A- How are organized files in Linux ?
If we examine the root file system of a typical linux fedora system, the Linux file system uses the command "ls" for showing file content . Running it as root, we get the following results :
root@localhost /# ls
bin dev home lib64 media opt run srv tmp var
boot etc lib lost+found mnt proc root sbin sys usr
The file system is organized in sections :
/bin Essential user command binaries (for use by all users)
/boot Static files of the boot loader, only used at system startup
/dev Device files, links to your hardware devices like /dev/sound, /dev/input
/etc Host-specific system configuration
/home User home directories. This is where you save your personal files
/lib Essential shared libraries and kernel modules
/mnt Mount point for a temporarily mounted filesystem like /mnt/cdrom
/opt Add-on application software packages
/usr /usr is the second major section of the filesystem. /usr is shareable, read-only data.
/var contains variable data files. This includes spool directories and files, administrative and logging data, and transient and temporary files.
/proc System information stored in memory mirrored as file
1. INODES
in order to show the inodes associated with the files, we must use the -i option : the inodes are associated registries associated with each file containing some metadatas. Inodes stands for Index Nodes. There is an inode number for each file. For example inode=5829 for the directory bin. In POSIX and partially POSIX-compliant operating systems, such as GNU/Linux, Android, Apple's Mac OS X, Windows NT operating systems, an inode contains information about :
- the size of the file in bytes, in blocks and IO blocks
- the devicesID, inodeID, Links (how many hard links are pointing to the inode, an hard link) and timestamps last accessed last modified for each UID UserID and GID Group ID. The
stat system call retrieves a file's inode number and some of the information in the inode.root@localhost /# ls -i
5829 bin 17 lib 1835009 opt 13 sbin 786433 var
2 boot 16 lib64 1 proc 1179649 srv
1025 dev 11 lost+found 3267 q 1 sys
1310721 etc 1966081 media 1703937 root 8070 tmp
2 home 1048577 mnt 1159 run 2883585 usr
root@localhost /# stat boot
File: ‘boot’
Size: 1024 Blocks: 4 IO Block: 1024 directory
Device: 801h/2049d Inode: 2 Links: 4
Access: (0555/dr-xr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2014-05-11 15:39:55.000000000 +0200
Modify: 2014-01-09 03:12:33.000000000 +0100
Change: 2014-01-09 03:12:33.000000000 +0100
Birth: -
1. ACCESS RIGHTS
in order to show the access rights, ls must be used with -lroot@localhost /# ls -l /etc
total 2936
drwxr-xr-x. 3 root root 4096 25. Aug 2013 abrt
-rw-r--r-- 1 root root 47 16. Mär 21:15 adjtime
drwxr-xr-x 2 root root 4096 7. Okt 2013 akonadi
-rw-r--r--. 1 root root 1518 7. Jun 2013 aliases
-rw-r-----. 1 root smmsp 12288 19. Aug 2013 aliases.db
drwxr-xr-x. 2 root root 4096 25. Aug 2013 alsa
drwxr-xr-x. 2 root root 4096 16. Apr 23:07 alternatives
...
system_u:object_r:bin_t:s0 bin -> usr/bin
system_u:object_r:boot_t:s0 boot
? dev
system_u:object_r:etc_t:s0 etc
system_u:object_r:home_root_t:s0 home
system_u:object_r:lib_t:s0 lib -> usr/lib
system_u:object_r:lib_t:s0 lib64 -> usr/lib64
...
NAME
ls - list directory contents
SYNOPSIS
ls [OPTION]... [FILE]...
DESCRIPTION
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is speci‐
fied.
Mandatory arguments to long options are mandatory for short options
too.
-a, --all
do not ignore entries starting with .
-A, --almost-all
do not list implied . and ..
--author
with -l, print the author of each file
-b, --escape
print C-style escapes for nongraphic characters
--block-size=SIZE
scale sizes by SIZE before printing them. E.g.,
'--block-size=M' prints sizes in units of 1,048,576 bytes. See
SIZE format below.
-B, --ignore-backups
do not list implied entries ending with ~
-c with -lt: sort by, and show, ctime (time of last modification of
file status information) with -l: show ctime and sort by name
otherwise: sort by ctime, newest first
-C list entries by columns
--color[=WHEN]
colorize the output. WHEN defaults to 'always' or can be
'never' or 'auto'. More info below
-d, --directory
list directory entries instead of contents, and do not derefer‐
ence symbolic links
-D, --dired
generate output designed for Emacs' dired mode
-f do not sort, enable -aU, disable -ls --color
-F, --classify
append indicator (one of */=>@|) to entries
--file-type
likewise, except do not append '*'
--format=WORD
across -x, commas -m, horizontal -x, long -l, single-column -1,
verbose -l, vertical -C
--full-time
like -l --time-style=full-iso
-g like -l, but do not list owner
--group-directories-first
group directories before files.
augment with a --sort option, but any use of --sort=none (-U)
disables grouping
-G, --no-group
in a long listing, don't print group names
-h, --human-readable
with -l, print sizes in human readable format (e.g., 1K 234M 2G)
--si likewise, but use powers of 1000 not 1024
-H, --dereference-command-line
follow symbolic links listed on the command line
--dereference-command-line-symlink-to-dir
follow each command line symbolic link that points to a direc‐
tory
--hide=PATTERN
do not list implied entries matching shell PATTERN (overridden
by -a or -A)
--indicator-style=WORD
append indicator with style WORD to entry names: none (default),
slash (-p), file-type (--file-type), classify (-F)
-i, --inode
print the index number of each file
-I, --ignore=PATTERN
do not list implied entries matching shell PATTERN
-k, --kibibytes
use 1024-byte blocks
-l use a long listing format
-L, --dereference
when showing file information for a symbolic link, show informa‐
tion for the file the link references rather than for the link
itself
-m fill width with a comma separated list of entries
-n, --numeric-uid-gid
like -l, but list numeric user and group IDs
-N, --literal
print raw entry names (don't treat e.g. control characters spe‐
cially)
-o like -l, but do not list group information
-p, --indicator-style=slash
append / indicator to directories
-q, --hide-control-chars
print ? instead of non graphic characters
--show-control-chars
show non graphic characters as-is (default unless program is
'ls' and output is a terminal)
-Q, --quote-name
enclose entry names in double quotes
--quoting-style=WORD
use quoting style WORD for entry names: literal, locale, shell,
shell-always, c, escape
-r, --reverse
reverse order while sorting
-R, --recursive
list subdirectories recursively
-s, --size
print the allocated size of each file, in blocks
-S sort by file size
--sort=WORD
sort by WORD instead of name: none -U, extension -X, size -S,
time -t, version -v
--time=WORD
with -l, show time as WORD instead of modification time: atime
-u, access -u, use -u, ctime -c, or status -c; use specified
time as sort key if --sort=time
--time-style=STYLE
with -l, show times using style STYLE: full-iso, long-iso, iso,
locale, +FORMAT. FORMAT is interpreted like 'date'; if FORMAT
is FORMAT1<newline>FORMAT2, FORMAT1 applies to non-recent files
and FORMAT2 to recent files; if STYLE is prefixed with 'posix-',
STYLE takes effect only outside the POSIX locale
-t sort by modification time, newest first
-T, --tabsize=COLS
assume tab stops at each COLS instead of 8
-u with -lt: sort by, and show, access time with -l: show access
time and sort by name otherwise: sort by access time
-U do not sort; list entries in directory order
-v natural sort of (version) numbers within text
-w, --width=COLS
assume screen width instead of current value
-x list entries by lines instead of by columns
-X sort alphabetically by entry extension
-1 list one file per line
SELinux options:
--lcontext
Display security context. Enable -l. Lines will probably be
too wide for most displays.
-Z, --context
Display security context so it fits on most displays. Displays
only mode, user, group, security context and file name.
--scontext
Display only security context and file name.
--help display this help and exit
--version
output version information and exit
SIZE is an integer and optional unit (example: 10M is 10*1024*1024).
Units are K, M, G, T, P, E, Z, Y (powers of 1024) or KB, MB, ... (pow‐
ers of 1000).
Using color to distinguish file types is disabled both by default and
with --color=never. With --color=auto, ls emits color codes only when
standard output is connected to a terminal. The LS_COLORS environment
variable can change the settings. Use the dircolors command to set it.
Exit status:
0 if OK,
1 if minor problems (e.g., cannot access subdirectory),
2 if serious trouble (e.g., cannot access command-line argument).
AUTHORS
Written by Richard M. Stallman and David MacKenzie.
