The “Virtual File System” in Linux
My discussion is now finished, but there are many places where interesting source code is available for viewing. Implementations of file system types worth examining:
Obviously, the “/proc” file system: it is quite easy to look at, because it is neither performance-critical nor particularly fully featured (except the sysctl idea). Enough said.
The “UMSDOS” file system: it is part of the mainstream kernel and runs piggy-back on the “Ms-DOS” file system. It implements only a few of the operations of the VFS to add new capabilities to an old-fashioned file system format.
The “userfs” module: it is available from both tsx-11 and sunsite under ALPHA/userfs; version 0.9.3 will load to Linux 2.0. This module defines a new file system type which uses external programs to retrieve data; interesting applications are the ftp file system and a read-only file system to mount compressed tar files. Even though reverting to user programs to get file system data is dangerous and might lead to unexpected deadlocks, the idea is quite interesting.
“supermount”: the file system is available on sunsite and mirrors. This file system type is able to mount removable devices like floppies or CD-ROMs and handle device removal without forcing the user to umount/mount the device. The module works by controlling another file system type while arranging to keep the device unmounted when it is not used; the operation is transparent to the user.
“ext2”: the extended-2 file system has been the standard Linux file system for a few years now. It is difficult code, but worth reading for those interested in seeing how a real file system is implemented. It also has hooks for interesting security features like the immutable-flag and the append-only-flag. Files marked as immutable or append-only can only be deleted when the system is in single-user mode, and are therefore secured from network intruders.
“romfs”: this is the smallest file system I've ever seen. It was introduced in Linux-2.1.21. It's a single source file, and it's quite enjoyable to browse. As its name asserts, it is read-only.
is a wild soul with an attraction for source code. He is a fan of Linus Torvalds and Baden Powell and enjoys the two communities of volunteer workers they have attracted. He can be reached at firstname.lastname@example.org.
|Graph Any Data with Cacti!||Apr 27, 2017|
|Be Kind, Buffer!||Apr 26, 2017|
|Preparing Data for Machine Learning||Apr 25, 2017|
|openHAB||Apr 24, 2017|
|Omesh Tickoo and Ravi Iyer's Making Sense of Sensors (Apress)||Apr 21, 2017|
|Low Power Wireless: 6LoWPAN, IEEE802.15.4 and the Raspberry Pi||Apr 20, 2017|
- Graph Any Data with Cacti!
- Teradici's Cloud Access Platform: "Plug & Play" Cloud for the Enterprise
- The Weather Outside Is Frightful (Or Is It?)
- Simple Server Hardening
- Understanding Firewalld in Multi-Zone Configurations
- Gordon H. Williams' Making Things Smart (Maker Media, Inc.)
- From vs. to + for Microsoft and Linux
- Server Technology's HDOT Alt-Phase Switched POPS PDU
- IGEL Universal Desktop Converter
Pick up any e-commerce web or mobile app today, and you’ll be holding a mashup of interconnected applications and services from a variety of different providers. For instance, when you connect to Amazon’s e-commerce app, cookies, tags and pixels that are monitored by solutions like Exact Target, BazaarVoice, Bing, Shopzilla, Liveramp and Google Tag Manager track every action you take. You’re presented with special offers and coupons based on your viewing and buying patterns. If you find something you want for your birthday, a third party manages your wish list, which you can share through multiple social- media outlets or email to a friend. When you select something to buy, you find yourself presented with similar items as kind suggestions. And when you finally check out, you’re offered the ability to pay with promo codes, gifts cards, PayPal or a variety of credit cards.Get the Guide