cf4f5be7ae
The desktop failed to start in a browser that had cached noVNC 1.6 from the Debian desktop image: its vnc.html, which has no clipboard Clear button, ran the Ubuntu image's 1.3 ui.js, which wires one up and threw "Cannot read properties of null". websockify sends only Last-Modified, so browsers cache noVNC on a guess, and it answers a revalidation with 304 when the file on disk is older than the copy. Serve noVNC through websockify-no-store, which adds Cache-Control: no-store to every response, and from /novnc/ rather than /, so no browser holds a stale copy at the paths the desktop now uses. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
38 lines
2.1 KiB
Docker
38 lines
2.1 KiB
Docker
# The exam's remote desktop: XFCE on Ubuntu 24.04 with a terminal and Firefox, served to the
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# browser over noVNC. It is the "base" machine of a session - no kubeconfig here; every task says
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# which host to ssh to.
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FROM docker.io/library/ubuntu:24.04
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ENV DEBIAN_FRONTEND=noninteractive LANG=C.UTF-8
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# Ubuntu's own firefox package only installs the snap, which cannot run in a container: Firefox ESR
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# comes from Mozilla's APT repository instead, pinned above Ubuntu's. Ubuntu's image has a user
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# `ubuntu` on uid 1000, which is the candidate's.
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RUN apt-get update \
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&& apt-get install -y --no-install-recommends ca-certificates curl \
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&& install -d -m 0755 /etc/apt/keyrings \
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&& curl -fsSL -o /etc/apt/keyrings/packages.mozilla.org.asc https://packages.mozilla.org/apt/repo-signing-key.gpg \
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&& echo 'deb [signed-by=/etc/apt/keyrings/packages.mozilla.org.asc] https://packages.mozilla.org/apt mozilla main' \
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> /etc/apt/sources.list.d/mozilla.list \
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&& printf 'Package: *\nPin: origin packages.mozilla.org\nPin-Priority: 1000\n' > /etc/apt/preferences.d/mozilla \
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&& userdel -r ubuntu \
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&& apt-get update \
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&& apt-get install -y --no-install-recommends \
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xfce4 xfce4-terminal dbus-x11 elementary-xfce-icon-theme greybird-gtk-theme \
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fonts-dejavu fonts-liberation \
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tigervnc-standalone-server novnc websockify \
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firefox-esr mousepad xclip \
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openssh-client sudo vim nano less jq tmux curl wget bash-completion ca-certificates \
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procps iputils-ping dnsutils \
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&& rm -rf /var/lib/apt/lists/*
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COPY rootfs/ /
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RUN useradd -m -s /bin/bash -u 1000 candidate \
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&& echo 'candidate ALL=(ALL) NOPASSWD:ALL' > /etc/sudoers.d/candidate && chmod 440 /etc/sudoers.d/candidate \
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&& install -d -o candidate -g candidate /home/candidate/.config/xfce4/xfconf/xfce-perchannel-xml \
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&& install -m644 -o candidate -g candidate /etc/xdg/xfce4/panel/default.xml \
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/home/candidate/.config/xfce4/xfconf/xfce-perchannel-xml/xfce4-panel.xml \
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&& ln -s /usr/share/novnc /srv/novnc \
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&& chmod +x /usr/local/bin/start-desktop /usr/local/bin/websockify-no-store
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USER candidate
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WORKDIR /home/candidate
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EXPOSE 6080
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ENTRYPOINT ["/usr/local/bin/start-desktop"]
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