211 lines
6.5 KiB
Markdown
211 lines
6.5 KiB
Markdown
+++
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title = "Running Emacs with wsl2-xrdp"
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[taxonomies]
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tags = [ "wsl", "emacs" ]
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categories = ["os", "apps" ]
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+++
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# Why
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I have been using Emacs in WSL2 using an X server running in Windows and
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that works fine as long as long as the computer does not go to sleep.
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When the computer goes to sleep, the X connection is cut and the emacs
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process crashes. I like to just have my emacs session available so I can
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continue where I was last time and I like my computer to go to sleep
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when I not use it because Global Warming.
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- start emacs in WSL2 in GUI mode
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- can be reconnected after sleep
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- copy-paste works transparent
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# Plan
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- use **xrdp** as remote desktop is built into windows
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- configure xrdp to startup in WSL2
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- run emacs in a remote desktop session
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# Installation
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## Install xrdp
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[Arch wiki page for xrdp](https://wiki.archlinux.org/index.php/xrdp)
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``` shell
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$ yay -S xrdp xorgxrdp-git
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```
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We do not have systemd in WSL2 so I started the daemons manually with a
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small script \*/usr/local/bin/start-xrdp:
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``` shell
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#!/bin/bash
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sudo /usr/sbin/xrdp
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sudo /usr/sbin/xrdp-sesman
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```
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We can now start it with **start-xrdp** from the bash command line or
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using **wsl -u root /usr/local/bin/start-xrdp**. If not running as root
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(or recently authenticated sudo access) it will ask for your Linux
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password to allow running as **sudo**.
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Trying to connect lets me login but after a timeout is shows a dialog
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box telling me Xorg did not want to start. This is confirmed in the
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**/var/log/xrdp-sesman.log** file.
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The root cause is that I cannot read properly because if I could, I
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would have read to add *allowed\\~users~=anybody* to the
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**/etc/X11/Xwrapper.config** file to allow **Xorg** to be started by
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regular users like me instead of only **root**.
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Once that is there I get a nice black screen after login.
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Note: Each time WSL2 restarts it gets a random ip address. So I created
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a small script to dig out the actual ip address out of the output of
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**ip address** :
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``` shell
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#!/bin/bash
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ip address show dev eth0 | grep "inet " | sed -e 's/.*inet \([^/]*\).*/\1/'
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```
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Which I gave the original name of **/usr/local/bin/ip-address** (do not
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forget to `chmod +x /usr/local/bin/ip-address` to make it executable) so
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I can easily call it from powershell with `wsl ip-address`.
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## Installing DBUS replacement
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DBUS is the de-facto GNU/Linux desktop communication bus which glues all
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kind of GUI apps together. I do not know if it is directly used by Emacs
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or any of the extensions I use, however it reduces the amount of errors
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and warnings.
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``` shell
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$ yay -S dbus-x11
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```
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allows xfce and other programs to feel happy and display the desktop
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with an emacs window. Now just maximizing the window and the goal is
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reached.
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## Automatic start of Emacs only
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In order to just start emacs maximized in a single remote desktop window
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we only need to start it as the only program in the XSession. This of
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course also means there is no chrome on the X-Window or the ability to
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lauch other programs outside of Emacs. This is exactly how I like it.
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``` shell
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#file:~/.xinitrc
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emacs -mm
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```
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If you rather have a full desktop environment, see further.
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## Installing Xfce4 (Optional)
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I\'d rather have something more lightweight as window manager, but I
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have experience with Xfce4 in Arch and I also like something which just
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works.
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I only intend to run emacs in the window however having something a bit
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more capable which works can help me debug the environment. (I have some
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font things to sort out too...)
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``` shell
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$ sudo pacman -S xfce4
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```
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and then start it form **\~/.xinitrc**
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``` shell
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emacs &
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startxfce4
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```
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If you have skipped the **DBUS** setup above, this hangs while the
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**\~/.xorgxrdp.log** file is filling up with errors complaining about
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missing connection to dbus.
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# Using this from Windows
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## Starting from the command-line
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We can start remote desktop session using
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>_ mstsc /v:$(wsl ip-address) /h:2560 /w:1600
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This works, however we get now a prompt to accept the certificate and we
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still need to login. We can make this smoother
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## Accepting the certificate
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You can accept the certificate and let remote desktop add it to your
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certificate stores. This solves this interruption.
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However, this still happens each time the ip address changes.
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## Automatic login
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Start **remote desktop** GUI using the search or from the start menu.
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Fill in the ip address returned by `wsl ip-address` and your username.
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Enable the flag to store your password. Login and save the configuration
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as e.g. **emacs.rdp**.
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We can now start emacs using
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>_ cmdkey /generic:$(wsl ip-address) /user:<username> /pass:<password>
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>_ mstsc /v:$(wsl ip-address)
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We can assemble this is a small script **wsl-emacs.ps1** somewhere on
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your path:
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``` powershell
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wsl -u root /usr/local/bin/start-xrdp
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$address = $(wsl ip-address)
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$userName = "pti"
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$userPwd = "shht!Secret"
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cmdkey /generic:$address /user:$userName /pass:$userPwd
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mstsc /v:$address
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```
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Which allows us to start our **wsl-emacs** from powershell or as a
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startup application with a shortcut. It ensures the **xrdp** daemons are
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running (they are idempotent, so the script can be run multiple times),
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then the credentials are created so they can be picked up by remote
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desktop.
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To add a shortcut to the start menu:
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- Type Win-R and open
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\*%AppData%`\Microsoft`{=latex}`\Windows`{=latex}`\Start`{=latex}
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Menu`\Programs*`{=latex}
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- create a new shortcut
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- set as target \*powershell.exe \"&
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\'\<path-of-script\>`\wsl`{=latex}-emacs.ps1\'
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Note the weird **\"&** on the command-line.
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## A note on security
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Since you can run any command from the windows command-line as root, the
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current logged in person has full access to anything in the WSL Linux
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machines. As such there is not a big hole added by adding your linux
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password somewhere securely in your account files such as the startup
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script.
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This does not mean you should not have secure passwords, as your linux
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box can expose its ports (not by default but just assume they are) and
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allow e.g. ssh access. Since I assume a lot of WSL2 hosts will be used
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fast and loose as a development box, there is a good chance that sooner
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or later a port is opened for reasons.
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So I would not worry too much your linux box password is exposed in the
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emacs startup script as long as it is hard enough and not used anywhere
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else. If you\'d like to get it from some secure vault on your PC or from
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your infrastructure, go for it.
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tldr;
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- use a strong password for your WSL box
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- do not reuse an existing password
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- secure your startup script so it is only readable by you.
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