rework the repo to enable more images

README.md

@@ -1,28 +1,47 @@
-# Alpine to image builder
+# Rootfs image builder
 
-This repo builds an `ext4` or an `initrd` based on an Alpine image.
+This repo builds an `ext4` or an `initrd` using Docker containers.
 
 Note: *some assembly required.*
 
 ## Building a rootfs
 
-1. Customize `docker_rootfs_builder` to add custom list of packages.
-Here you can install anything that you need in the final image.
-2. Customize `alpine_boot` to run a startup script.
-3. Run `./build_rootfs.sh`.
+Simply run:
+
+```bash
+./build-rootfs.sh <rootfs-type>
+```
+
+Where `rootfs-type` is one of the root filesystem generators that starts with `type-`.
+
+For example, to generate an `Ubuntu 21.04` rootfs, run:
+
+```bash
+./build-rootfs.sh ubuntu21.04
+```
 
 ## Building an initrd
 
-1. Customize `docker_rootfs_builder` to add custom list of packages.
-Here you can install anything that you need in the final image.
-2. Customize `alpine_boot` to run a startup script.
-3. Run `./build_initrd.sh`.
+The initrd is
+
+## Customizing the build process
 
-## Utils
+Each rootfs generator consists of 3 files:
 
-`ext4_to_initrd.sh rootfs.ext4` converts an ext4 rootfs to an initrd
+- `init-rootfs.sh`: creates the root filesystem and formats it.
+This is needed because a distribution may take a larger amount of space
+
+- `inside-container.sh`: what is installed in a rootfs.
+Here this script usually finishes with copying the rootfs contents to a mounted rootfs.ext4 file.
+
+- `run-container.sh`: controls the container lifetime. For example the Ubuntu container is started
+twice because systemd needs to be initialized.
+
+### Adding a new image type
+
+Just add a new folder with the 3 files described above
 
 ## Troubleshooting
 
-- Need a larger image? Change `build_rootfs.sh`.
-- Need to run something at startup? Change `alpine_boot`
+- Need a larger image? Change `init-rootfs.sh`.
+

build-initrd.sh

@@ -0,0 +1,8 @@
+#!/bin/bash
+# Build an initrd from alpine
+set -e
+
+SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+
+"$SCRIPT_DIR"/build-rootfs.sh alpine
+"$SCRIPT_DIR"/utils/ext4_to_initrd.sh rootfs.ext4

build-rootfs.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+set -e
+SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+RPATH="$SCRIPT_DIR/rootfs.ext4"
+
+if [ $UID != 0 ]; then
+    echo "Needs root"
+    exit 1
+fi
+
+if [[ ! -d "$SCRIPT_DIR/type-$1" ]]; then
+    types=`ls -d1 ./type* | cut -d'-' -f2`
+    echo -e "$1 is not a rootfs type. Try one of:\n$types"
+fi
+
+# Clean up old files
+if [[ -f "$RPATH" ]]; then
+    rm -rf "$RPATH"
+fi
+
+"type-$1/init-rootfs.sh" "$RPATH"
+"type-$1/run-container.sh" "$RPATH"

type-alpine/init-rootfs.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Create the rootfs and format it
+dd if=/dev/zero of="$1" bs=1M count=50 > /dev/null
+mkfs.ext4 "$1" > /dev/null

docker_rootfs_builder → type-alpine/inside-container.sh

@@ -1,24 +1,18 @@
 #!/bin/sh
-
+set -e
 # Based on:
 # https://github.com/firecracker-microvm/firecracker/blob/master/docs/rootfs-and-kernel-setup.md
 
-### Common
+### Customize me!
 apk add openrc
 apk add util-linux
 
-###
-
-### Customize me!
-# Build stuff
-apk add vim iperf3 fio bash dropbear haveged
+# Set up ssh access
+apk add bash dropbear haveged
 mkdir -p /etc/dropbear
 rc-update add haveged
 ###
 
-### Optional: Working dir
-# mkdir -p /work
-
 ### Post install stuff
 # Set up a login terminal on the serial console (ttyS0):
 ln -s agetty /etc/init.d/agetty.ttyS0
@@ -39,12 +33,31 @@ rc-update add sysfs boot
 # Enable local.d scripts
 rc-update add local default
 
-# Optional: copy startup script
-cp /alpine_boot /etc/local.d/RunMe.start
+# Create startup script
+cat <<EOF > /etc/local.d/RunMe.start
+# Mount ramfs in /tmp
+mkdir /tmp
+mount -t tmpfs tmpfs /tmp
+
+# Create an overlayfs over /etc
+# dropbear uses /etc to create keys
+mkdir -p /tmp/etc/work
+mkdir -p /tmp/etc/upper
+
+mount -t overlay \
+      -o lowerdir=/etc,upperdir=/tmp/etc/upper,workdir=/tmp/etc/work \
+       overlay /etc
+
+dropbear -RBE&
+EOF
 
 # Then, copy the newly configured system to the rootfs image:
+mkdir /my-rootfs
+mount /rootfs.ext4 /my-rootfs
+
 for d in bin etc lib root sbin usr; do tar c "/$d" | tar x -C /my-rootfs; done
 for dir in dev proc run sys var tmp; do mkdir /my-rootfs/${dir}; done
+umount /my-rootfs
 
 # All done, exit docker shell
 exit

type-alpine/run-container.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+set -e
+SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+
+# Launch the container
+cont_id=$(docker run -td --rm  --privileged -v $1:/rootfs.ext4 alpine)
+
+# Run the payload
+set +e
+docker exec -it "$cont_id" /bin/sh -c "`cat $SCRIPT_DIR/inside-container.sh`"
+
+rval=$?
+set -e
+
+# Stop the container
+docker stop "$cont_id"
+
+if [[ "$rval" != 0 ]]; then
+    echo "Error running the payload"
+    exit 1
+fi

type-amazonlinux2/init-rootfs.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Create the rootfs and format it
+dd if=/dev/zero of="$1" bs=1M count=800 > /dev/null
+mkfs.ext4 "$1" > /dev/null

type-amazonlinux2/inside-container.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+set -e
+### Customize me!
+yum install -y \
+      openssh-server \
+      openssh-clients \
+      iproute2 \
+      net-tools \
+      tar \
+      procps
+
+# Set password
+echo "root:root" | chpasswd
+
+# Start the ssh server to generate keys
+systemctl start sshd
+
+# Then, copy the newly configured system to the rootfs image:
+mkdir /my-rootfs
+mount /rootfs.ext4 /my-rootfs
+
+for d in bin etc lib lib64 root run sbin usr var; do tar c "/$d" | tar x -C /my-rootfs; done
+for dir in dev proc run sys var tmp; do mkdir -p /my-rootfs/${dir}; done
+umount /my-rootfs
+
+# All done, exit docker shell
+exit

type-amazonlinux2/run-container.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+set -e
+SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+
+# Launch the container
+cont_id=$(docker run -td --rm  --privileged -v $1:/rootfs.ext4 amazonlinux:2)
+
+# Install systemd
+docker exec -it "$cont_id" /bin/bash -c "yum install -y systemd"
+
+# Restart the container
+docker commit "$cont_id" "temp-build-amazonlinux"
+docker stop "$cont_id"
+new_cont_id=$(docker run -td --rm  --privileged -v $1:/rootfs.ext4 temp-build-amazonlinux /sbin/init)
+
+# Run the payload
+set +e
+docker exec -it "$new_cont_id" /bin/sh -c "`cat $SCRIPT_DIR/inside-container.sh`"
+
+rval=$?
+set -e
+
+# Stop the container
+docker stop "$new_cont_id"
+docker rmi -f "temp-build-amazonlinux"
+
+if [[ "$rval" != 0 ]]; then
+    echo "Error running the payload"
+    exit 1
+fi

type-ubuntu21.04/init-rootfs.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Create the rootfs and format it
+dd if=/dev/zero of="$1" bs=1M count=800 > /dev/null
+mkfs.ext4 "$1" > /dev/null

type-ubuntu21.04/inside-container.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+set -e
+### Customize me!
+DEBIAN_FRONTEND="noninteractive" apt-get install -y \
+      openssh-server \
+      openssh-client \
+      iproute2 \
+      net-tools strace
+
+# Enable SSH
+echo "PermitRootLogin yes" >> /etc/ssh/sshd_config
+
+# Set password
+echo "root:root" | chpasswd
+
+# Set up serial
+systemctl enable getty@ttyS0
+systemctl start getty@ttyS0
+
+# Then, copy the newly configured system to the rootfs image:
+mkdir /my-rootfs
+mount /rootfs.ext4 /my-rootfs
+
+for d in bin etc lib lib64 root run sbin usr var; do tar c "/$d" | tar x -C /my-rootfs; done
+for dir in dev proc run sys var tmp; do mkdir -p /my-rootfs/${dir}; done
+umount /my-rootfs
+
+# All done, exit docker shell
+exit

type-ubuntu21.04/run-container.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+set -e
+SCRIPT_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
+
+# Launch the container
+cont_id=$(docker run -td --rm  --privileged -v $1:/rootfs.ext4 ubuntu:21.04)
+
+# Install systemd
+docker exec -it "$cont_id" /bin/bash -c "apt-get update && DEBIAN_FRONTEND='noninteractive' apt-get install -y systemd"
+
+# Restart the container
+docker commit "$cont_id" "temp-build-ubuntu"
+docker stop "$cont_id"
+new_cont_id=$(docker run -td --rm  --privileged -v $1:/rootfs.ext4 temp-build-ubuntu /usr/bin/systemd)
+
+# Run the payload
+set +e
+docker exec -it "$new_cont_id" /bin/sh -c "`cat $SCRIPT_DIR/inside-container.sh`"
+
+rval=$?
+set -e
+
+# Stop the container
+docker stop "$new_cont_id"
+docker rmi -f "temp-build-ubuntu"
+
+if [[ "$rval" != 0 ]]; then
+    echo "Error running the payload"
+    exit 1
+fi