docker: Fix $DOCKER_USER

Now we cp instead of mv $HOME as mv will fail due to the
user not existing.

We also only try to convert if the user hasn't been changed.

Finally I added usage to the docker docs in install.md

Closes #2056

Author: nhooyr

ci/release-image/entrypoint.sh

@@ -1,16 +1,20 @@
-#!/usr/bin/env sh
+#!/bin/sh
 set -eu
 
 if [ "${DOCKER_USER-}" ]; then
   echo "$DOCKER_USER ALL=(ALL) NOPASSWD:ALL" | sudo tee -a /etc/sudoers.d/nopasswd > /dev/null
   sudo usermod --login "$DOCKER_USER" \
-    --move-home --home "/home/$DOCKER_USER" \
+    --home "/home/$DOCKER_USER" \
     coder
   sudo groupmod -n "$DOCKER_USER" coder
 
+  # We cannot use usermod to do this as it uses mv which will
+  # fail as files are open in $HOME. We have to copy.
+  sudo cp -a "$HOME" "/home/$DOCKER_USER"
+  export HOME="/home/$DOCKER_USER"
+
   sudo sed -i "/coder/d" /etc/sudoers.d/nopasswd
   sudo sed -i "s/coder/$DOCKER_USER/g" /etc/fixuid/config.yml
-  export HOME="/home/$DOCKER_USER"
 fi
 
 # This isn't set by default.

doc/install.md

@@ -179,10 +179,11 @@ code-server
 # easily access/modify your code-server config in $HOME/.config/code-server/config.json
 # outside the container.
 mkdir -p ~/.config
-docker run -it -p 127.0.0.1:8080:8080 \
+docker run -it --name code-server -p 127.0.0.1:8080:8080 \
   -v "$HOME/.config:/home/coder/.config" \
   -v "$PWD:/home/coder/project" \
   -u "$(id -u):$(id -g)" \
+  -e "DOCKER_USER=$USER" \
   codercom/code-server:latest
 ```