Linux daily operation and maintenance management

1 , viewing the system load command

W command: Main view CPU Load

Load average: Load within five minutes of load for 15 minutes within one minute

The load is related to the number of CPU cores and the number of CPU cores viewed:

# Cat/proc/cpuinfo | grep ' Processor ' | Wc-l

Uptime can also display CPU load

2 , Vmstat command

# vmstat 1 5

1 represents once per second, 5 represents five times

R column: Represents a process that runs within one second

Column B: Blocked process

SWPD column: How much data is exchanged, in kilobytes

Free column: Remaining memory

Buff Column: Buffering

Cache columns: Caching

Si column: Swap in enter into memory data

So column: Swap out read out of memory

BI columns: Read disk, normal server hard disk continues to exceed 1000 note server pressure read frequently

Bo Column: Write disk

In column: Number of endpoints

CS Column: Context switch

US column: Percentage of CPU consumed by the user-state process

SY column: Kernel-state process consumes percent of CPU,

ID Column: Idle

WA column: Waiting

St Column: Stolen

3 , top command

PID: Under the/proc directory

User: The process to which users run

FR: Value range 0 to 39, process priority, lower value priority higher

NI: Value range 20 to 19, process priority

VIRT: Total amount of virtual memory used by the process =swap+res

RES: The physical memory that the process uses, not swapped out

SHR: Contributing Memory

S: Process state d= non-interruptible sleep state r= run s= sleep t= track/stop z= zombie Process

%CPU:CPU usage Rate

%MEM: Memory Utilization

Time+: Time to use CPU

COMMAND: Process Name

4 , SAR command (view network card traffic)

# sar-n DEV 1 10

Display once per second, display 10 times, network card traffic statistics

The history of the SA is recorded in the/var/log/sa directory

Use the # sar-n dev-f sa27 to view the history of number 27th

# sar-q View Load

# sar-b View Disk

5 , free command

# FREE-M displays memory usage by megabytes, which by default is K

Total: Amount of memory

Used: Memory usage

Free: Memory remaining condition

Buffers: Data that will be written to disk in memory

Cached: Putting data from a disk into memory

6 , PS command

# How to use PS Aux:bsd style

User: The process to which users start

PID: Process ID

%cpu:cpu percent usage

%MEM: Percent Memory usage

VSZ: Virtual Memory size

RSS: The size of real memory

TTY: Terminal

STAT: Process state S: Hibernate, S main process;< high priority, N priority low, + foreground running process; R running process; l locked process; l multi-threaded process; z zombie process; x dead process; t paused process

Start: Startup time

Time: CPU-intensive

COMMAND: The name of the process

7 , netstat command

# NETSTAT-LNP View servers listening to those ports

# Netstat-an | grep 92.168.83.50:3402 | Grep-ic Estab View the number of connections

8 , Tcpdump, and Tshark tools

# tcpdump-nn-i Eth0-c 5

Crawl five packets on the eth0 NIC

# tcpdump-nn TCP and Port 22-c 5

# TCPDUMP-NN-S0 TCP and Port 22-c 10-w Test.cap

Tshark tools need to install Wireshark binary packages

# tshark-n-T a-r http.request-t fields-e "Frame.time"-E "ip.src"-E "http.host"-E "Http.request.method"-E "http.re Quest.uri "

9 , SELinux

View selinux Status: # Getenforce

Temporary shutdown selinux:# Setenforce 0

Permanently closed: # sed-i ' s/selinux=enforcing/selinux=disabled/g '/etc/selinux/config

If the Libselinux-utils package is not installed with the Getenforce and Setenforce commands

Ten , NetFilter ---iptables firewall

Table-->chain Chain

# iptables-t FILTER-NVL//View the rules of the filter table

# iptables-t NAT-NVL//view NAT table rules

# iptables-t MANGLE-NVL//view rules for mangle tables

# iptables-t filter-a input-p tcp--dport 80-s 192.168.1.135-j REJECT

-T: Specifies the name of the table to manipulate

-A: Append a rule

-I: inserting a rule

-D: Delete a rule

-P: Set default rules

-P: Specify protocol

--dport: Specify port number

-S: Specify Source IP

-J: Specify the processing mode; REJECT: Reject; drop: discard; Accept: Acceptance

# Iptables-f//Empty firewall rules

# service Iptables save//Keep a well-written firewall rule permanently

# iptables-save >/tmp/iptbales Backup firewall rules

# Iptables-restore < iptables//recover firewall rules

INPUT drop;192.168.1.1/24 Accept;all, all of the accept;

#/bin/bash

Iptables= "/sbin/iptables"

$iptables-F

$iptables-P INPUT DROP

$iptables-P OUTPUT ACCEPT

$iptables-P FORWARD ACCEPT

$iptables-A input-s 192.168.1.1/24-p TCP--dport 22-j ACCEPT

$iptables-A input-p TCP--dport 80-j ACCEPT

$iptables-A input-p TCP--dport 21-j ACCEPT

$iptables-A input-p TCP--dport 22-j drop the remaining network segments do not allow connection to port 22

One , cron Scheduled Tasks

# crontab-l

-L: View task Schedule

-E: Edit Task Schedule

-r: Delete Task schedule

First paragraph *: minutes

Second segment *: Hours

Third paragraph *: day

Fourth paragraph *: month

Fifth paragraph *: week

A , System Services

# NTSYSV command belongs to NTSYSV package, no command can be installed, control boot-up service by a similar graphical interface

# Chkconfig--list can also use this command to see which services are booting from

# chkconfig VSFTPD on/off allows some services to turn on or off at boot time

# chkconfig--level 23456 vsftpd on specifies the open or closed state of some services at startup level

# CHKCONIFG--add 123 adds 123 service to the boot entry, but 123 must be in the/ETC/INIT.D directory and is an executable file

- , Linux logs

The core system log is stored in the/var/log/directory

Log format and storage in/etc/logrotate.conf and/etc/logrotate.d/directories

View log of User login history/var/log/wtmp The log cannot be viewed directly and can be viewed with the last

Viewing the history of invalid logins/var/log/btmp The log cannot be viewed directly and can be viewed with LASTB

/var/log/maillog Mail-related logs

/var/log/secure authentication-related logs, such as the FTP logon situation

/VAR/LOG/DMESG some hardware-related logs during system startup

- , Xargs, and exec use

# Find. -name passwd-exec cp {} {}.bak \;

# Find. -name passwd | Xargs-i cp {} {}.bak

Two commands execute the same result

# ls *.bak | Xargs Rm-rf can also delete files like this oh, very cool ...

the , Screen command

Nohup Sleep & Drop in the background exit terminal is not interrupted and logs are logged

Screen Command Input screen package

How to use:

# screen

Input commands such as top

Then press Ctrl+a+d to exit.

# Screen-ls Viewing background programs

# screen-r ID View background program

Press CTRL+D or ESC to exit screen

16. Curl Command

# Curl Www.baidu.com View Baidu's text page

# curl-i www.baidu.com View status information of Baidu, etc.

# curl-x61.135.169.125:80-i www.baidu.com Specify proxy server

# curl-x61.135.169.125:80-iv www.baidu.com View Browse Baidu Yes visit process

# curl-u Fanjinbao:fanjinbao www.fanjinbao.com Access User name Password page

# Curl-o http://www.baidu.com/img/bdlogo.png Direct download of bdlogo.png pictures

# Curl-o fanjinbao.png http://www.baidu.com/img/bdlogo.png Download and rename to Fanjinbao.png

Linux daily operation and maintenance management