Install Alpine on Rackspace

This material needs expanding ... This article is not compatible with posix shell but should be since alpine uses ash by default

Create a minimal rackspace server

Debian 7

512MB, 20GB

Copy settings from existing server into apkovl

The first step is to create Alpine configuration file with basic configuration of the host. We need the new box to start networking and ssh in the beginning so we can reconnect to it after reboot.

Create basic layout for the overlay:

mkdir overlay
cd overlay
mkdir -p etc/ssh etc/network etc/runlevels/{default,boot,sysinit,shutdown} root/.ssh etc/lbu etc/apk

If you want to keep the existing host identity (e.g. SSH key), you can copy them over:

cp -a /etc/{passwd,group,shadow,gshadow,hostname,network/interfaces,ssh} etc/
cp /etc/network/interfaces etc/network
echo "nameserver 8.8.8.8" > etc/resolv.conf

Copy over your ssh authorized_keys and make sure its included in future:

cp -a /root/.ssh/authorized_keys root/.ssh
echo "/root/.ssh" > etc/lbu/include

Edit etc/passwd and change bash to /bin/sh.

sed -i -e '/^root:/s:/bin/bash:/bin/sh:' etc/passwd

Note: If you don't do this, nobody (even with physical access) will be able to log into the machine.

Make sure there is no whitespace at end of lines in interfaces file. Busybox ifup is very picky.

sed -i -e 's/ *$//' etc/network/interfaces

Create the apk world (/etc/apk/world) with essential packages:

echo "alpine-base iproute2 openssh bash" > etc/apk/world

(bash is technically not needed, but include it in case you forgot to edit your etc/passwd file correctly)

Double check the IP configuration and ssh keys.

Finally, make the essential services start up automatically and create the overlay file:

ln -s /etc/init.d/{hwclock,modules,sysctl,hostname,bootmisc,syslog} etc/runlevels/boot/
ln -s /etc/init.d/{devfs,dmesg,mdev,hwdrivers} etc/runlevels/sysinit/
ln -s /etc/init.d/{networking,sshd} etc/runlevels/default/
ln -s /etc/init.d/{mount-ro,killprocs,savecache} etc/runlevels/shutdown/
tar czf ../host.apkovl.tar.gz *

Verify the overlay with "tar tzf" to see that it contains everything in proper places, and ensure it is in the / directory

tar tzvf ../host.apkovl.tar.gz
cp ../host.apkovl.tar.gz /

Install Alpine cd-rom image to hard disk

We need to copy over two sets of information: the boot kernel (kernel, initramdisk and boot configuration) and operating system boot data (overlay, apk packages and kernel modules).

Download an alpine iso and mount it; for example

 wget https://dl-3.alpinelinux.org/alpine/v3.2/releases/x86_64/alpine-xen-3.2.2-x86_64.iso
 # We will grab the sha512 sum from another mirror
 wget https://nl.alpinelinux.org/alpine/v3.2/releases/x86_64/alpine-xen-3.2.2-x86_64.iso.sha512
 sha512sum -c alpine-xen-3.2.2-x86_64.iso.sha512 
 mkdir /cdrom
 mount alpine*.iso /cdrom -o loop

Copy the contents of cd-rom image to root of current installation, then setup grub:

cp -a /cdrom/* /
mkdir /cache
umount /cdrom

cat - >/boot/grub/grub.cfg <<EOF 
set default="0"
set timeout="3"

menuentry "Alpine Linux" {
	insmod gzio
	insmod part_msdos
	insmod ext2
	set root='(hd0,msdos1)'
	linux /boot/vmlinuz-grsec root=$(blkid /dev/xvda1 | awk '{ print $2 }' | sed 's/"//g') modules=sd-mod,usb-storage,ext3 quiet
        initrd /boot/initramfs-grsec
}
EOF

Warning: In Alpine 3.2 and earlier the Xen ISO image does not include openssh. Follow these instructions if you want to be able to remotely ssh into your box.

Download the base iso and copy the apks

wget https://dl-3.alpinelinux.org/alpine/v3.2/releases/x86_64/alpine-3.2.2-x86_64.iso
# We will grab the sha512 sum from another mirror
wget https://nl.alpinelinux.org/alpine/v3.2/releases/x86_64/alpine-3.2.2-x86_64.iso.sha512
sha512sum -c alpine-3.2.2-x86_64.iso.sha512 
mount alpine-3*.iso /cdrom -o loop
cp -a /cdrom/apks/* /apks

Reboot and check that all came back as expected.

Cleanup

Once your server comes back, you are good to go. However, the old Debian system is still on xvda1; and ipv6 is not enabled. These optional steps will fix that:

Enable ipv6

echo "ipv6" >> /etc/modules
modprobe ipv6

You can either reboot or restart networking (and re-log in).

Clear out old stuff:

mount /media/UUID* -o remount,rw
cd /media/UUID*
rm -rf $( find -type d -maxdepth 1 | grep -v 'apks' | grep -v 'boot' | grep -v 'lost+found' )
# the above command will take a while
rm *.iso
find -type l -exec rm {} \;
rm $( find boot  -maxdepth 1 -type f | grep -v grsec)
# Now we blank out the disk - this will take a long time
dd if=/dev/zero of=foo
rm foo
sync

reboot and you should be good to go.