Install Alpine on Rackspace

Create a minimal rackspace server

Debian 7

512MB, 20GB

Create apk overlay suitable for hard disk based tmpfs boot

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

You can also use default Alpine configuration files. In this case you should use ssh key to authorize yourself (as root password is empty, and ssh has empty passwords disabled).

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,resolv.conf,network/interfaces,ssh} etc/
cp /etc/network/interfaces etc/network

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

Find out which shell is used for root:

grep ^root /etc/passwd

If its /bin/sh, you are good. If not, edit etc/passwd and change it 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.

Make sure your etc/resolv.conf exists; if not create etc/resolv.conf with the nameserver configuration like:

nameserver dns.ip.ad.dr

Create the apk world (var/lib/apk/world) with essential packages:

mkdir -p var/lib/apk
echo "alpine-base iproute2 openssh bash" > var/lib/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 on 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). These can reside on same partition if they fit. However, /boot is usually small, so you might want to put the apks on separate partition. This guide assumes they are on sda1 (/boot) and sda2 (/) with both having ext3 filesystems. If you don't have ext3 on / or /boot, then you might be able to disable swap and reformat the swap partition as ext3 and use that.

Download an alpine iso and mount it; for example

 wget http://dl-4.alpinelinux.org/alpine/v2.6/releases/x86_64/alpine-2.6.2-x86_64.iso
 mkdir /cdrom
 mount alpine*.iso /cdrom -o loop

Copy the apkovl and the contents of cd-rom image to root of current installation:

cp host.apkovl.tar.gz /
cp -a /cdrom/* /

mkdir -p /boot/grub
cat - >target/boot/grub/grub.conf <<EOF 
default=0
timeout=3
hiddenmenu

title Alpine Linux
root (hd0)
kernel /boot/grsec alpine_dev=xvda1:ext3 modules=loop,squashfs,sd-mod,ext3 console=hvc0 pax_nouderef BOOT_IMAGE=/boot/grsec
initrd /boot/grsec.gz
EOF

• Syslinux automatically adds BOOT_IMAGE to the kernel command line; grub does not, so make sure you specify it in the grub.conf
• You do not need any other grub files - just boot.conf

ln -sf ./grub.conf target/boot/grub/menu.lst

Reboot