L AYERED F ILE S YSTEM Sunil Venkatesh CMSC-601, Spring 2011, 05-02-2011.
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LAYERED FILE SYSTEM Sunil Venkatesh CMSC-601, Spring 2011, 05-02-2011
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Transcript of L AYERED F ILE S YSTEM Sunil Venkatesh CMSC-601, Spring 2011, 05-02-2011.
LAYERED FILE SYSTEMSunil Venkatesh
CMSC-601, Spring 2011, 05-02-2011
INTRODUCTION
Linux OS Supports more than 30 filesystems VFS subsystem
Data structures – inode, file,vm_area_struct, dentry and super_block
User Application
VFS Layer
Filesystem
Sys-call interface
Conceptual (VFS interface)
Physical Media
User
Kernel
MOTIVATION
Challenges in administering a Linux server Users, Groups and Others (RWX) Maintaining software
New features Delegation of authority Security through isolation (“chroot jail”)
Benefits in a Cloud Data is secure Easier maintenance of web- services
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 hierarchy
Erez Zadok and Ion Badulescu, A Stackable File System Interface For Linux vnode – represents files, directories and devices. wrapfs achieved through vnode interface
Erez Zadok and Ion Badulescu and Alex Shender, Cryptfs: A Stackable Vnode Level Encryption File System, 1998.
DEPICTING LAYERSSystem Layer
Active Kernels
2.6.18-128.el5 2.6.38.4
Inactive Kernels
2.6.39-rc5
Layer Contents:
vmlinuzinitrdgrub
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, test
LAYERED ORGANIZATION
prj1 prj2. . . . . . . prj3 temp. . . . . . .
base
prjN
test
dev
test
dev
test
dev
test
bin . . . . . . . home mnt usr
/
bashmkdirmountnetstat
pingpwd
tracepathtraceroute
…unmount
bin lib sbin share. . . . . . .
Legend:White Font: DirectoryBlack Font: File
T1M1 – Team 1, Member 1
dev lib root
bin . . . . . . . home mnt usr
/
bashmkdirmountnetstat
pingpwd
tracepathtraceroute
…unmount
bin lib sbin share. . . . . . .
Legend:White Font: DirectoryBlack Font: File
T1M1 – Team 1, Member 1
dev lib root
T1M1 T1M2 T1M3 T1MN. . . . . . .
bin . . . . . . . home mnt usr
/
bashmkdirmountnetstat
pingpwd
tracepathtraceroute
…unmount
bin lib sbin share. . . . . . .
Legend:White Font: DirectoryBlack Font: File
T1M1 – Team 1, Member 1
dev lib root
T2M1 T2M2 T2M3 T2MN. . . . . . .
bin . . . . . . . home mnt usr
/
bashmkdirmountnetstat
pingpwd
tracepathtraceroute
…unmount
bin lib sbin share. . . . . . .
Legend:White Font: DirectoryBlack Font: File
T1M1 – Team 1, Member 1
dev lib root
TNM1 T NM2 TNM3 TNMN. . . . . . .
dev
Level 1
Level 2
Level 3
AN EXAMPLE OF A LAYER
bin . . . . . . . home mnt usr
/
bashmkdirmountnetstat
pingpwd
tracepathtraceroute
…unmount
bin lib sbin share. . . . . . .
Legend:White Font: DirectoryBlack 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 2Test Code 1 Test Code 1
Level 2
Level 3
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 operations
FUTURE WORK
Layered hierarchy representation Provide means for delegation of authority Eliminate need for a user and group
permission in each file
QUESTIONS/SUGGESTIONS
