the previous article) to understand the details of partitioning. partition.c and partition.h provide the functionality to emulate the various partition tables on the disk on RAM. ram_device.c and ram_device.h abstract the underlying RAM operations like vmalloc/ vfree, memcpy, etc, providing disk operation APIs like init/ cleanup, read/ write, etc. c files represent a specific part of the driver. So, let’s dig into the nitty-gritties to decode the rules. We have just now played around with the disk on RAM but without actually knowing the rules, i.e.

Please note that all the above experimenting steps need to be executed with root privileges.įigure 27: Formatting the third partition (/dev/rb3) Now, let’s learn the rules Though the partition needs to be unmounted using ‘ umount /mnt‘ before doing that. Unloading the driver using ‘ rmmod dor‘ would vanish everything.But, please remember that these partitions are all on a disk on RAM, and so non-persistent. You may go ahead and store your files there. Disk usage utility df would now show this partition mounted at /mnt (Figure 27).

Mount the newly formatted partition using mount, say at /mnt (Figure 27).

(Quick) Format the third primary partition ( /dev/rb3) as vfat filesystem (like your pen drive), using mkfs.vfat (Figure 27).

Display the partition info for the disk using fdisk.

Display the initial contents of the first partition ( /dev/rb1) using the xxd utility.

Write some text into the disk’s first partition ( /dev/rb1) using cat.

Zero out the first sector of the disk’s first partition ( /dev/rb1) again using dd.

Read the entire disk ( /dev/rb) using the disk dump utility dd.

rb1, rb2, rb3 are the primary partitions with rb2 being the extended partition and containing the 3 logical partitions rb5, rb6, rb7. dev/rb is the entire disk of 512 KiB size.

Checkout the automatically created block device files ( /dev/rb*).

This would create the block device files representing the disk on 512 KibiBytes (KiB) of RAM, with 3 primary and 3 logical partitions. Once built, the following are the experimenting steps (Refer to Figures 25, 26, 27): make clean would do the usual clean of the built stuff. As usual, executing make will build the ‘disk on ram’ driver ( dor.ko) – this time combining the 3 ‘C’ files. This tar ball contains 3 ‘C’ source files, 2 ‘C’ headers, and a Makefile. << Fourteenth Article Play first, rules laterĪfter a delicious lunch, theory makes audience sleepy. This fifteenth article, which is part of the series on Linux device drivers, experiments with a dummy hard disk on RAM to demonstrate the block drivers.

Gendisk Drivers