I have a Linux system and I wish to install CentOS 7 alongside it. The problem is that I cannot boot from an install medium.

Can I install CentOS without the installation system, or start the installation system from a different Linux?

Installing grub won't be the biggest issue, it is already there and I can hand-edit a new entry. Problem is the file system entry creation and installation (think Arch install).

  • I don't know much about CentOS tho but Debian/Ubuntu has debootstrap for that, Arch has something similar with pacstrap maybe this gives you a direction.
    – Videonauth
    Nov 7 '17 at 20:08
  • 1
    VMs can usually boot into anything. Nov 7 '17 at 20:12
  • @IgnacioVazquez-Abrams Thanks, that may be a way, will try.
    – Ned64
    Nov 8 '17 at 7:57

Yes you can Install a system without installation media. An installer basically generates binary files, drivers and configurations depending on your hardware and copy them into a partition. As you've issue with installer you can copy all files from a installed system to a partition where you want to install CentOS.

Freshly install CentOS to an approximately similar hardware as Minimal Installation. Don't update the newly installed system. Keep the freshly installed machine on. Create a new partition in destination system and temporarily mount it in /mnt/new folder. Copy all contents of / partition of fresh installation with rsync to the new partition where you want to install CentOS. Use -avz flag with rsync as root user. Exclude proc, /dev, /sys, /run directory with --exclude with rsync.

sudo rsync -avz root@newsystem:/* /mnt/new/ --exclude '/dev' --exclude '/proc' --exclude '/sys' --exclude '/run'

Now create those excluded directories in new system.

sudo mkdir /mnt/new/sys /mnt/new/dev /mnt/new/proc /mnt/new/run

Now edit /etc/fstab and mount file-system properly. Make proper grub entry and boot the system with newly copied CentOS. If the system unfortunately leave you in dracut shell use the command blkid to find UUID of partitions. Identify UUID of your new root partition. Reboot to previously running system and edit /etc/fstab with UUID instead /dev/sda1 etc.

If still it's leaving in dracut shell boot the system with rescue kernel and rescue initramfs and regenerate initramfs for your hardware. Now it shall work.

You may install fresh CentOS inside virtualbox on the running system and copy CPU configuration etc. from host. Then copy that installation to desired partition in host.

Most issues occurs while transferring a Linux installation is with display driver and fstab entry. So Transfer a minimal installation only. Latter install X Server and Gnome etc.

  • Sorry for the late accept, couldn't test earlier!
    – Ned64
    Apr 3 '20 at 16:51

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