Shulou(Shulou.com)06/03 Report--

Linux commands--system application commands

1. Time management

date: Display system time

clock: Display hardware time

hwclock -W: Synchronizes system time to hardware time

hwclock -s: synchronizes hardware time to system time

cal: Display calendar

Date of modification:

The order dated 9 January 1996 reads as follows:

#date -s 1/9/2009

Date and time set: August 8, 2008 12:00

date -s "2008-08-08 12:00:00"

Set the time to 14:36 p. M.

date -s 14:36:00

Remember to synchronize bios time after changing the time:

Synchronizing the BIOS clock forces the system time to be written to CMOS with the following commands:

#clock -w

2. Help orders

Internal command help: help COMMAND

External Command Help: man COMMAND

Command manual: manual

whatis COMMAND: Shows which section of man help this command is in.

============================================================

The man's command:

Space: Flip back one screen

b: Turn forward one screen

ENTER: Turn back one line

k: forward one line

============================================================

key lookup

/KEYWORD: search keywords backwards

？KEYWORK: Search keywords forward

n: Next keyword position

N: previous keyword

Q: Exit man help

3. System information

switch directory

cd Back to user's home directory

cd ~username: Enter the specified user's home directory

cd -: toggles between the current directory and the previous directory

cd ..: Switch to its parent directory

cd /home Go to '/ home' directory '

4、alise

Define aliases for shell commands

alias CMDALIAS=COMMAND

unalias CMDALIAS is an alias for the undo command

5、printenv

Display current variable information

6、whoami

Show who the current user is

su -: When switching, the user before switching is displayed

7、who

View the user currently logged into the system and the terminal he logged into

-r: Displays the current operating level

-H: The first time the list shows the column names

w: Display more detailed information than who

8、last

Displays the login log (/var/log/wtmp file) on the current system, including system user and restart information

last -n number: only shows the most recent login information

9、lastb

Show user error login common sense

lastb -n Number: Displays only the last few wrong logins

10、lastlog

Displays information about each user's last successful login

lastlog -u USERNAME: Displays the last login information of the specified user

11、basename

Displays the base name of a directory

basename /etc/abc/me Show me directly

$0: Command name or path to script itself.

basename $0: Call script path directly

12、mail

Mail view, you can view mail, after viewing will be placed in the user's home directory mbox folder.

-s theme

mail -s "How are you " root

cat /etc/fast | mail -s "How are you " root

13、hostname

hostname: Displays the name of the current host

hostname hostname: change hostname

14、fuser

Verify that the file or socket in use is being used

-v: View processes in use on a file

-k: Give the visiting process to kill

-km: Shut down all processes on the mount point

15、watch

Periodically execute specified commands and display results in full screen mode

Format: watch -n # 'COMMAND'

-n #: Specify the cycle, unit is seconds, default is 2 seconds

16、ps

View process information

BSD style common options:

a: Display all terminal-related processes?: It is not related to the terminal.

x: Displays all processes unrelated to the terminal

u: Display progress information

aux: combined use

SysV style common options:

-elF: View all progress information (e: All progress)

F: No details.

-o PROPERTY: Specifies property display

17、top

Dynamic display of process information

Support interactive, interactive commands

M: Sort by resident memory size

P: Sort by percentage of CPU usage

T: Sort by cumulative time

l: Whether average load and startup time are displayed

t: Whether to display information related to progress and CPU status

m: Whether to display memory-related information

c: Does the full command line information appear?

Q: Exit top

k: Terminate a process

Common options:

- d1: Refresh every few seconds

-b: batch mode display

-n #: How many batches are displayed in batch mode

18, foreground and background

foreground job: occupies command prompt

Background jobs: After startup, the command prompt is released, and subsequent operations are completed in the background

Front Desk--> Backstage:

Ctrl+Z: Send jobs to background

bg: Keep jobs stopped in the background running

bg [%JOBID]:% can be saved

fg: Send foreground jobs to background

fg [%JOBID]: % Can save SysV style common options:

-elF: View all progress information (e: All progress)

F: No details.

-o PROPERTY: Specifies property display

19、shutdown

shutdown [-akrhHPfnc] [-t secs] time [warning message]

shutdown: Command to shut down

-r now: restart immediately

-t sec: a few seconds later

-h now: shut down immediately

20、uname

uname -r: View system kernel version

uname -a: System version information

21、dd

Convert and copy files, copying the lowest data stream

Format: dd if= data source of= data storage destination bs=#how large is a unit count=#copy

How many times does this data

for example

dd if=/dev/sda of=/mnt/usb/mbr.backup bs=512 count=1

Can be used to backup MBR

Create Loop File

dd if=/dev/zero of=/var/swapfile bs=1M count=1024 This command creates a 1G image file, which can be directly mkswap and can be started.

/dev/zero is a bubble device that spits zeros out all the time

22、mktemp

mktemp: Create temporary files

mktemp /tmp/file.XX(XX stands for files automatically generated by the system) Generate temporary files

mktemp -d /tmp/file.xx: Generate temporary directory

23、at

at: Specify a task to be performed at some point in the future

time format

Absolute time: HH:MM DD:MM:YY MM/DD/YY

Relative time: now+#(minutes,hours,days,weeks)

Blur time: noon,midnight,teatime

at -l: Display your list of assignments

at -d Job Number: Delete Job

24、cron

cron: uninterrupted permitted service

System cron definition format:

Minutes Hours Days Months Weeks User Tasks

User cron task definition format

Definition file/var/spool/cron/USERNAME

Format: Minute Hour Day Month Week Task

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.