Add user Two-step walk: 1.useradd username 2.passwd PS
Rights Management Commands
Command name:chmod->>change The permissions mode of a file
Command path:/bin/chmod
Execute Permissions: All Users
Syntax: chmod [{u g o} {+-=}{rwx}][file or directory]
[mode = 421] [File or directory]
+: Increase Permissions
-: Reduce permissions
=: Give permission directly
the focus of mastery is to use the digital way of authority control, r=4 w=2 x=1.
rwxr-xr--= 754
Rw-r-x--x = 651
Example: chmod g+w file
chmod 777 File
RWX Permissions in a file
R-cat, more, head, tail
W-echo, vi modify content, cannot delete
X-Commands, scripts
RWX Permissions for the directory
R-ls
W-touch, mkdir, rm delete new
X-Enter the directory
Function Description: Change file or directory permissions
Command name:chown->>change file ownership
Command path:/bin/chown
Execute Permissions: All Users
Syntax: chown [user] [file or directory]
Example: Chown Nobody file to change the owner of files to nobody "system comes with"
Command name:chgrp->>change file group ownership
Command path:/BIN/CHGRP
Execute Permissions: All Users
Syntax: chgrp[user [file or directory]
Example: chgrp Nobody file to change the owning group of files for ADM "System comes with"
Command name:umask
Command path:/bin/umask
Execute Permissions: All Users
Syntax: Chgrp[-s]
-S displays the new file or directory default permissions in the Rwx form
0022
0-Special Permission bit
022-user permission bit, permission mask value
Its true value is 777-022 = 755
Linux permissions rule: Files created by default cannot be granted discretionary x permissions
So a file created with touch, with a value of 644, can mask many attacks, trojans and viruses.
Function Description: Displays, sets the default permissions for the file.
File Search Command
Command name:which
Command path:/bin/which
Execute Permissions: All Users
Syntax: which [command name]
Function Description: Displays the directory where the system commands are located and can only find commands
Example: Which LS
Command name:Find
Command path:/usr/bin/find
Execute Permissions: All Users
Syntax: find[search path [search keywords]
Function Description: Find files or directories
Example:find/etc-name init---->>> Find file init in directory/etc, files containing the init keyword are not searched
When you don't remember your full name, you can use wildcards to search
* matches any character? Match a single character
Find /-size +204800---->>> look for files larger than 100MB in the root directory
Less than how much to use-204800
100MB = 102400kb = 204800 block 1block = 512 bytes
find/home-usr Samlee->>>>> Find the file owner-Samlee under the root directory
find/etc-mmin-120 files modified in etc directory for two hours
Time
1, Days CTime, Atime, Mtime
2, Minutes Cmin, Amin, Mmin
-like, + more than
C-change change: Indicates that the properties of the file (owner, owning group, permissions, and so on) have been modified
A-access Access:
M-modify: Indicates that the contents of the file have been modified
Connector-a and-o or
Connector find ...-exec command {} \; where {} represents the result of the Find query
-ok Ask for confirmation
Find/etc-size +163840-a-size 204800
Files larger than 80m and less than 100M
-type Lookup based on file type F binary file l Soft link file-D directory
-inum Search based on I node
Command name:Locate
Command path:/usr/bin/locate
Execute Permissions: All Users
Syntax: locate[keywords]
Function Description: Find a file or directory, based on the installation and the regular update of the contents of the database to find and do not need to find the entire hard disk, generally with updatedb use
The speed is much faster than find.
Example: Locate file
Command name:updatedb--->> update the slocate database
Command path:/usr/bin/updatedb
Execute permissions: Root
Syntax: UpdateDB
Function Description: Create a database of the entire system catalog file
Example: UpdateDB
Command name:grep
Command path:/bin/grep
Execute permissions: All user
Syntax: grep[specified string [source file]
Function Description: Searches the file for the specified string and outputs
Example: grep ftp/etc/services
Command name: Man---->> manual
Command path:/usr/bin/man
Execute permissions: All user
Syntax: grep[command or config file command or configuration file just write the name, don't write absolute path
The first is the Help for the command, and the fifth is the help for the configuration file. Use when a name is used to differentiate even if the command is a configuration file
Mans 1 Password
Mans 5 Password
Function Description: Get help information
Example: Man ls
Command name:Info---->> Information
Command path:/usr/bin/info
Execute permissions: All user
Syntax: info[command or config file command or configuration file just write the name, don't write absolute path
Function Description: Get help information, and man's difference is only in the way the content is presented.
Example: Info ls
Command name:Whatis Apropos Makewhatis
Command path:/usr/bin/whatis apropos
/usr/sbin/makewhatis
Execute permissions: All User,root
Syntax: whatis[command or config file command or configuration file just write the name, don't write absolute path
Function Description: The most basic usage of the Extract command
Example: Whatis ls
Apropos fstab equivalent to Man-k
Command--help to list the options for the command
Help built-in commands: View the shell's built-in commands
Linux learning the next day (Rights Management commands, file search commands, help commands)