .txt from the archive by running:

# pxar create archive.pxar /path/to/source --exclude '**/*.txt'

Be aware that the shell itself will try to expand glob patterns before invoking pxar. In order to avoid this, all globs have to be quoted correctly.

It is possible to pass the --exclude parameter multiple times, in order to match more than one pattern. This allows you to use more complex file inclusion/exclusion behavior. However, it is recommended to use .pxarexclude files instead for such cases.

For example you might want to exclude all .txt files except a specific one from the archive. This would be achieved via the negated match pattern, prefixed by !. All the glob patterns are relative to the source directory.

# pxar create archive.pxar /path/to/source --exclude '**/*.txt' --exclude '!/folder/file.txt'

Note

The order of the glob match patterns matters, as later ones override earlier ones. Permutations of the same patterns lead to different results.

pxar will store the list of glob match patterns passed as parameters via the command line, in a file called .pxarexclude-cli, at the root of the archive. If a file with this name is already present in the source folder during archive creation, this file is not included in the archive, and the file containing the new patterns is added to the archive instead. The original file is not altered.

A more convenient and persistent way to exclude files from the archive is by placing the glob match patterns in .pxarexclude files. It is possible to create and place these files in any directory of the filesystem tree. These files must contain one pattern per line, and later patterns override earlier ones. The patterns control file exclusions of files present within the given directory or further below it in the tree. The behavior is the same as described in Creating Backups.

Extracting an Archive

An existing archive, archive.pxar, is extracted to a target directory with the following command:

# pxar extract archive.pxar /path/to/target

If no target is provided, the contents of the archive is extracted to the current working directory.

In order to restore only parts of an archive, single files, and/or folders, it is possible to pass the corresponding glob match patterns as additional parameters or to use the patterns stored in a file:

# pxar extract etc.pxar /restore/target/etc --pattern '**/*.conf'

The above example restores all .conf files encountered in any of the sub-folders in the archive etc.pxar to the target /restore/target/etc. A path to the file containing match patterns can be specified using the --files-from parameter.

List the Contents of an Archive

To display the files and directories contained in an archive archive.pxar, run the following command:

# pxar list archive.pxar

This displays the full path of each file or directory with respect to the archive's root.

Mounting an Archive

pxar allows you to mount and inspect the contents of an archive via FUSE. In order to mount an archive named archive.pxar to the mount point /mnt, run the command:

# pxar mount archive.pxar /mnt

Once the archive is mounted, you can access its content under the given mount point.

# cd /mnt
# ls
bin   dev  home  lib32  libx32      media  opt   root  sbin  sys  usr
boot  etc  lib   lib64  lost+found  mnt    proc  run   srv   tmp  var