Fully functional rescue initramfs for Debian based OS. Experimental! I'd recommend you to test these scripts on VM first, i.e. using https://github.com/kayrus/deploy-vm

Please note the the whole boot disk will be wiped!

• Copy scripts into destination VM
• Run sudo ./run_in_os.sh (you have to use sudo and current user's ~/.ssh/authorized_keys will be used)
• Reboot the VM
• Login using root user (if you won't login within 60 secounts, the normal boot will be initiated)

• Run deploy_os.sh to install the VMWare Ubuntu Xenial image into the /dev/?da block device
• Reboot the VM to boot the new OS: echo b > /proc/sysrq-trigger
• After the reboot you have to use ubuntu ssh user with your private key.

If you wish to install Ubuntu Trusty with LVM, please run the command below:

deploy_os_lvm.sh /dev/sda trusty

After the reboot you have to use ubuntu ssh user with your private key.

• Run deploy_os_lvm.sh to install the Ubuntu Xenial bootstrap files into the /dev/?da block device with LVM layout
• After the reboot you have to use ubuntu ssh user with your private key.

This script doesn't support RedHat based OS. In case when you would like to boot into rescue-initramfs from RadHat OS you have to use some tricks:

• Generate (run sudo ./run_in_os.sh) initramfs image on some test VM (which runs linux-image-virtual image).
• On the target host rename the original /boot/initramfs-*.img and /boot/vmlinuz-* to *_bak. In case when there are several initramfs files, try to find one which corresponds to the first GRUB menu entry inside the /boot/grub/grub.conf file.
• Copy generated initrd* along with the vmlinuz-* into the target's /boot directory using the names which were used by the original files.
• Make a backup of the original grub config (/boot/grub/grub.conf). Modify grub config and append proper ip=${IP}::${GATEWAY}:${NETWORK}:${HOSTHAME}:eth0:off along with the break=mount net.ifnames=0 biosdevname=0 console=ttyS0 console=tty1 at the end of all strings which start with the kernel.
• From grub config remove stuff like: rd_LVM_LV=vglocal20140422/root00 rd_LVM_LV=vglocal20140422/swap00 rd_NO_LUKS pci=bfsort LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM rhgb quiet
• Verify IP address, path's to kernel and initrd.
• Run the ping command to monitor the server availability status.
• Reboot and pray that VM with rescue-initramf will boot.
• You have 60 seconds from the beginning to log in into the rescue console, so please prepare the ssh root@%IP% command in the different terminal window.

If you don't want to install Ubuntu image, but just modify/resize filesystems and then reboot, you have to restore original initrd and linux image along with the grub config before the reboot.

• Implement support for several authorized_keys entries
• Implement mdadm support

In case of problems you can download initial Ubuntu's bootstrap fs and chroot into it to get access to the full Ubuntu environment for further investigation:

mkdir -p /mnt
curl https://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-root.tar.xz | tar -xJf - -C /mnt
mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt bash

mdadm --stop /dev/md0
mdadm --remove /dev/md0
mdadm --zero-superblock /dev/sda
mdadm --zero-superblock /dev/sdb

Dropbear in Ubuntu Trusty doesn't support ECDSA, but OpenSSH supports it. Thus you can face known_hosts problem when RSA/DSS keys are used in Dropbear instead of ECDSA.

Inspired by:

• https://blog.tincho.org/posts/Setting_up_my_server:_re-installing_on_an_encripted_LVM/

• Make sure there is no VG with the same name