Summary of common commands for Linux (System centos6.5)

Ls-al

List all files and subdirectories in the current directory

When a user logs on to Linux, the/etc/passwd file determines which shell to use, and the shell that the user uses is listed at the end of each line (/bin/bash)

Ls-f the file listed, the directory name followed by a symbol, columns such as the executable file plus "*" directory is added "/"

Nothing behind the CD will go back to the user's own home directory. If it's root, it's back to/root. This function is the same as cd~.

mkdir and RmDir mkdir is a new directory under the current directory, RmDir is used to delete the established directory

CP This command is equivalent to the copy command under DOS

Copy-r source file Destination file (target) parameter R refers to a subdirectory in a homologous file.

RM command is used to delete files, RM commands commonly used parameters are three:-i,-r,-f

The Rm-i test system asks us if we want to delete the test file, y/n to confirm whether to delete the test file

Rm-i directory names can be removed with subdirectories below the directory, which is more powerful than the rmdir mentioned above

Rm-f file name

This action can forcibly delete files without confirmation

So here to realize the seriousness of RM-RF, do not use it easily

MV The function of this command is to move the directory file, the extension function is to the directory file re-command

MV 1.tar 1.txt renamed 1.tar in/home directory to 1.txt

Cat This command is a very important command in Linux, his function is to display or connect the general ASCII text file

Cat file1 file2>file3 The command is to combine the contents of File1,file2 in a redirect to a file3 file

More is the instructions to display a generic text file, if a text file is too long for more than one screen, then cat view is not ideal, you can try more

PWD The function of this command is to display the user's current working path, directly enter the PWD to

User and User group commands

Useradd + username Create a new user account,

Useradd Tiantian System will create a new user Tiantian, the user's home directory is/home/tiantian

Useradd User name-G Group name-G group name-D Home directory name-p password

which

-g Specifies the user's first group

-g Specifies the user's secondary group

-d Specifies the user's home directory

-P Specify the password for the user

If you enter the following command:

Useradd oracle-g oinstall-g dba-d/home/oracle-p ora123

The system will create a user oracle,oracle user's first group is Oinstall, the minor group is Dba,home directory is/home/oracle, the password is ora123

userdel+ User name Delete an existing account

Groupadd + Group name create a new user group

groupdel+ Group name to delete a user group name that already exists

passwd command to change your password

passwd: After you enter this command, you will be prompted to enter the password and password confirmation once, you can complete the user password modification

In addition, Superuser can modify other user's password

passwd + user Name

Chmod is used to change the access rights of a file or directory. There are two ways to do this: one is a text setting that contains letters and operator expressions, and the other is a digital setting method that contains numbers.

1: Action object who can be any of the following letters or a combination of them

U means the user is the owner of the file or directory

G indicates that the same group user is all users with the same group ID as the file owner

O indicates other (others) users

A: Indicates all users (all) It is the system default value

2: The operation symbol can be:

+: Add a permission

-: Cancel a permission

=: gives the given permission and cancels all other permissions

3:mode represents permissions, and the commonly used parameters are:

R: Readable

W: Writable

X: Executable

The file text, the permission is set to: The file belongs to the master readable, writable, executable, and the file belongs to the same group of user-readable, other users are unreadable,

Chown: Used to change the owner or group of a file or directory, such as the root user to copy one of their own files to the user Oracle, in order for the user Oracle to access this file, the root user should be the owner of this file to Oracle

chown[User: Group] File

Example: Change the owner and the group of the test file to Oracle and DBA respectively

Chown ORACLE:DBA Text

Create a new directory with root and create a new file under it, authorizing both of the following:

chmod o=r XXX

Then switch to the normal user, try to open the directory and discover the failure

When the following authorization is found, the directory and file can be opened but cannot be modified:

chmod o+x XXX

Note that the R permission is readable for the file, but for the directory, you must have X permissions to enter the directory.

PS: View Process

-F: Full format display

-e: Show All Processes

-L: Long format display

The items displayed are UID (with ID of the execution process), PID (process), PPID (parent process ID), TTY (terminal name) stime (process start time), and the time (Process execution times) CMD (command line input for the process)

However, it is common to use PS-EF output more than Ps-ef | grep Oracle

The basic function of top and PS commands is the same, showing the current process and other conditions of the system. But top is a dynamic display process, q exits

Kill + Process Number End process

KILL-9 1234 terminates a process with PID process number 1234 (-9 means force stop)

Cron is used to accomplish timed tasks

A user with user name is the crontab file that corresponds to it should be/var/spool/cron/user. In other words, the crontab file with the user command is stored under the/var/spool/cron directory. The cron command also searches for/etc/crontab files, which are written in different formats. After Cron starts it will first check if a user has set up the crontab file

If not, go to hibernation and release the system resources. It wakes up every minute. See if there are currently any commands that need to be run

can use

crontab-l command to view cron tasks that are currently in existence

Crontab-r Delete the current user's cron process

CRONTAB-E Adding a scheduled task

Time-sharing Week

DF-K will show disk space usage for each partition.

Reboot System restart command

Shutdown shutdown system {option} {time} {warning message}

-K: does not really shut down and just sends a warning message to all users

-R: Restart immediately after shutdown

-H does not restart after shutting down the machine

-F Fast shutdown reboot Skip Fsck

-N Fast shutdown without init program

-C cancels an already running shutdown

Shutdown-r +10 system shuts down in 10 minutes and restarts immediately

Shutdown-h now system shuts down immediately and does not restart

Noun Introduction:

Console: (console), which is our common human-computer interface using a string interface, such as DOS. The console command we're talking about is a command that can be operated by the operating system via the character interface, such as a DOS command, which is a console command.

Linux is a multi-user operating system, which means that it can accept multiple user logins at the same time. Linux also allows one user to log on multiple times, because Linux and UNIX provide access to the Virtual console, allowing users to log in from the console multiple times at the same time

Summary of common commands for Linux (System centos6.5)