A MatterLinux package is a compiled files of a software, tool or a libary. 

# Format 
MatterLinux packages uses the **M**atterLinux **P**ackaging **F**ormat, `MPF`. Don't let fancy name 
mislead you, a basic `MPF` file is just a renamed `TAR GZ` archive. The reason that packages use the 
`.mpf` extension and not the `.tar.gz` extension is to make it easier to recognize and easier to work 
with in the scripts and the tools. 

### Naming
A package is named after the software and the version of that software that it provides. For 
example package containing `bash` version `5.2.15` is named `bash_5.2.15.mpf`.

### Structure 
File structure of a package matches with the MatterLinux root file structure. This is important
as a package will most likely be extracted in a MatterLinux root filesystem. 

For example, we can take a look at the `which` package, to do this you can download the `MPF` file 
and list its contents with the `tar tf` command:
```
usr/
usr/share/
usr/share/man/
usr/share/man/man1/
usr/share/man/man1/which.1
usr/share/info/
usr/share/info/dir
usr/share/info/which.info
usr/bin/
usr/bin/which
```

### Install Scripts
Some packages may contain an install script, `install.sh`, this shell script is ran by the 
[MatterLinux Package Manager (`mp`)](/wiki/package_man) using the bash shell, right after the 
extraction.

This script is used to do post-install actions, such as adding users, groups etc.

This script is located at the root of the package. For example let's take a look 
at the `systemd` package:
```
...
etc/X11/xinit/
etc/X11/xinit/xinitrc.d/
etc/X11/xinit/xinitrc.d/50-systemd-user.sh
etc/credstore.encrypted/
install.sh
usr/
usr/lib/
usr/lib/libudev.so
usr/lib/libnss_resolve.so.2
...
```

# Usage
While installing a package using the [MatterLinux Package Manager (`mp`)](/wiki/package_man), `mp` 
downloads the target package(s) from the repos, these packages are in the format discussed above.
After downloading and verifying the target package(s), `mp` extracts the packages [using the `tar`
tool](https://git.matterlinux.xyz/Matterlinux/mp/src/main/src/utils/util.c#L103). 

To learn more about this process see the [page for `mp`](/wiki/package_man).

It's also possible to install packages manualy. To do this you can grab a package you want 
and extract it to your the root directory by running: `tar xvf <package_version.mpf> -C /`

# Building  
Package are built with the `mp-repo` tool. In order to build a package, you will need the source 
for the repo that contains the package. This is because a package itself does not store any metadata, 
this is all handled by the repo. 

To learn more about the `mp-repo` tool, and how you can use it to build packages, see the 
[repo package](/wiki/repo).

### Package Source
Source code for a packages can be found in the source code of the repo that the package is in.
Source files for a repo will be located under the `src` directory.

### Package Script 
Each package source contains a `pkg.sh` shell script. This is the source script that is used to 
build the package. In the build process, this shell script gets imported  by the `mp-repo` tool 
using the `source` command.

Let's take a closer look at a `pkg.sh` file:
```
NAME="which"
DESC="Shows the full path of (shell) commands"
VERSION="2.21"
FILES=("https://ftp.gnu.org/gnu/which/which-$VERSION.tar.gz")
HASHES=("097ff1a324ae02e0a3b0369f07a7544a")
DEPENDS=()

build() {
  tar xf $NAME-$VERSION.tar.gz
  cd $NAME-$VERSION

  ./configure --prefix=/usr && make
  make DESTDIR=$ROOTDIR install

  cd .. && rm -rf $NAME-$VERSION 
}
```
This `pkg.sh` file is for the `which` package (version `2.21`). Let's start by breaking down the 
variables:

- `NAME`: Specifies the package name. A package should be named after the software, tool or libary 
it provides. Preferably the name should not contain `_` to avoid confusion with naming. 
- `DESC`: A short description about the software, tool or the libary that package provides. 
Explain what it does, what it contains etc.
- `VERSION`: Version of the software, tool or libary the package provides. If you are using a 
git commit version, you can name the version `LAST_VERSION+COMMIT_ID`
- `FILES`: Upstream files and patches needed to build this package, you can use `http`, `https` 
or `ftp` protocols.
You can also specify multiple files. These files will be downloaded by `mp-repo` in the build 
process.
- `HASHES`: Hashes for the files you specify. You can use `MD5`, `SHA1`, `SHA256` or `SHA512` sums.
And yes, you need to specify hashes for all the files, using the same order with the `FILES` variable.
- `DEPENDS`: Package(s) that this package depends on. 

Now let's take a look at the `build` function. Each package needs a `build` function, this 
function is called by `mp-repo` after downloading and verifying all the packages. It will be 
called in the `$ROOTDIR`. This directory will contain all the downloaded files, any files 
in this directory will be included into the build, so don't forget to cleanup. 

**Note:** You don't need to cleanup the downloaded files, they will be cleaned by the `mp-repo`.

- `tar xf $NAME-$VERSION.tar.gz`: Extract the downloaded archive file.
- `cd $NAME-$VERSION`: Change directory into the extracted directory.
- `./configure --prefix=/usr && make`: Builds the `which` tool, different packages may have 
different build instructions. These instruction are usually provided by the upstream. You can 
also check out [LFS](https://www.linuxfromscratch.org/lfs/view/12.0-systemd/) and [BLFS](https://www.linuxfromscratch.org/blfs/view/12.0-systemd/) for instructions.
- `make DESTDIR=$ROOTDIR install`: Install the package. Make sure that you are installing the package 
into the `$ROOTDIR` and not the root file system.
- `cd .. && rm -rf $NAME-$VERSION`: Change directory back into `$ROOTDIR` and clean the extracted archive.

Check out [`base`](https://git.matterlinux.xyz/Matterlinux/base) and 
[`desktop`](https://git.matterlinux.xyz/Matterlinux/desktop) repo sources for more 
example `pkg.sh` scripts.