fix: Clean up entrypoint.sh and fix potential issues (#1613)

Backported-from: main
Backported-to: 23.03

Author: achimnol

changes/1613.fix.md

@@ -0,0 +1 @@
+Clean up `entrypoint.sh` (our custom container entrypoint), including fixes to avoid non-mandatory recursive file operations on `/home/work`

src/ai/backend/runner/entrypoint.sh

@@ -12,12 +12,16 @@ if [ -z "$LOCAL_USER_ID" ]; then
   echo "WARNING: \$LOCAL_USER_ID is an empty value. This may be a misbehavior of plugins manipulating the evironment variables of new containers and cause unexpected errors."
 fi
 
+# NOTE: /home/work may have vfolder bind-mounts containing a LOT of files (e.g., more than 10K!).
+#       Therefore, we must AVOID any filesystem operation applied RECURSIVELY to /home/work,
+#       to prevent indefinite "hangs" during a container startup.
+
 if [ $USER_ID -eq 0 ]; then
 
   echo "WARNING: Running the user codes as root is not recommended."
   if [ -f /bin/ash ]; then  # for alpine
     export SHELL=/bin/ash
-  else
+  else  # for other distros (ubuntu, centos, etc.)
     export SHELL=/bin/bash
     echo "$LD_PRELOAD" | tr ':' '\n' > /etc/ld.so.preload
     unset LD_PRELOAD
@@ -68,7 +72,7 @@ else
       usermod -aG shadow $USER_NAME
     fi
     export SHELL=/bin/ash
-  else
+  else  # for other distros (ubuntu, centos, etc.)
     echo "$LD_PRELOAD" | tr ':' '\n' > /etc/ld.so.preload
     unset LD_PRELOAD
     if [ -z "$GROUP_NAME" ]; then
@@ -80,11 +84,16 @@ else
       useradd -s /bin/bash -d "/home/$USER_NAME" -M -r -u $USER_ID -g $GROUP_NAME -o -c "User" $USER_NAME
       usermod -aG shadow $USER_NAME
     else
-      cp -R "/home/$USER_NAME/*" /home/work/
-      cp -R "/home/$USER_NAME/.*" /home/work/
+      # The image has an existing user name for the given uid.
+      # Merge the image's existing home directory into the bind-mounted "/home/work" from the scratch space.
+      # NOTE: Since the image layer and the scratch directory may reside in different filesystems,
+      #       we cannot use hard-links to reduce the copy overhead.
+      #       It assumes that the number/size of files in the image's home directory is not very large.
+      cp -Rp "/home/$USER_NAME/*" /home/work/
+      cp -Rp "/home/$USER_NAME/.*" /home/work/
+      # Rename the user to "work" and let it use "/home/work" as the new home directory.
       usermod -s /bin/bash -d /home/work -l work -g $GROUP_NAME $USER_NAME
       USER_NAME=work
-      chown -R $USER_NAME:$GROUP_NAME /home/work
       usermod -aG shadow $USER_NAME
     fi
     export SHELL=/bin/bash