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How do I have Linux boot with rootfs in RAM?
Normally, the bootloader extracts the compressed kernel from the flash into the SDRAM, and then kernel mounts /dev/mtdblock2 as the rootfs. I am trying to improve the bootloader so it can download an image to its RAM and boot without writing to the flash.
How to build an uncompressed root filesystem in Windows?
Creating the root filesystem involves selecting files necessary for the system to run. In this section we describe how to build a compressed root filesystem. A less common option is to build an uncompressed filesystem on a diskette that is directly mounted as root; this alternative is described in Section 9.1. 4.1. Overview
Is there a way to boot from the Flash?
Squashfs support is built-in and it already works with for booting from the flash. EDIT: This is a MIPS based embedded device, using a custom bootloader. Normally, the bootloader extracts the compressed kernel from the flash into the SDRAM, and then kernel mounts /dev/mtdblock2 as the rootfs.
Can you run fsck on a root drive?
Then you can run fsck on your original root drive while it is not mounted. Restore all or part of your original root drive from backup using archive and compression utilities such as cpio , tar, gzip and ftape .
What does rootfs do in the Linux kernel?
After extracting, the kernel checks to see if rootfs contains a file “init”, and if so it executes it as PID 1. If found, this init process is responsible for bringing the system the rest of the way up, including locating and mounting the real root device (if any).
How to force rootfs to use ramfs instead of ramfs?
If CONFIG_TMPFS is enabled, rootfs will use tmpfs instead of ramfs by default. To force ramfs, add “rootfstype=ramfs” to the kernel command line. All 2.6 Linux kernels contain a gzipped “cpio” format archive, which is extracted into rootfs when the kernel boots up.
What happens if rootfs does not contain an init program?
If rootfs does not contain an init program after the embedded cpio archive is extracted into it, the kernel will fall through to the older code to locate and mount a root partition, then exec some variant of /sbin/init out of that. All this differs from the old initrd in several ways:
Which is the root filesystem in Linux 2.4?
Instead, the initramfs is unpacked in a special ramfs-based filesystem called the rootfs. The ramfs filesystem support is built into the kernel and cannot be disabled, so it’s always available. Because it doesn’t use backing store, it’s a simpler system than the mechanism used in the 2.4 kernel.
Is the initramfs file embedded in the kernel?
The initramfs file is always embedded in the kernel (for all hardware platforms) even if you don’t create one yourself. If you don’t, a default CPIO archive is created automatically by the kernel build process. Second, there is no external filesystem required at boot time for the initramfs.
How to run a shell in embedded Linux?
The first method is to use a file specified at boot time with the init= kernel parameter. If this parameter is not set, the kernel tries a series of locations to find a file named “init”. These include /sbin/init, /etc/init, and /bin/init. If all these fail, the kernel tries to run any shell it finds at /bin/sh.