Build Alpine image via Docker

[owenthereal]

I wonder whether anyone knows how to build an Alpine image via Docker similar to tools/docker/debian. I'm stuck at mounting the 9p filesystem

[SuperMaxusa]

Here is my proof-of-work Alpine Linux on 9pfs, feel free for suggestions.

1. Create Dockerfile

FROM i386/alpine:3.18.6

ENV KERNEL=lts
ENV HOSTNAME=localhost
ENV ROOT_PASSWORD=root

# Installing base packages, you can add additional packages here (community repo is enabled)
RUN apk add openrc alpine-base agetty alpine-conf

# Install newer mkinitfs from edge (todo: remove this when 3.19+ has worked properly with 9pfs)
RUN apk add mkinitfs --no-cache --allow-untrusted --repository https://dl-cdn.alpinelinux.org/alpine/edge/main/ 

# Installing kernel and remove unused drivers for linux-lts
RUN if [ "$KERNEL" == "lts" ]; then \
    apk add linux-lts linux-firmware-none; \
else \
    apk add linux-$KERNEL; \
fi

# Setting root password and hostname
RUN echo "root:$ROOT_PASSWORD" | chpasswd
RUN setup-hostname $HOSTNAME

# Enable autologin into root on tty1, also you can use autologin.c instead agetty
# (see https://wiki.alpinelinux.org/wiki/TTY_Autologin#By_compiling_your_own_autologin_wrapper)
RUN sed -i 's/getty 38400 tty1/agetty --autologin root tty1 linux/' /etc/inittab

# Adding networking.sh script (works only on lts kernel yet)
# (https://github.com/copy/v86/blob/master/tools/docker/debian/networking.sh)
RUN if [ "$KERNEL" == "lts" ]; then \ 
    echo -e "rmmod ne2k-pci && modprobe ne2k-pci\nhwclock -s\nsetup-interfaces -a -r" > /root/networking.sh && \ 
    chmod +x /root/networking.sh; \ 
fi

# Enable minimal needed OpenRC services
# (see https://wiki.alpinelinux.org/wiki/Alpine_Linux_in_a_chroot#Preparing_init_services)
RUN for i in devfs dmesg mdev hwdrivers; do rc-update add $i sysinit; done
RUN for i in hwclock modules sysctl hostname syslog bootmisc; do rc-update add $i boot; done
RUN rc-update add killprocs shutdown

# Generate initramfs with 9p modules
RUN mkinitfs -F "ata base ide scsi virtio ext4 9p" $(cat /usr/share/kernel/$KERNEL/kernel.release)

2. Create image container following by tools/docker/debian/build-container.sh

v86/tools/docker/debian/build-container.sh

Lines 11 to 16 in 360d569

	mkdir -p "$IMAGES"
	docker build . --platform linux/386 --rm --tag "$IMAGE_NAME"
	docker rm "$CONTAINER_NAME" || true
	docker create --platform linux/386 -t -i --name "$CONTAINER_NAME" "$IMAGE_NAME" bash
	docker export "$CONTAINER_NAME" > "$OUT_ROOTFS_TAR"

"$(dirname "$0")"/../../../tools/fs2json.py --exclude /.dockerenv --out "$OUT_FSJSON" "$OUT_ROOTFS_TAR"
# make sure that .dockerenv not included in fs.json (if this happened, remove it from "fsroot" in json)

v86/tools/docker/debian/build-container.sh

Lines 20 to 22 in 360d569

	# Note: Not deleting old files here
	mkdir -p "$OUT_ROOTFS_FLAT"
	"$(dirname "$0")"/../../../tools/copy-to-sha256.py "$OUT_ROOTFS_TAR" "$OUT_ROOTFS_FLAT"

3. Extract kernel and initrd

tar -zxf "$OUT_ROOTFS_TAR" --strip-components=1 boot/*-<lts or virt>

4. Add to V86 starter on your page (or use examples/arch.html):

  var emulator = new V86({
        ...
        bzimage: {
            url: "vmlinuz-...",
        },
        initrd: {
            url: "initramfs-...",
        },
        filesystem: {
            baseurl: "path/to/OUT_ROOTFS_FLAT/",
            basefs: "path/to/OUT_FSJSON",
        },
        bzimage_initrd_from_filesystem: false,
        cmdline: [
            "rw",
            "root=host9p rootfstype=9p rootflags=trans=virtio,cache=loose",
            "nowatchdog"
        ].join(" "),
    });

---

Notes:

• Alpine Linux v3.19.x is not working, it has some problems with writing files into 9p root, that ruined start some services in OpenRC use a 9286ca8 (you need build a v86 from wip branch)
• Firefox has a long startup problem, probably by Kernel hang with CONFIG_DEBUG_NMI_SELFTEST (Alpine Linux) #797
• For network, set networking_proxy url and run /root/networking.sh

[SuperMaxusa]

Yes, in Alpine Linux only branch v3.18 has kernel version 6.1.86-r0 at this moment: https://pkgs.alpinelinux.org/package/v3.18/main/x86/linux-lts

[progrium]

when I change the Dockerfile in wip for alpine to use 3.18, it fails to mount root. Anybody know what that's about?

[copy]

@progrium I can't reproduce this (although I had to use 3.18.3 since 3.18.1 wasn't downloading for me). Could you try:

• Show the output of lsmod
• modprobe virtio virtio_pci; mkdir -p /mnt; mount -t 9p host9p /mnt
• Delete the built files and rebuild from scratch

[SuperMaxusa]

when I change the Dockerfile in wip for alpine to use 3.18, it fails to mount root

If you use a 3.18.x, did you leave this line for installing mkinitfs from edge branch in Dockerfile?

v86/tools/docker/alpine/Dockerfile

Lines 14 to 15 in c69cbd7

	# Install mkinitfs from edge (todo: remove this when 3.19+ has worked properly with 9pfs)
	RUN apk add mkinitfs --no-cache --allow-untrusted --repository https://dl-cdn.alpinelinux.org/alpine/edge/main/

The repository for 3.18 contains an old version of mkinitfs, that doesn't have a 9p support (alpinelinux/mkinitfs@2a38df8, https://pkgs.alpinelinux.org/contents?file=9p.modules&name=mkinitfs&branch=v3.18).

[progrium]

Yes, it looks like I was slightly out of date, and using that Dockerfile with mkinitfs from edge fixed the problem. Thank you!