What is Rootfs Cpio?

What is Rootfs Cpio?

So how does it work? (Rootfs and cpio.) This is a special instance of tmpfs which can’t be moved or unmounted. [1] Most 2.6 systems just leave it empty and mount another root filesystem on top of it, but rootfs is always there (check /proc/mounts to see) and it’s a fully capable ram based filesystem.

How do I mount a RAM disk image in Linux?

Modifying the root filesystem

1. Extract the initrd image from the gzip archive. gunzip ramdisk.image.gz.
2. Mount the initrd image. chmod u+rwx ramdisk.image. mkdir tmp_mnt/ sudo mount -o loop ramdisk.image tmp_mnt/ cd tmp_mnt/
3. Make changes in the mounted filesystem.
4. Unmount the initrd image and compress the image.

How do I find the root file in Linux?

If you use the mount command in Linux, you can see that the root device is not listed like the other mounted filesystems: /dev/root on / type ext3 (rw) /dev/mmcblk0p1 on /mmcboot type vfat (rw) proc on /proc type proc (rw) none on /sys type sysfs (rw,noexec,nosuid,nodev) none on /dev type tmpfs (rw,mode=0755) …

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 does the Linux kernel extract into rootfs?

All 2.6 Linux kernels contain a gzipped “cpio” format archive, which is extracted into rootfs when the kernel boots up. After extracting, the kernel checks to see if rootfs contains a file “init”, and if so it executes it as PID 1.

Do you need root access to initramfs file?

Run “usr/gen_init_cpio” (after the kernel build) to get a usage message documenting the above file format. One advantage of the configuration file is that root access is not required to set permissions or create device nodes in the new archive.

Where to find initramfs file in Linux kernel?

(Note that those two example “file” entries expect to find files named “init.sh” and “busybox” in a directory called “initramfs”, under the linux-2.6.* directory. See Early userspace support for more details.) The kernel does not depend on external cpio tools.