WSL - Windows SubSytem For Linux

Editor's Notes

• #3: WSL is mainly for development scenarios. NOT for production scenarios.Major adv is Windows <-> Linux interop
• #4: 1. WSL2 requires windows insider build 18917 or higher.2. You can install multiple linux distros (only one will be default).2. Can be installed in one of the following ways:Download & install from Microsoft store.Download & install APPX.2. Installation on Win Server has additional steps (unzip appx file & run installer).
• #7: 7. Run “ls -l /usr/bin/wsl*“ to see list of wsl utilitieswslsyswslfetch –splash (takes a bit of time)wslvar –getsys8. Run “sudo /etc/init.d/docker start” to start dockerDocker psDocker imagesDocker run –it alpine /bin/sh
• #8: 1. WSL2 requires windows insider build 18917 or higher.2. You can install multiple linux distros (only one will be default).2. Can be installed in one of the following ways:Download & install from Microsoft store.Download & install APPX.2. Installation on Win Server has additional steps (unzip appx file & run installer).
• #10: @todo: Show examples with “--set-version” and “--unregister”.
• #11: 1. The \\WSL$ is facilitated by 9P server (running inside /init)
• #17: 5.1. To clarify:- If linux command prompt is under /mnt/xyz, then the windows command gets the same as its current directory.- If linux command prompt is elsewhere, then the windows command gets %WINDIR% as its current directory.
• #20: - /etc/fstab is processed on WSL start. /etc/fstab is a file where you can declare other filesystems, like an SMB share. Thus, you can mount these filesystems automatically in WSL on start up.- /etc/hosts file, contains hostname <-> ip mapping- /etc/resolv.conf file, contains list of DNS resolution servers
• #21: 1.2. Not really a limitation. More like a blessing.3.1. We’ll explore more in detail in WSL2 architecture.
• #22: @todo: wslpath
• #24: NTDLL, PEB, TEB etc are the standard interfaces between user-mode processes and the NT kernel. 3. Pico processes do not interact with NT Kernel directly.3. When NT Kernel detect a process without PEB/TEB/NTDLL, it asks LXSS/LXCore to interact with it instead. 3. @todo: The pico providers (LXSS/LXCore) provide POSIX compliance for NT Kernel?
• #27: 1. VFS abstracts all file system operations. 1. Various ile systems are mounted on different directories in the VFS namespace. 1. VFS utilizes a number of data structures- inodes - directory entries - file objects- file descriptors,- special files (device files, FIFOs, sockets, symbolic links).
• #28: 2. The first time an NT process requests launching a Linux binary an instance is created. Once the last NT client closes, the Linux instance is terminated. Notes on /init: /init is a multi-purpose binary that was written by Microsoft and is shipped as a binary resource contained in LxssManager.dll. When /init is launched, it first checks its PID. If the PID is 1, /init will run in "daemon mode" where it essentially the Lxss Manger service’s endpoint inside a WSL instance. If the PID is not 1, /init runs as "binfmt_misc interpreter mode" which allows launching NT binaries.
• #29: Advantages of WSL2 over WSL- Faster file access- Full kernel implementation7. Key thing to remember is that linux is running side-by-side with windows (and not inside it).
• #30: 4. The EXT4 VHD is mapped in. Then the /init process is run.
• #31: Important to note that:In WSL1, both Windows & Linux were running on same machine.In WSL2, they are running in “separate” machines.The P9 server facilitates Windows <-> Linux file sharing.- In the scenario above, P9 allows Linux VM access to windows file share
• #32: 9P facilitates \\WSL$ share
• #33: P9 here facilitates mounting of windows file share
• #34: Single linux kernel serves multiple distros