Linux File SystemsPresented by: Lloyd Brown, James Frazee, & Travis Wertz

File System Capabilities

File types Permissions

File Types

Regular Files Directories Links

Symbolic Hard

Permissions

Old Unix-style Standard Permissions: Universal User, Group, Others Example:

user@host~$ ls -lh procmail.log-rw------- 1 lbrown lbrown 47K Mar 30

14:17 procmail.log

Permissions Access Control List (ACL)

Allows arbitrary users/groups to be given permissions to files

Example:user@host# getfacl www# file: www# owner: root# group: clusterstatuser::rwxuser:36:r-xgroup::rwxgroup:clusterstat:rwxgroup:clusterstat_ro:r-xmask::rwxother::---default:user::rwxdefault:user:36:r-xdefault:group::rwxdefault:group:clusterstat:rwxdefault:group:clusterstat_ro:r-xdefault:mask::rwxdefault:other::---

Virtual File Systems

Inodes Dentrys Superblocks

Inode

I(ndex)Node Describes location of each file,

directory, or link within every FS Identified by a tuple containing

unique number

Dentry

Directory Entry Used to map file descriptors to

inodes Contains name of file or directory File descriptor points to a dentry,

which points to inode.

Dentry Example

/home/chris /home/jim

/home

/home/chris/foo /home/chris/bar /home/chris/txt

Dentry

Pointer

Superblock

When FS is mounted, contents are attached to primary directory tree

Superblock contains information about mounted FS Type Root inode location Items that protect integrity

Created by kernel Resides in memory

Specific Types

General File Systems Network File Systems Special Purpose File Systems

General File Systems

Ext 2/3 ReiserFS JFS XFS

Network File Systems

NFS SMB/CIFS

Memory File Systems

ProcFS TmpFS SysFS RamFS