index nodes, i-nodes

data blocks

superblock

Part

itio

n

/

a cb

bin dev homevar

d

Partition

dir1

dir2 dir3 dir4

Filesystem Basics

mounting

hardlink

mount

umount

LINKDifferent identity for the same file

Hard links cannot be created between filesystems

Hard link Soft link (symbolic)

Advantages make data available in multiple places without duplication give multiple names to the same command

ln [options] target [link]

-s, --symbolic

-f, --force

-I, --interactive

Managing Links

Linux file security is build upon: file ownership file permissions

ownership(two tiered)

permissions(three tiered)

owner group

owner group others

Files can be owned by non-login accountsUser and Group are represented internally by numbers

chown [options] [newowner][:newgroup] filename

chgrp [options] newgroup filename

can only be run by root

File Ownership

- r w x r x r - x

owner permissions

group permissions

others (world) permissionsfile type code

r read 4w write 2x execute 1

SUID

SGID

Sticky bit

s in owner execute bit

s in group execute bit

t in world execute bit

Symlinks always have 777 permissions.

Changing the permissions on a symlink affects the targeted file.

File Permissions

chmod [options] [mode[,mode]] filename

mode

octal number NNNN

symbolic form =

ugoa

+-=

rwxXstugo

Permissions can only be adjusted by owner and root.Set Default Mode:

umask

Mask is subtracted from 0666 for files and

0777 for directories.

Changing Permissions

chattr attr file

-

+

=

Attributes:a - append only

i - immutable

s - secure deletion

t - no tail merge

A - no access time updates

j - journal (not on ext2)

File Attributes

quotas require support in the kernel

in the filesystem

mount options in /etc/fstab:

usrquota grpquota

edquota

edquota -t set grace periodquotacheck on a filesystem basis

Disk Quotas

Filesystem Hierarchy Standard (FHS)

static

variable

shareable unshareable

/usr/opt

/etc/boot

/home/var/mail

/var/run/var/lock

find [path] [expression]

locate

whereis

whichSearches environment path for the first occurrence of the program

Searches for binary, configuration and documentation of a program

Locating Files