File system
using 'ls -l' command to get details
Ex.
-rw-r--r-- 1 xatierlike xatierlike 1631 2011-09-14 02:16 class1
file type
file access mode # rwx for read, write, execute
numbers of inodes
file user owner
filegroup owner
file size
file last modify time
file name
file system achitecture
pathname
file tree
mounting
file type
inode and file
link
'ln' command
file access mode
changing file owner
freebsd bonus flags # to protect your important files
file system architecture
system call
Application <=========> kernel <=> hardware
process1, process2, process3.... [user mode]
-----------------------------------------------------
virtual file system [system mode]
|
device drivers ---> devices
purpose of file system
represent and organize the system's storage
namespace
API
security model
implementation
system call via APIs
OS will do the detail jobs
relationship of API, system call, OS
+-- user appication ---
user APIs | ^
mode V |
------------------- system call interface ---------------------
kernel | |
mode +---> do some magic -+
objects in the filesystems
files and directories
hardware device files (under /dev/... )
processes information
Interprocess communication (IPC)
shared memory segments (SHM)
we can uer filesystem interface to access such objects
Ex. open, read, write, close, seek ... etc.
pathname
where it is?
absolute path => start from /
relative path => start from your current directory
contrains of pathname
single componetn <= 255 char
single absolute path <= 1024 char
file tree
the data struct of files in your system
/ (root)
some important directories under root
/bin & /sbin user utilities and system programs
/dev device
/etc system configurations and scripts
/home where you live
/mnt for system admins to mount something
/proc images and running process
/usr
lib standard libraries for porgrams
libexec
obj
bin, sbin local executalbe programs
src souce files
include libraries header files
local something loacl
ports fucking 'make install clean'
/var a lot of things
db database
pkg database for pkg and ports
ports
log system log
mail your mailbox
learn more:
http://www.freebsd.org/doc/handbook/dirstructure.html
mointing file system
'mount' command
most are disk partitions
network file servers (NFS)
memory disk emulators # man mdconfig
kernel components
for a new harddisk
sysinstall
configuration
fdisk lable
fd or swap
mount /dev/ad2sle /home2
Note: you should mount it on a empty direction
/etc/fstab
auto mount at boot time
'umount' command
usage:
unmount {node | devoce}
Ex. unmount /dev/ad0s1e
unmount -f # force unmount
lsof / fstat
file types # the first character of 'ls -l'
- regular file
b block device
c character device
d directory
l symbolic link
s socket
p named pipe
'file' command
determine file type
/usr/ports/sysutils/file
directory
. and ..
current directory and your father directory
mkdir / rmdir
make directory
remove directory
socket
created by socket()
local to a particular host
be referenced through filesystem object rather than a network port
process A process B
| write ^
V | read
+----------------------------+
| socket buffer |
| [UNIX kernel] |
+----------------------------+
named pipe # FIFO
'mkfifo' command
link
symbolic link
ln -s src dest
inode
a structure that records info of a file
'ls -i' to see each file's inode number
the inode structure
mode
owners
timestamps
size block
count
direct blocks
single indirect
double indirect
triple indirect
filesystem
boot blocks
super block
inode blocks
date blocks
hardlink and symbolic link
hardlink
associate two or more filenames with same inode
must in the same partition
ln src dest
symbolic link
A file which points to another pathname
ln -s src dest
file access mode
rwx for read, write, and exectue #value 421
Ex. rwxr-xr-x, 733
user, group, other privileges
'chmod' command
chmod access-string file
-R recursivily
directory must be x then you can cd into it
class operator access type
--------------------------------------------
u(user) +(add) r
g(group) -(remove) w
o(other) =(set exact) x
a(all)
setuid, setgid, sticky bit
the effective uid/gid will be set to the UID/GID of the file
setuid
passwd, chsh, crontab
setgid
top, fstat, write
sticky on directory (/tmp)
do not allow to delete or rename a file unless you are
the owner of the file
the owner of the directory
root
umask
shell built-in command
inference the degault permissions given to the files newly created
777 or 666 xor umask value
change file owner
'chown' command
'chgrp' command
-R recursivily
Ex.
chown foo bar
chown user:grp bar
FreeBSD bonus flags
'chflags' command
ls -ol
'schg' flag to protect important files
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