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# ssh to host 
ssh user@hostname

# generate ssh key
ssh-keygen -t rsa -C "kaixuan@example.com"

# copy local ssh public key to remote host
ssh-copy-id user@hostname

# add private key to ssh-agent

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# 如果是通过 apt-get 或 yum 安装的 redis
/etc/init.d/redis-server stop
/etc/init.d/redis-server start
/etc/init.d/redis-server restart


# 如果是通过源码安装的 redis
./redis-cli -h 127.0.0.1 -p 6379 shutdown
./redis-cli -a 密码 -h 127.0.0.1 -p 6379 shutdown # 如果有密码

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# 按状态统计
netstat -nat | awk '{print $6}' | sort | uniq -c |sort -rn

# 按本机到外部80端口的访问统计
netstat -nat | grep ESTABLISHED | awk '{print $5}' | grep :80 | sort | uniq -c | sort -rn

# 按外部到本机80端口的访问统计
netstat -nat | grep ESTABLISHED | awk '{print $4}' | grep :80 | sort | uniq -c | sort -rn

# ESTABLISHED	正在通信

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1. Sort Lines.

2. Find And Replace. (确保正则模式打开)
	^(.+)$[\r\n](^\1$[\r\n]{0, 1})+
	\1\n

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ulimit -a
ulimit -n

# check hard limit
ulimit -Hn

# check soft limit
ulimit -Sn

# current session change

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# list enabled ports/services
firewall-cmd --zone=public --list-ports
firewall-cmd --zone=public --list-service

# enable http(s) port (80 443) using the firewall-cmd
firewall-cmd --permanent --zone=public --add-service=http
firewall-cmd --permanent --zone=public --add-service=https
firewall-cmd --reload

# enable specified port 

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# check selinux status (SELinux status & Current mode)
sestatus
---
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled

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# CentOS 6.x
hostname newHostName
vi /etc/sysconfig/network

# CentOS 7.x
hostnamectl set-hostname newHostName

# Change oldHostName to newHostName
vim /etc/hosts

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# 查看 Linux 内核版本信息
cat /proc/version

uname -a

uname -r


# 查看 Linux 系统版本信息
cat /etc/issue

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yum install http://opensource.wandisco.com/centos/6/git/x86_64/wandisco-git-release-6-1.noarch.rpm -y
yum --disablerepo=base,updates --enablerepo=rpmforge-extras update git -y
yum update git -y
git --version