Linux file permissions

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[Email protected] ~]# chmod 575 a.txt

[Email protected] ~]# ls-l a.txt

-r-xrwxr-x 1 root root 0 March 19:09 a.txt

# chmod-r 777 xx/Recursive Change permissions

# chmod u=rwx,g=rwx,o=rwx xx a=rwx all +-

# chmod a-w XX

# chown Root:root XX

650) this.width=650; "src="/e/u261/themes/default/images/spacer.gif "style=" Background:url ("/e/u261/lang/zh-cn/ Images/localimage.png ") no-repeat center;border:1px solid #ddd;" alt= "Spacer.gif"/>

Cut-d delimiter-F Number selected column-C by character

# who | Cut-b 10-14

Tty1

pts/0

# Who|cut-b 3-

Who|cut-c 3-5

[Email protected] ~]# cat/etc/passwd|head-n 5| cut-d:-F 1

Root

Bin

Daemon

cd/

Lp

Chgrp

# Useradd Yy-g He

$ ll

-rw-r--r--1 XX He 15 March 20:20 a

Permission to delete a file is controlled by the permissions of the parent directory, regardless of the permissions on the file itself

650) this.width=650; "src="/e/u261/themes/default/images/spacer.gif "style=" Background:url ("/e/u261/lang/zh-cn/ Images/localimage.png ") no-repeat center;border:1px solid #ddd;" alt= "Spacer.gif"/>

650) this.width=650; "src="/e/u261/themes/default/images/spacer.gif "style=" Background:url ("/e/u261/lang/zh-cn/ Images/localimage.png ") no-repeat center;border:1px solid #ddd;" alt= "Spacer.gif"/>

# umask

0022

File 666-022

Catalog 777-022

The average user's umask may not be 002 unless the following conditions are met

# Vi/etc/profile

If [$UID-gt 199] && ["' id-gn '" = "' Id-un '"]; Then

Umask 002

Else

Umask 022

Fi

# Vi/etc/login.defs

UMASK 077 for home directory

Suid sgid Sticky bit permissions

Setuid can allow the normal user to run the root role

# chmod U+S/ETC/PASSWD

-rwsr--r--

# Find/usr/bin-type F-perm 4755 | Xargs ls-l

-rwsr-xr-x. 1 root root 54240 January 2012/usr/bin/at

-rwsr-xr-x. 1 root root 66352 December 8 2011/usr/bin/chage

-rwsr-xr-x. 1 root root 51784 November 2013/usr/bin/crontab

-rwsr-xr-x. 1 root root 71480 December 8 2011/usr/bin/gpasswd

-rwsr-xr-x. 1 root root 36144 December 8 2011/usr/bin/newgrp

-rwsr-xr-x. 1 root root 30768 February 2012/usr/bin/passwd

-rwsr-xr-x 1 root root 27576 September 2013/usr/bin/pkexec

# chown. xx/home/admins/

# chmod 770/home/admins/

# chmod 2770/home/admins/Directory group names are automatically inherited from the following files

# ls-ld/home/admins/

DRWXRWS---2 root xx 4096 March 22:07/home/admins/

# ls-l/home/admins/xxxxx

-rw--w--w-1 root xx 0 March 22:09/home/admins/xxxxx

# chmod 4755 A

-rwsr-xr-x

Setuid 4000 + Setgid 2000 = 6755

-rwsr-xr-x-rwxr-sr-x

# chmod U+s A # chmod g+s a

650) this.width=650; "src="/e/u261/themes/default/images/spacer.gif "style=" Background:url ("/e/u261/lang/zh-cn/ Images/localimage.png ") no-repeat center;border:1px solid #ddd;" alt= "Spacer.gif"/>

When coincident with X is the lowercase s.

sbit Sticky bit Permissions 1000 can only be deleted by primary and Root: Sharing files, others can not move other people's things.

# ls-ld/tmp/

DRWXRWXRWT. 3 root root 4096 March 21:46/tmp/

chmod 7755 Test

Chattr +i A cannot be deleted.

Chattr +a A can only be appended

Lsattr

Setfacl Getfacl

Linux file permissions