Fix AlmaLinux RAID1: No Bootable Device Detected

Introduction

Hey guys! Ever run into that frustrating situation where you've meticulously set up your RAID array, installed your OS, and then... nothing? You're greeted with the dreaded "No bootable devices detected" message? Yeah, it's a real head-scratcher. This article dives deep into troubleshooting an AlmaLinux installation on an mdadm RAID1 array that fails to boot. We'll break down the common causes and walk through the steps to get your system up and running. We aim to make this guide super helpful, so you can confidently tackle RAID setups with AlmaLinux. If you're facing this issue, you're definitely in the right place. Let's get started and figure this out together!

Understanding the Problem: Why "No Bootable Devices"?

Okay, so you've installed AlmaLinux on your RAID1 array, but your system isn't booting. The "No bootable devices detected" error is a common issue, but what's actually going on? The core of the problem lies in the boot process. When your computer starts, it needs to find a bootloader – a small program that knows how to load your operating system. In a RAID setup, especially with mdadm, this process can get a little tricky. The BIOS or UEFI needs to recognize the RAID array, and the bootloader needs to be installed in a way that it can be accessed from the RAID. Several things can go wrong here. Maybe the bootloader wasn't installed on the RAID array itself, or perhaps the BIOS isn't configured to boot from the RAID. It could also be an issue with the initramfs, which is a small file system used during the boot process to load necessary drivers (like those for RAID) before the main system takes over. We will cover common causes such as incorrect bootloader installation, BIOS/UEFI settings, missing RAID drivers in initramfs, and Grub configuration errors. To really nail down the cause, we need to systematically investigate each of these possibilities. So, let’s dive into the common culprits and how to check them out!

Diagnosing the Issue: Key Areas to Investigate

Alright, let's put on our detective hats and figure out why your AlmaLinux installation isn't booting from the RAID1 array. We're going to focus on the key areas that often cause this hiccup. First up, we need to double-check the bootloader installation. This is a big one. The bootloader (usually GRUB in AlmaLinux) needs to be correctly installed on the RAID array, not just a single disk. If it’s only on one disk and that disk fails, or the system tries to boot from the other disk, you're going to run into problems. Next, we'll peek into your BIOS or UEFI settings. These settings tell your computer the order in which to check for bootable devices. If your RAID array isn't listed or isn't the first in the boot order, the system won't even try to boot from it. Another critical area is the initramfs. This is a small file system that loads early in the boot process and contains essential drivers. If the RAID drivers aren't included in the initramfs, your system won't be able to recognize the RAID array during boot. Lastly, we'll look at the GRUB configuration. A misconfigured GRUB can prevent the system from locating the kernel and booting correctly. So, we'll explore these areas step-by-step, providing you with the tools to diagnose and, more importantly, fix the issue. Let's get to it!

1. Verifying Bootloader Installation

The bootloader is the unsung hero that gets your operating system up and running. In AlmaLinux, GRUB is the usual suspect. Making sure GRUB is correctly installed on your RAID1 array is crucial. If it's installed on just one drive, your system will fail to boot if that drive has issues or if the BIOS tries to boot from the other drive. So, how do we check this? First, you'll need to boot into a rescue environment. You can do this using your AlmaLinux installation media. Once you're in the rescue environment, you can use mdadm commands to check the status of your RAID array. For example, mdadm --detail /dev/md0 (replace /dev/md0 with your RAID device) will give you a detailed look at your array, including which drives are part of it and their status. Next, you'll want to mount your RAID array. This allows you to access the files inside. You might need to create a mount point first (e.g., mkdir /mnt/sysroot), and then mount your root partition (e.g., mount /dev/md0 /mnt/sysroot). Once mounted, you can use grub2-install to install GRUB onto the RAID array. It's super important to specify the correct device here – you want to target the RAID device itself (e.g., /dev/md0), not individual disks (e.g., /dev/sda). After installation, you might also need to regenerate the GRUB configuration file using grub2-mkconfig -o /mnt/sysroot/boot/grub2/grub.cfg. This ensures that GRUB knows how to find your kernel and initramfs. Verifying the bootloader installation properly sets the stage for a successful boot, and it’s a step you absolutely don't want to skip.

2. Checking BIOS/UEFI Boot Order

Okay, you've made sure GRUB is installed correctly, but your system still isn't booting. Let's head into the BIOS or UEFI settings – this is where your computer decides what to boot from. The BIOS/UEFI boot order is essentially a list of devices your computer checks when it starts up. If your RAID array isn't on this list, or if it's lower down the list than other devices, your system might skip it and try to boot from something else. Accessing the BIOS/UEFI settings usually involves pressing a key (like Delete, F2, F12, or Esc) during startup – the specific key varies depending on your motherboard manufacturer, so keep an eye on the screen during boot for the prompt. Once you're in the BIOS/UEFI setup, navigate to the boot order settings. Look for a list of bootable devices. Your RAID array should be listed here, often identified by its mdadm device name (like /dev/md0) or the individual disks in the array. Make sure your RAID array is at the top of the list or at least higher than any other potential boot devices (like USB drives or other hard drives). Some BIOS/UEFI systems might have specific settings related to RAID or SATA modes. Ensure that these settings are correctly configured for your RAID setup. For example, you might need to set the SATA mode to RAID instead of AHCI. After making changes, save your settings and exit the BIOS/UEFI setup. Your system should now try booting from your RAID array first. This simple check can often resolve boot issues, so it's a step well worth taking. If your RAID is not on the list, you will need to make sure the RAID is properly configured and detected by the BIOS/UEFI.

3. Ensuring RAID Drivers in Initramfs

So, you've checked the bootloader and the BIOS settings, and everything seems right, but your AlmaLinux system still refuses to boot. Let's dive into the initramfs, a critical component for booting from a RAID array. Think of initramfs as a mini-environment that loads before your main operating system. It contains essential drivers and utilities needed to mount your root file system. If the drivers for your RAID controller aren't included in the initramfs, your system won't be able to recognize the RAID array during boot, and you'll be stuck with that frustrating "No bootable devices" message. To fix this, you need to ensure that the necessary RAID drivers are included in the initramfs. This usually involves using a tool like dracut, which is common in AlmaLinux and other Red Hat-based distributions. First, you'll need to boot into a rescue environment, just like when we were checking the bootloader. Mount your root partition so you can access your system files. Then, you can use the dracut command to regenerate the initramfs. A common command is `dracut -f --add-drivers=