Книга: Fedora™ Unleashed, 2008 edition

Examine an initrd Image File

Examine an initrd Image File

The initrd.img file is automatically created during the installation process (if necessary) or with the mkinitrd command. You never need to examine it, but if you are curious about what's in the initrd.img file, just take a look: It is really just a gzipped ext2 file system. To examine it, first copy it to the /tmp directory and add the .gz suffix to it:

# cp /boot/initrd-2.6.7-1.478.img /tmp/initrd-2.6.7-1.478.img.gz

If your system does not have an initrd.img file in /boot, mount your boot floppy and see whether it has one. Next, uncompress it as follows:

# gunzip /tmp/initrd-2.6.7-1.478.img.gz

Mount it as follows:

# mount -o loop /tmp/initrd-2.6.7-1.478.img /mnt/image

and browse the directory to your heart's content.

Not every system has an initrd.img file. It is typically used to load device drivers for file systems (such as Reiser) or hardware (such as the Promise RAID IDE controller) that must be in place before the system can continue booting. Some floppy-disc-based Linux distributions use initrd.img to load a minimal operating system that can then uncompress and load the working file system from the floppy.

You can also mount .iso images in the same way, but remember that they are always read-only because of the nature of the underlying iso9660 file system; you can write to the other images unless you explicitly mount them as read-only. If you want to read and write to the files in an ISO file system, you must first copy the files to a device that is mounted read-write, make your changes, and then use mkisofs to create a new .iso image. This is a common "gotcha" for many users.

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