Sunil Venkatesh CMSC601 Spring 2011 05022011 Introduction Linux OS Supports more than 30 filesystems VFS subsystem Data structures inode file vmareastruct dentry and superblock ID: 329226
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Slide1
Layered File System
Sunil Venkatesh
CMSC-601, Spring 2011, 05-02-2011Slide2
Introduction
Linux OS
Supports more than 30 filesystems
VFS subsystemData structures – inode, file, vm_area_struct, dentry and super_block
User Application
VFS Layer
Filesystem
Sys-call interface
Conceptual (VFS interface)
Physical Media
User
KernelSlide3
Motivation
Challenges in administering a Linux server
Users, Groups and Others (RWX)
Maintaining softwareNew featuresDelegation of authoritySecurity through isolation (“chroot jail”)Benefits in a CloudData is secureEasier maintenance of web- servicesSlide4
Related Work
Hendricks et al., Method and apparatus for translucent file system, 1991
Works best when a team working on shared data
Shared and Private hierarchyErez Zadok and Ion Badulescu, A Stackable File System Interface For Linuxvnode – represents files, directories and devices.
wrapfs achieved through vnode interfaceErez
Zadok and Ion Badulescu and Alex Shender, Cryptfs: A Stackable Vnode Level Encryption File System, 1998. Slide5
Depicting Layers
System Layer
Active Kernels
2.6.18-128.el5
2.6.38.4
Inactive Kernels
2.6.39-rc5
Layer Contents:
vmlinuz
initrd
grub
Application Layer
Graphics
Toosl
OpenGL
Glib
DirectFB
Development Tools
gcc
Java
fortron
Office Tools
word
spreadsheet
User Layer
User Group 1
alpha
bravo
charlie
User Group 2
delta
echo
foxtrot
User Group 3
golf
hotel
These layers in-turn can contain
sublayers
like: dev, testSlide6
Layered Organization
prj1
prj2
. . . . . . .
prj3
temp
. . . . . . .
base
prj
N
test
dev
test
dev
test
dev
test
bin
. . . . . . .
home
mnt
usr
/
bash
mkdir
mount
netstat
ping
pwd
tracepath
traceroute
…
unmount
bin
lib
sbin
share
. . . . . . .
Legend:
White Font: Directory
Black Font: File
T1M1 – Team 1, Member 1
dev
lib
root
bin
. . . . . . .
home
mnt
usr
/
bash
mkdir
mount
netstat
ping
pwd
tracepath
traceroute
…
unmount
bin
lib
sbin
share
. . . . . . .
Legend:
White Font: Directory
Black Font: File
T1M1 – Team 1, Member 1
dev
lib
root
T1M1
T1M2
T1M3
T1MN
. . . . . . .
bin
. . . . . . .
home
mnt
usr
/
bash
mkdir
mount
netstat
ping
pwd
tracepath
traceroute
…
unmount
bin
lib
sbin
share
. . . . . . .
Legend:
White Font: Directory
Black Font: File
T1M1 – Team 1, Member 1
dev
lib
root
T2M1
T2M2
T2M3
T2MN
. . . . . . .
bin
. . . . . . .
home
mnt
usr
/
bash
mkdir
mount
netstat
ping
pwd
tracepath
traceroute
…
unmount
bin
lib
sbin
share
. . . . . . .
Legend:
White Font: Directory
Black Font: File
T1M1 – Team 1, Member 1
dev
lib
root
TNM1
T NM2
TNM3
TNMN
. . . . . . .
dev
Level 1
Level 2
Level 3Slide7
An Example of a Layer
bin
. . . . . . .
home
mnt
usr
/
bash
mkdir
mount
netstat
ping
pwd
tracepath
traceroute
…
unmount
bin
lib
sbin
share
. . . . . . .
Legend:
White Font: Directory
Black Font: File
T1M1 – Team 1, Member 1
dev
lib
root
T1M1
T1M2
T1M3
T1MN
. . . . . . .
Python (v2.3)
gcc (v3.4)
Test Code 1
Test Code 2
Test Code 1
Test Code 1
Level 2
Level 3Slide8
Implementation
User Application
VFS Layer
Filesystem
Sys-call interface
Conceptual (VFS interface)
Physical Media
User
Kernel
wrapfs
Components to be implemented
A pseudo-filesystem
wrapfs layer
Modification
dentry operationsSlide9
Future Work
Layered hierarchy representation
Provide means for delegation of authority
Eliminate need for a user and group permission in each fileSlide10
Questions/Suggestions