Linux常用命令

查看gcc版本

gcc -v

gcc安装命令

yum -y install gcc

安装openssl

# openssl是web安全通信的基石，没有openssl，可以说我们的信息都是在裸奔。。。。。。
yum install -y openssl openssl-devel

安装nginx

yum install -y nginx

启动并设置开机自启

sudo systemctl start nginx
sudo systemctl enable nginx

开启防火墙

systemctl start firewalld.service  

关闭防火墙

systemctl stop firewalld.service

重启防火墙

firewall-cmd --reload

开启端口

firewall-cmd --zone=public --add-port=80/tcp --permanent
#重新加载
firewall-cmd --reload

查看已开放的端口

firewall-cmd --list-ports

解压jdk安装包

# 解压
tar -zxvf jdk-8u271-linux-x64.tar.gz
# 修改解压后的文件名称为jdk1.8
mv xxx/ jdk1.8

配置环境变量

vim /etc/profile
# 在最后边加
# JAVA环境变量
JAVA_HOME=/xxx/xxx/xxx
PATH=$JAVA_HOME/bin:$PATH
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export JAVA_HOME
export PATH
export CLASSPATH

测试是否安装成功

[root@iZ2ze7jmwvt3iec793aif4Z java]# java -version
java version "1.8.0_271"
Java(TM) SE Runtime Environment (build 1.8.0_271-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.271-b09, mixed mode)
[root@iZ2ze7jmwvt3iec793aif4Z java]# javac
Usage: javac  
where possible options include:
  -g                         Generate all debugging info
  -g:none                    Generate no debugging info
  -g:{lines,vars,source}     Generate only some debugging info
  -nowarn                    Generate no warnings
  -verbose                   Output messages about what the compiler is doing
  -deprecation               Output source locations where deprecated APIs are used
  -classpath           Specify where to find user class files and annotation processors
  -cp                  Specify where to find user class files and annotation processors
  -sourcepath          Specify where to find input source files
  -bootclasspath       Override location of bootstrap class files
  -extdirs             Override location of installed extensions
  -endorseddirs        Override location of endorsed standards path
  -proc:{none,only}          Control whether annotation processing and/or compilation is done.
  -processor [,,...] Names of the annotation processors to run; bypasses default discovery process
  -processorpath       Specify where to find annotation processors
  -parameters                Generate metadata for reflection on method parameters
  -d              Specify where to place generated class files
  -s              Specify where to place generated source files
  -h              Specify where to place generated native header files
  -implicit:{none,class}     Specify whether or not to generate class files for implicitly referenced files
  -encoding        Specify character encoding used by source files
  -source           Provide source compatibility with specified release
  -target           Generate class files for specific VM version
  -profile          Check that API used is available in the specified profile
  -version                   Version information
  -help                      Print a synopsis of standard options
  -Akey[=value]              Options to pass to annotation processors
  -X                         Print a synopsis of nonstandard options
  -J                   Pass  directly to the runtime system
  -Werror                    Terminate compilation if warnings occur
  @                Read options and filenames from file

使用root用户登录，添加用户

# useradd -d /为此用户设置主目录 -m 用户名
useradd -d /xxx -m xxx

设置密码

[root@iZ2ze7jmwvt3iec793aif4Z shell]# passwd xxx
Changing password for user xxx.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.

登录测试

列出所有连接

netstat -a

只列出TCP或UDP协议的连接

#列出TCP协议的连接
netstat -at
#列出UDP协议的连接
netstat -au

禁用反向域名解析，加快查询速度

# 默认情况下 netstat 会通过反向域名解析技术查找每个 IP 地址对应的主机名。这会降低查找速度。如果你觉得 IP 地址已经足够，而没有必要知道主机名，就使用 -n 选项禁用域名解析功能。
netstat -ant

只列出监听中的连接

netstat -tnl

获取进程名、进程号以及用户id

sudo netstat -nlpt

打印统计数据

# netstat 可以打印出网络统计数据，包括某个协议下的收发包数量
# 如果想只打印出 TCP 或 UDP 协议的统计数据，只要加上对应的选项（-t 和 -u）即可
netstat -s

打印active状态的连接

netstat -atnp | grep ESTA
# 配合watch命令监视active状态的连接
watch -d -n0 "netstat -atnp | grep ESTA"