: useradd, userdel, groupadd, groupdel. : .
usermod groupmod . .
passwd , .
chown chgrp. .
chmod.
( ) , .
GRUB
GRUB (. GRand Unified Bootloader) GNU. GRUB .
GRUB , .
GRUB ,
'e' . . 'single' . 'b' . , init=/bin/bash 'b'
, , . passwd < >
reboot
GRUB
GRUB - , live CD
: .. BIOS, ,
) , 4 : (UID), (GID). , . , . , .
su [-] [_ [... ]]
su , , . root.
|
|
su ( root). , su , , , .
su . $HOME $PATH, .. /root, $PATH /sbin /usr/sbin. su $HOME , , , - su, (, ) , .
, exit, logout Ctrl-D.
Unix su. sudo, . ( ), , , ( /etc/sudoers, . man sudoers ). visudo /etc/sudoers. sudo , root. "sudo -i".
sudo () root, :
o root (sudo ).
o ( ), . root sudo.
o /: sudo, . ...
: ,
) ,
UNIX .
Unix , 9- . , , . , , . 16- 4- , . 4 .
. , (owner), (group owner), (everyone).
flag user group other
# rwx rwx rwx
(flag) :
-
l (symbolic link)
d (directory)
|
|
b (block device)
c (character device)
p , fifo (fifo device)
s Unix (unix domain socket)
OCT BIN Mask
0 000 - - -
1 001 - - x
2 010 - w -
3 011 - w x
4 100 r - -
5 101 r - x
6 110 r w -
7 111 r w x
(9 ). , - , - . , , , 777 (rwxrwxrwx). , SUID, SGID Sticky-. . , 4. , 4- , 0744.
: , , .
, , . , SUID (Set User ID), , , .
SUID, , , , , . , , , .
, , . , , , .
(EUID) -, UID , .
SUID. . /etc/shadow:
-rw-r----- 1 root shadow 500 2005-03-02 17:14 /etc/shadow
shadow, root. , . - !
passwd.
-rws--x--x 1 root bin 37880 2004-06-21 23:20 /usr/bin/passwd*
s, x . , SUID. , , root! Root shadow, .
UNIX- SetGID, . , , , SetGID, - .
SGID . .
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|
, . , , . , , . .
(SetUID SetGID), , , . SetGID, , , , , , . SetGID. , . SetUID, , .
.
, (, ). , .
, . , , (, ). , . sticky bit. , , .
: drwxrwxrwt 5 root root 4096 2005-06-05 17:28 /var/tmp/
t . , stiky-.
:
UNIX . , UNIX , , , . , .
UNIX , . , , , ( ). , : .
UNIX (ACL), .
. , ( ACL), .