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Reinstalling system leaving home intact
Currently working as a Senior Consultant at Netcompany spending my full-time job solving the SharePoint riddles. In the free time I'm expanding my understanding of cybersecurity through hacking activities. Git fanboy.
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💡 This write-up is a part of the HTB Sherlocks series. Sherlocks are investigative challenges that test defensive security skills. I encourage you to try them out if you like digital forensics, incident response, post-breach analysis and malware ana...
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💡 This write-up is a part of the HTB Sherlocks series. Sherlocks are investigative challenges that test defensive security skills. I encourage you to try them out if you like digital forensics, incident response, post-breach analysis and malware ana...
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Please note that following approach works only when Linux was installed previously with a separate
/homepartitionThis guide assumes you know how to install the Linux already. If not, please refer to previous article.
I'm using the Kali installer but steps should be same regardless the Linux flavour
Story starts when I tried to get my CUDA working with a hashcat. I have installed video card drivers and tools with apt get install nvidia-driver nvidia-cuda-tools which leads to some serious issues that prevent me from logging into my installation.
I haven't found the complete guide on how to reinstall the system, leaving the /home (or simply any other) partition intact. So, whoever may want to do the same, here is what I did.
Verify the checksum of downloaded file with the one presented on the download page
Can't confirm if you have to choose the same values as it was on original installation, but it shouldn't matter. Let me know in the comments if that causes some issues on you
/home data, leave the volumes size as it is. Choose to format every partition, but do not format home.
/home, make double sure you are not formatting it.
Ext4 and /boot mount point.
You can keep the existing data, because the encrypted volume itself does not change, only the LVM it contains.
This is how the partitioning schema looks like before changes are committed.
Now continue with the installation.
crypttableAfter the booting on fresh system, Grub won't recognize/discover the encrypted volume, and it fails booting. It can show that device is not available or simply show initramfs prompt. Reason is that installer is not updating the /etc/crypttab file - probably because during the partitioning step, we actually didn't configure the encrypted partition; it was unlocked already before we entered the partitioning screen. To fix that, perform the following steps. Original author of this is Halacs from superuser.com.
At the time of writing default credentials are
kali/kali.
sudo su./boot and encrypted LVM. You will recognize file system by its size.
$ cryptsetup luksOpen /dev/sda6 gabor2-crypt
If you care of naming your encrypted volume (it will be visible on passphrase prompt each boot) change the
gabor2-cryptto your liking and use that name consistently during further steps.
fdisk -l and lsblk
/mnt to mount all new system and boot partitions. You will be switching root to the /mnt later, so it is important to keep all mount points in the single folder.mount /dev/mapper/kali--vg-root /mnt
mount /dev/mapper/kali--vg-home /mnt/home
mount /dev/mapper/kali--vg-var /mnt/var
mount /dev/mapper/kali--vg-tmp /mnt/tmp
mount /dev/sda5 /mnt/boot
lsblk
mount --bind /dev /mnt/dev
mount --bind /run /mnt/run
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
/mnt.chroot /mnt
chrooted scope, all commands are performed on the newly installed systemcrypttab.blkid /dev/sda6
crypttab.$ nano /etc/crypttab
gabor2-crypt UUID="f8da3b2d-c0d4-4d02-b45d-9917adf31931" none luks
Please note that this is not copy-paste from previous step.
update-initramfs -u
update-grub
Watch out for warning messages, when device label in
/etc/crypttabdoes not match current label of decoded LUKS. If that happen, please ensure the name in/etc/crypttaband name of encrypted volume are the same.
chroot scope, unmount all devices and close LUKS.exit
umount -R /mnt
vgchange -a n
cryptsetup luksClose gabor2-crypt
Now your system should show passphrase prompt and boot to login screen. Unfortunately, you can't login to your user because it does not exist yet on the new system.
If you are using the system that doesn't block root account password login, you can skip the next section.
root shell
E. Search for the line starting with linux.
rw quiet init=/bin/bash. Press F10.
useradd --no-create-home -d /home/asentinn -s /bin/bash asentinn
chown -R asentinn:asentinn /home/asentinn
sudo -l -U asentinn
passwd asentinn
