Linux Learning Notes (System daily management-3)

Crontab: Task Scheduler

-e: Create and edit the crontab configuration file, the file is automatically installed when the edit is finished

-L: Display the contents of the Crontab configuration file on the standard input device

-r: Delete crontab configuration file

Five fields: Minute, time, day, month, week

eg

Empty/var/log/champly.log log 1:20 A.M. every day

1 * * * echo "0" >/var/log/champly.log

Execute every 8 hours ...

0 */8 * * * ...

Anacron: Same as Crontab

NTSYSV: Can see the list of services

If the command is not installed using yuminstall-y NTSYSV

Chkconfig:

Chkconfig--list: Viewing the operation of various system operating levels

Chkconfig--level [345] ServiceName on/off:

Turn services on or off at a certain run level, default 345
Chkconfig--add/del ServiceName: Add your own startup script

Under/ETC/INIT.D this folder

Linux system logs:

/etc/rsyslog.conf: Configuration file, see where the log is placed, it is best to use the default
/var/log/messages: Core System log files
Archive one log per week

/etc/cron.daily/logrotate Configuration Archive
/etc/logrotate.conf:
Messages is generated by the syslog: This daemon, if this service is stopped, the system will not produce/var/log/messages
/VAR/LOG/WTMP: Store User Login History last

Last: User can log in history

If it's deleted, last is gone.
/VAR/LOG/BTMP: Store Invalid login history

LASTB Viewing Invalid login history

/var/log/maillog: Log Mail logs
/var/log/secure: Security-related logs
/VAR/LOG/DMESG: Storage System boot hardware thrown log, reboot once, rewrite once

dmesg : Check the kernel error log (can see if the attack, whether overflow ...) ）

What's the first thing to think about is to check the system log, to know exactly where the problem

Exec:

EXEC must be used in conjunction with find:

Use the {} instead of each file found in Find as an object

must be added after \; (the semicolon obtained by escaping)
Find files with the current directory creation time greater than 10 days and delete:

Find. -mtime +10-exec rm-rf {} \;
To change file names in bulk:

Find./*-exec mv {} {}_bak \;

Xargs used behind the pipe symbol

Find.  –mtime +10 | Xargs RM-RF
ls-d./* | Xargs-i {} mv {} {}_bak
Can turn multiline into one line ls | Xargs

Screen

Installation via Yum install-y screen

Allows the program to log logs in the background

Use screen to start a shell, even if the current link is closed, the program can run the end of the

Equivalent to a child shell

Screen-ls: can see ID number

Screen-r ID/Name: can be counted into a screen

Screen-s (UPPERCASE) Name: You can customize a name

Curl: You can access a website in the command window, out of an HTML source

-I: Can look at head

-X: You can specify a proxy

/etc/hosts can set the host

-V: You can view the procedure

-U user:password: Specify user name and password access

-o filename URL: The name of the specified file can be downloaded

-o URL: Do not specify a name, the name is the real name

Ping: Testing the connectivity of the network

-C: You can specify the number

Telnet: Testing the connectivity of the port

Traceroute: As with Windows tracert, you can see what's wrong with the route.

Dig URL: You can see the domain name and IP equivalent to Windows nslookup

@dns: You can specify a DNS

Nc-z-w2 URL Port1-port2: Can scan ports open from Port 1 to Port 2

-Z: Show results, no display

-w2:2 seconds Timeout

SS: Similar to netstat in Windows, see Open ports

April 20, 2015

By:champly

Linux Learning Notes (System daily management-3)