linux: added 7z and moved arch-linux into linux folder

wiki/linux/7-zip.md

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+# 7-zip
+
+[7-zip](https://7-zip.org/) is a free and open-source file archiver.
+It places files or directories in an archive and is able to compress them.
+
+## Setup
+
+7-zip can be installed by installing the packages `p7zip-full` and `p7zip-rar` on Ubuntu systems.
+On [Arch Linux](/wiki/linux/arch-linux.md) it can be installed with the package `7-zip`
+from the [AUR](/wiki/linux/package_manager.md#arch-linux-pacman-and-yay).
+
+## Usage
+
+### Compressing and Uncompressing a Directory
+
+For directories to be compressed the Lempel–Ziv–Markov chain algorithm is recommended.
+It is fast with good compression results.
+
+As explained by
+[kenorb on superuser.com](https://superuser.com/questions/281573/what-are-the-best-options-to-use-when-compressing-files-using-7-zip)
+An effective way to compress a directory is the following command where `directory` is the directory
+that is to be compressed.
+The archive will be created by the same name as the directory but with the `.7z` extension.
+This command uses [expansion](/wiki/linux/shell.md#expansion).
+The directory is not deleted automatically afterwards.
+
+```sh
+7z a -t7z -m0=lzma -mx=9 -mfb=64 -md=32m -ms=on directory{.7z,}
+```
+
+To uncompress it run the following command.
+
+```sh
+7z x directory.7z
+```
+
+### Peek Contents of an Archive
+
+To list the content files of a 7-zip archive the following command can be used.
+The name of the archive is assumed to be `directory.7z`.
+
+```sh
+7z l directory.7z
+```