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Rebuilding the Linux ramdisk
A New Beginning
After moving your hard disk to a new system, the Linux system suddenly fails to boot. Often this happens because of missing drivers in the ramdisk, which the kernel needs to boot the system. In this article, I take a closer look at the handling of the initramfs file and introduces dracut [1] as a practical helper.
Many users only see the initramfs (initial random access memory filesystem) archive file as yet another file in the boot directory. It is automatically created when a new kernel is installed and deleted again when the kernel is removed from the system. But this initial ramdisk plays an important role, since it ensures that the root filesystem can be accessed after the computer has been restarted, to be able to access all the tools that are necessary for the computer to continue booting.
The GRUB2 bootloader, used in most cases today, is responsible for loading the Linux kernel (vmlinuz) and a ramdisk (initramfs) into memory at boot time. The kernel then mounts the ramdisk on the system as a root volume and then starts the actual init process. On current Linux systems, this is typically systemd. The init process can then use the drivers and programs provided by initramfs to gain access to the root volume itself. The root volume is usually available on a local block device but can also be mounted over the network, if required. For this to work, all the required drivers must, of course, be available in the initramfs.
These can be drivers for LVM, RAID, the filesystem, the network, or a variety of other components. The details of this depend on the individual configuration of the system. For example, if the root filesystem is located on an encrypted partition, the tools for accessing it must be available within the ramdisk.
When installing a new kernel,
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