Initramfs init
mkinitfs is a tool to create initramfs images. Initramfs images are small images which contain a small filesystem with everything required to boot Alpine. For example, when booting a setup with full disk encryption, the initramfs contains the binaries required to prompt for a password and mount the encrypted disk.
Usage
Under a running alpine machine, the following command can be used if for some reason the initramfs has not been created properly for a new kernel.
# mkinitfs -c /etc/mkinitfs/mkinitfs.conf -b / <kernelvers>
The script is located in /sbin/ and is created with ash. It expects /lib/modules to be populated with the <kernelvers> listed.
Therefore normally just running mkinitfs should be enough if you need to rebuild it.
Sometimes, e.g. to fix a non booting installation or when installing, you may have to rebuild the initramfs from another system, you do not need to chroot.
Mount /, /boot etc. and then run:
# mkinitfs -c /mnt/etc/mkinitfs/mkinitfs.conf -b /mnt/ $(ls /mnt/lib/modules/)
Initramfs init cmdline options
In addition to the kernel boot parameters are a number of parameters that the init script understands. These are documented in the mkinitfs-bootparam(7) man page.
Depending on your HDD type and filesystem used, the file appears as follows:
Contents of /etc/mkinitfs/mkinitfs.conf
Although you may specify your own init script when building an initramfs, these parameters allow for extensive control over the initial startup of an Alpine Linux system.
Troubleshooting
To troubleshoot booting issues, when using grub, replace quiet with debug_init single in the boot command line.