[readme]: add LINUX_DEPENDENCIES doc

Author: legomushroom

README.md

@@ -17,22 +17,7 @@ For instance, if you are using a `VPN` client to connect to private enterprise n
 
 2. The extension relies on `gh codespace ssh` command to establish SSH tunnel to a Codespace, hence you need to setup ssh keys if you didn't before. If you can do `sudo gh codespace ssh` (`sudo` is important since kernel might use different identity under non-root user) and connect to a Codespace successfully, - you are good to go. Refer to [Generating a new SSH key and adding it to the ssh-agent](https://docs.github.com/en/authentication/connecting-to-github-with-ssh/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent) for more info. List of known issues and workarounds for them can be found [here](https://github.com/github/gh-net/issues?q=is%3Aissue+is%3Aopen+label%3Aknown-issue).
 
-3. If your codespace uses a non-default image, ensure that both the [GitHub CLI](https://cli.github.com/) and an SSH server are installed inside the codespace. 
-
-One way to install these prereqs on a debian-based image is by adding the following to the `features` property of your `devcontainer.json` file.
-```jsonc
-// devcontainer.json
-{
-    "features": {
-        "github-cli": "latest",
-        "sshd": "latest"
-    }
-}
-```
-
-Rebuild the codespace to apply the newly added dev container features.
-
-
+3. If your codespace uses a non-default image, ensure that both the [GitHub CLI](https://cli.github.com/), `openssh-server` and `sudo` are installed inside the codespace. Some distros need an `ssh` group too. Please see [linux dependencies doc](./docs/LINUX_DEPENDENCIES.md) for per-distro instructions.
 
 ## Installation
 

docs/LINUX_DEPENDENCIES.md

@@ -0,0 +1,50 @@
+## List of Linux dependencies by distro
+
+### Ubuntu/Debian
+
+#### Automatic setup
+
+Add to `devcontainer.json`:
+
+```jsonc
+{
+    "features": {
+        "github-cli": "latest",
+        "sshd": "latest"
+    }
+}
+```
+
+#### Manual setup
+
+1. Sudo: `apt install sudo`
+
+2. GitHub CLI: see https://github.com/cli/cli/blob/trunk/docs/install_linux.md#debian-ubuntu-linux-raspberry-pi-os-apt
+
+3. Openssh server: `sudo apt install openssh-server && service ssh start`
+
+### Alpine Linux
+
+1. GitHub CLI: see https://github.com/cli/cli/blob/trunk/docs/install_linux.md#alpine-linux
+
+### Arch Linux
+
+1. Sudo: `echo "y" | pacman -S sudo`
+
+2. GitHub CLI: see https://github.com/cli/cli/blob/trunk/docs/install_linux.md#arch-linux
+
+3. SSH group: `sudo groupadd -f ssh`
+
+### CentOS
+
+1. Sudo
+
+```shell
+dnf --disablerepo '*' --enablerepo=extras swap -y centos-linux-repos centos-stream-repos
+dnf -y distro-sync
+dnf install -y sudo
+```
+
+2. GitHub CLI: see https://github.com/cli/cli/blob/trunk/docs/install_linux.md#fedora-centos-red-hat-enterprise-linux-dnf
+
+3. SSH group: `groupadd ssh`