memdiskfind

locate a MEMDISK instance in memory

TLDR

Find MEMDISK and print parameters for phram

$ memdiskfind

Load MEMDISK image via phram

$ modprobe phram phram=memdisk,$(memdiskfind)

Expose MEMDISK image as a block device

$ modprobe mtdblock

memdiskfind searches physical memory for a MEMDISK instance (a disk image loaded by SYSLINUX's MEMDISK boot loader) and, if found, prints the address and length of the image in a format understood by the Linux phram (physical-memory-as-MTD) driver.Typical usage is inside an initramfs: once memdiskfind locates the image, phram exposes it as an MTD device and mtdblock turns that into a /dev/mtdblock0 block device that can be mounted (for example, an ISO image booted via MEMDISK).memdiskfind is part of the syslinux-utils package. It can also be compiled with klibc to produce a smaller static binary suitable for initramfs images.

OUTPUT

The output is a single line of the form address,size (both in hex, with 0x prefix) suitable for passing directly to `modprobe phram`.

INSTALL

sudo apt install syslinux-utils

sudo dnf install syslinux

sudo pacman -S syslinux

sudo apk add syslinux

sudo zypper install syslinux

nix profile install nixpkgs#syslinux

CAVEATS

Requires that the system was booted via MEMDISK. Must typically run as root to read /proc/iomem or scan physical memory. Intended for use before the root filesystem is mounted, i.e. from an initramfs.

HISTORY

memdiskfind is part of the SYSLINUX project's utilities, created by H. Peter Anvin and contributors to aid booting of ISO/floppy images loaded into memory by MEMDISK.