Another Process Becomes Stuck

Oct 13, 2025 by wbrum.org 83 views

Introduction

Remote Desktop Protocol (RDP) is a popular method for accessing and controlling remote computers. However, when using RDP to connect to an ARM64 container on Ubuntu 22.04 and 24.04, users may encounter a blank screen issue. This problem is particularly frustrating, as it prevents users from accessing their remote desktop. In this article, we will explore the causes of this issue and provide a solution to fix it.

The Problem

The blank screen issue occurs when using RDP to connect to an ARM64 container on Ubuntu 22.04 and 24.04. The problem is not present when using the same container on an AMD64 (x86_64) image. This suggests that the issue is specific to the ARM64 architecture.

Investigating the Issue

To investigate the issue, we can use the ps -aux command to list the running processes while the blank screen is displayed. This will help us identify the processes that are causing the issue.

ubuntu@dd1955ce2745:~$ ps -aux

Running this command reveals that the /etc/xdg/xfce4/xinitrc script is hung. Upon further investigation, we find that the offending command is systemctl --user list-jobs.

Replicating the Error

To replicate the error, we can change to the ubuntu user account using su - ubuntu and then create a DBUS socket using eval "$(dbus-launch --sh-syntax)". This populates the DBUS_SESSION_BUS_ADDRESS variable.

ubuntu@dd1955ce2745:~$ su - ubuntu
ubuntu@dd1955ce2745:~$ eval "$(dbus-launch --sh-syntax)"
ubuntu@dd1955ce2745:~$ echo $DBUS_SESSION_BUS_ADDRESS
unix:path=/tmp/dbus-7tJaBNAH44,guid=cbc9484cdee04517f8769cce67cf90ee

Running the systemctl --user list-jobs command will stop responding and hang. This is because the DBUS_SESSION_BUS_ADDRESS variable is set, which causes the systemctl command to hang.

Fixing the Issue

To fix the issue, we can add unset DBUS_SESSION_BUS_ADDRESS at the start of the /etc/xdg/xfce4/xinitrc script. This will allow the systemctl --user commands to fail gracefully and be handled by the script.

ubuntu@dd1955ce2745:~$ sed -i '1a\\nunset DBUS_SESSION_BUS_ADDRESS' /etc/xdg/xfce4/xinitrc

Another Process Becomes Stuck

After fixing the first script, we find that another process becomes stuck. The command systemctl --user start xfce4-notifyd.service 2>/dev/null || exec /usr/lib/aarch64-linux-gnu/xfce4/notifyd/xfce4-notifyd is the offending command. This is run by /etc/xdg/autostart/xfce4-notifyd.desktop.

ubuntu@dd1955ce2745:~$ sed -i 's|^Exec=sh -c "systemctl --user start xfce4-notifyd.service.*|Exec=/usr/lib/aarch64-linux-gnu/xfce4/notifyd/xfce4-notifyd|' /etc/xdg/autostart/xfce4-notifyd.desktop

Workaround for Docker

To workaround this issue in a Docker container, we can add the following lines to the Dockerfile:

# Fixes for `systemctl --user` hanging on ARM64 architecture
RUN if [ "$(uname -m)" = "aarch64" ]; then \
        sed -i '1a\\nunset DBUS_SESSION_BUS_ADDRESS' /etc/xdg/xfce4/xinitrc && \
        sed -i 's|^Exec=sh -c "systemctl --user start xfce4-notifyd.service.*|Exec=/usr/lib/aarch64-linux-gnu/xfce4/notifyd/xfce4-notifyd|' /etc/xdg/autostart/xfce4-notifyd.desktop; \
    fi

Conclusion

In conclusion, the blank screen issue when RDP to ARM64 container on Ubuntu 22.04 and 24.04 is caused by the systemctl --user command hanging due to the DBUS_SESSION_BUS_ADDRESS variable being set. By adding unset DBUS_SESSION_BUS_ADDRESS at the start of the /etc/xdg/xfce4/xinitrc script and modifying the /etc/xdg/autostart/xfce4-notifyd.desktop script, we can fix this issue. Additionally, we can add a workaround to the Dockerfile to fix this issue in a Docker container.

References

systemd repository issue #36702
Blank Screen When RDP to ARM64 Container on Ubuntu 22.04 and 24.04: Q&A ====================================================================

Q: What is the blank screen issue when RDP to ARM64 container on Ubuntu 22.04 and 24.04?

A: The blank screen issue occurs when using Remote Desktop Protocol (RDP) to connect to an ARM64 container on Ubuntu 22.04 and 24.04. The problem is not present when using the same container on an AMD64 (x86_64) image.

Q: What causes the blank screen issue?

A: The blank screen issue is caused by the systemctl --user command hanging due to the DBUS_SESSION_BUS_ADDRESS variable being set. This variable is populated when a DBUS socket is created using eval "$(dbus-launch --sh-syntax)".

Q: How can I replicate the error?

A: To replicate the error, you can change to the ubuntu user account using su - ubuntu and then create a DBUS socket using eval "$(dbus-launch --sh-syntax)". This will populate the DBUS_SESSION_BUS_ADDRESS variable.

Q: How can I fix the issue?

A: To fix the issue, you can add unset DBUS_SESSION_BUS_ADDRESS at the start of the /etc/xdg/xfce4/xinitrc script. This will allow the systemctl --user commands to fail gracefully and be handled by the script.

Q: What is another process that becomes stuck?

A: Another process that becomes stuck is the command systemctl --user start xfce4-notifyd.service 2>/dev/null || exec /usr/lib/aarch64-linux-gnu/xfce4/notifyd/xfce4-notifyd. This is run by /etc/xdg/autostart/xfce4-notifyd.desktop.

Q: How can I fix the stuck process?

A: To fix the stuck process, you can modify the /etc/xdg/autostart/xfce4-notifyd.desktop script by removing the systemctl part of the command and leaving the exec command intact.

Q: How can I add a workaround to the Dockerfile?

A: To add a workaround to the Dockerfile, you can add the following lines:

# Fixes for `systemctl --user` hanging on ARM64 architecture
RUN if [ "$(uname -m)" = "aarch64" ]; then \
        sed -i '1a\\nunset DBUS_SESSION_BUS_ADDRESS' /etc/xdg/xfce4/xinitrc && \
        sed -i 's|^Exec=sh -c "systemctl --user start xfce4-notifyd.service.*|Exec=/usr/lib/aarch64-linux-gnu/xfce4/notifyd/xfce4-notifyd|' /etc/xdg/autostart/xfce4-notifyd.desktop; \
    fi

Q: Where can I report the issue?

A: You can report the issue to the systemd repository: https://github.com/systemd/systemd/issues/36702.

Q: What is the solution to the blank screen issue?

A: The solution to the blank screen issue is to add unset DBUS_SESSION_BUS_ADDRESS at the start of the /etc/xdg/xfce4/xinitrc script and modify the /etc/xdg/autostart/xfce4-notifyd.desktop script. Additionally, you can add a workaround to the Dockerfile to fix this issue in a Docker container.