Replacing non-Alpine Linux with Alpine remotely: Difference between revisions
(→Create apk overlay suitable for hard disk based tmpfs boot: commands for creating var/lib/world) |
(→Install Alpine cd-rom image on hard disk: note about /usr/lib/syslinux on older systems) |
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Next we make the Alpine Linux kernel bootable (requires syslinux) and use fdisk to mark the /boot partition as bootable (if not done already): | Next we make the Alpine Linux kernel bootable (requires syslinux) and use fdisk to mark the /boot partition as bootable (if not done already): | ||
cp -a /cdrom/boot/grsec{,.gz} /boot | cp -a /cdrom/boot/grsec{,.gz} /boot | ||
dd if=/usr/share/syslinux/mbr.bin of=/dev/hda | dd if=/usr/share/syslinux/mbr.bin of=/dev/hda # on some older systems its /usr/lib/syslinux/mbr.bin | ||
fdisk /dev/hda | fdisk /dev/hda | ||
Revision as of 14:04, 16 September 2009
Instructions to replace running Linux installation with Alpine Linux, remotely using ssh connection only.
Tested using alpine-1.9.0_rc2.
CAUTION: Practice on a computer with physical access first. If something goes wrong, the remote box will very likely be left into unusable state.
Prerequisites:
- SSH access to the remote box (needs to have SSH server running)
- Alpine Linux supported hardware
- Adventurous mind
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 etc/runlevels/boot root/.ssh
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/
If you copy over passwd, replace default shell to be /bin/sh for everyone. You might also end up with inconsistent user/group id's for standard Alpine Installation. Consider copying passwd, group and shadow from a running Alpine Linux box. You can also just use all default config files for passwd etc. Then you must use ssh key to authorize yourself (as root password is empty, and ssh has empty passwords disabled).
Copy over your ssh authorized_keys:
cp -a my_authorized_keys root/.ssh
The file network/interfaces might not necessarily exists. Some distributions use different configuration file for network. If it does not exists, you need to create it. It should look something like:
auto lo iface lo inet loopback auto eth0 iface eth0 inet static address ip.ad.dr.es netmask 255.255.255.0 gateway gw.ad.dr.es
Create the apk world (var/lib/apk/world) with essential packages:
mkdir -p var/lib echo "alpine-base iproute2 openssh" > var/lib/world
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/hostname etc/runlevels/boot/hostname ln -s /etc/init.d/bootmisc etc/runlevels/default/bootmisc ln -s /etc/init.d/networking etc/runlevels/default/networking ln -s /etc/init.d/sshd etc/runlevels/default/sshd tar czf ../host.apkovl.tar.gz *
Verify finally the overlay with "tar tzf" to see that it contains everything in proper places.
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 hda1 (/boot) and hda2 (/) with both having ext3 filesystems.
We start with the easy task. Place the overlay file and the "apks" directory from cd-rom image to root of current installation:
cp host.apkovl.tar.gz / cp -a /cdrom/apks / cp -a /cdrom/boot/grsec.cmg /
Next we make the Alpine Linux kernel bootable (requires syslinux) and use fdisk to mark the /boot partition as bootable (if not done already):
cp -a /cdrom/boot/grsec{,.gz} /boot dd if=/usr/share/syslinux/mbr.bin of=/dev/hda # on some older systems its /usr/lib/syslinux/mbr.bin fdisk /dev/hda
Create /boot/extlinux.conf with contents like (alpine_dev needs special care, generally hard-disks are sd* in alpine due to new kernel and libata; you also need to check the filesystem type; kernel and initrd are relative to partition root):
timeout 20 prompt 1 default grsec label grsec kernel /grsec append initrd=/grsec.gz alpine_dev=sda2:ext3 modloop=grsec.cmg modules=loop,cramfs,sd-mod,usb-storage,ext3 quiet
Finally make the /boot partition bootable by extlinux.
extlinux -i /boot
Install Alpine on hard-disk
Reboot, the box. And wait for it to come alive again. If it doesn't, tough luck. So dry practice with local box, with as identical hardware as possible.
Once back in the box, we are running in Alpine Linux from tmpfs. So just do a regular installation of Alpine from network via ssh connection.
Edit /etc/apk/repositories to contain your favorite Alpine mirror or just:
http://dl-3.alpinelinux.org/alpine/v1.9/packages/main
Finally run:
/etc/init.d/modloop stop apk update setup-disk
Reboot once more, and you have the server with native Alpine hard disk installation.