Brother Bird's Linux private cuisine-Basic study-NOTE 2

at syntax = = Note that entering the at is followed by the command line mode-------No matter what, it will only be executed once.

[Test @test test]# at [-m] Time (input work order)
[Test @test test]# atq (view current workflow)
[Test @test test]# ATRM [jobnumber] (removal process)

-M: When executing workflow at the at specification, mail the screen output to the user who entered the instruction
Time: The format of the times, there are several: ================== format has a variety of, but there is no interval or repetition of the form
hh:mm yyyy-mm-dd ex> 04:00 2002-05-30 (May 30 4 o'clock implementation)
HH[PM;AM] + number [Hours;days;weeks] ex> 4pm + 3 days (3 day later in the afternoon
4 o'clock)
hh:mm ex> 12:00 (today 12 points)
HH[PM;AM] [Month] [day] ex> 1pm May 30

Crontab = = Loop Execute = = The routine command of this loop is actually the Cron service (Crond)

Crontab-e <== to edit his own crontab content
Enter crontab edit content, use VI

Please note: If you only want to remove a crontab
, use CRONTAB-E to re-edit it, and if you use the-r parameter, all the crontab data contents will be deleted.

Crontab setting of the system:/etc/crontab

Crontab-e effect is actually/usr/bin/crontab this execution file,

Man 5 passwd??

Remember: When using Man in Linux, the parameter profile queries are set in 5来

Each time Windows allows only one user to log in. Of course, WindowsNT also has multi-user multitasking, however, because NT consumes too much system resources

Windows 2000 is not good enough, because sometimes it freezes. Linux is very good, almost can say
Never crashes because it can kill a trapped program at any time and then re-execute
The program without restarting the machine

ALT+F1~F7 switch to a different terminal interface 7 basic Windows: Linux default provides 6 text interface login window, and a graphical interface

If you want the work in the screen to be executed in the background, you can use &. However, because it is a background
execution, the output of the program does not appear on the screen, so special attention needs to be paid to the pipeline re-conduction of the output information. Other
Outside, how do I get the program to re-execute on the screen? Using FG

Of course, you can also use CTRL + Z to drop the current work in progress to the background---the biggest advantage is not afraid to be CTRL + C this interrupt instruction interrupt!!

16.3.2 JOBS,FG and Bg,kill----with convenient use!

[Root @test/root]# jobs
[1]+ Stopped Vi. BASHRC

FG and BG
[Root @test/root]# FG%number Move the instructions in the background to the screen
[Root @test/root]# bg%number A means of turning a program in the background from a stopped to a running, not allowing it to perform in the background

Parameter description:
%: followed by numbers, indicating jobs ' work code
Number: Work code

Kill
[Root @test/root]# kill-signal%number
Parameter description:
%number: Background work code, can use jobs query
Signal
-1: Re-read parameter profile (similar to reload)
-2: User interrupts the job, like using CTRL + C to interrupt a job
-9: Kill a job immediately, whether or not the work is a death program----forced termination

-15: Stop a job (this is the default)-----is to stop a job with normal program, what is called normal program?

Free is a simple command that is used only to view the memory situation. Since it is so simple, there is no need to make such an order alone ...
Parameter description:
-K: Display memory in Kbytes
-M: Display memory in MBytes

uname [-APNR]
Parameter description:
-A: List all system Information
-P: List CPU information
-N: List host names
-r: List Core version information

Nice [-N number] command
Parameter description:
-N: The following number is the Nice value
Example:
[Root @test/root]# nice-n-5 Find/-name core >/tmp/core
As mentioned earlier, Nice is used to adjust the execution priority of the program.

Renice [number] PID ...

Uptime how long has the current Linux host been powered on?

。 Basically, who and W
function is the same, only the WHO lists the user name and login time, W will list the user:
Source Address (IP): the From item;
Log in time: [email protected];
Work item: What item.

There's another whoami.

Last record one months

Example:
[Test @test/root]# hostname
test.linux.org

Ps-aux querying the relevant programs in the background of the current host environment

A: Choose to list All Programs
U: List all users ' programs
X: List of all TTY programs

TTY: Is the program executed for the login? If the Tty1-tty6

Ntpdate Time Server

Ntpdate time.stdtime.gov.tw

Clock–w

Talk about how Linux is powered on. The basic process is:
1. Load the BIOS hardware information;
2. Read the kernel Loader (i.e., lilo,grub,spfdisk, etc.) of the MBR to boot information;
3. Load kernel operating system core information;
4. The kernel executes the INIT program and obtains the running information;
5. Init executes the/etc/rc.d/rc.sysinit file;
6. Launch the core plug-in module (/etc/modules.conf);
7. init executes various batch files at run level (Scripts);

8. Init executes the/etc/rc.d/rc.local file;
9. Execution of/bin/login procedures;
10. After logging in, start with the Shell control console.

Ll/etc/sysconfig

Lilo older

Grub is a newer boot loader

Daemon literally means "guardian god", "demon".

Daemons currently has two basic models, namely

1 Stand_alone

2 Super Daemon: Compared to stand alone, this service is called by a unified daemon
The service. This unified and responsible daemon is inet service.

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There is a file in the Linux system that shows which port corresponds to the service, that is, the/etc/services file