ifconfig 命令

ifconfig在centos6中是默认安装的，centos7版本默认是没有这个命令的，需要使用yum来进行安装： yum install net-tools
使用ifdown和ifup单独启动个别网卡

[root@localhost /]# ifdown enp0s3 && ifup enp0s3
成功断开设备 'enp0s3'。
成功激活的连接（D-Bus 激活路径：/org/freedesktop/NetworkManager/ActiveConnection/2）

设置虚拟网卡，拷贝原网卡文件，修改网卡配置文件中的网卡名称再次重启后生成虚拟网卡，生成的虚拟网卡是一个有独立ip的设备 ，可以使用这个ip和其他主机进行通信

[root@localhost network-scripts]# cp ifcfg-enp0s3 ifcfg-enp0s3\:0
[root@localhost network-scripts]# vim ifcfg-enp0s3\:0
TYPE=Ethernet
BOOTPROTO=static
DEFROUTE=yes
PEERROUTES=yes
IPV4_FAILURE_FATAL=no
NAME=enp0s3:0
UUID=bf8adc16-a9c3-494a-b47e-f572fad38639
DEVICE=enp0s3:0
[root@localhost network-scripts]# ifdown enp0s3 && ifup enp0s3
成功断开设备 'enp0s3'。
成功激活的连接（D-Bus 激活路径：/org/freedesktop/NetworkManager/ActiveConnection/3）
[root@localhost network-scripts]# ifconfig
enp0s3: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet 192.168.1.223 netmask 255.255.255.0 broadcast 192.168.1.255ether 08:00:27:a7:f9:c2 txqueuelen 1000 (Ethernet)RX packets 20698 bytes 21236657 (20.2 MiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 9509 bytes 924400 (902.7 KiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0enp0s3:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet 192.168.1.233 netmask 255.255.255.0 broadcast 192.168.1.255ether 08:00:27:a7:f9:c2 txqueuelen 1000 (Ethernet)

临时修改主机名hostname 主机名 ； 永久修改linux主机名vim /etc/hostname ，重启或source /etc/profile 重新加载系统环境变量文件
DNS配置文件： /etc/resolv.conf这里的DNS文件优先级会低于网卡配置文件中指定的DNS，如果发生重启会被网卡中的DNS配置所覆盖
linux中简单解析文件：/etc/hosts ，修改的解析只在本机生效， 一行内一个ip可以配置多个对应域名

[root@localhost network-scripts]# vim /etc/hosts
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
192.168.1.233 www.bilibili.com www.abc.com www.123.com
[root@localhost network-scripts]# ping www.bilibili.com
PING www.bilibili.com (192.168.1.233) 56(84) bytes of data.
64 bytes from www.bilibili.com (192.168.1.233): icmp_seq=1 ttl=64 time=0.219 ms

firewalld和netfilter工具

关闭selinux工具，selinux默认开启状态，安装某些服务selinux会影响服务正常启动，临时关闭selinux：

[root@localhost network-scripts]# setenforce 0
[root@localhost network-scripts]# getenforce
Disabled

永久关闭selinux

[root@localhost ~]# vim /etc/selinux/config # This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of three two values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

停用firewalld改为使用netfilter工具，需要安装iptables-services的yum包文件

[root@localhost network-scripts]# systemctl disable firewalld
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.
Removed symlink /etc/systemd/system/basic.target.wants/firewalld.service.
[root@localhost network-scripts]# systemctl stop firewalld
[root@localhost network-scripts]# yum install -y iptables-services
已加载插件：fastestmirror
Loading mirror speeds from cached hostfile* base: mirrors.aliyun.com* epel: mirrors.ustc.edu.cn* extras: mirrors.aliyun.com* updates: mirrors.sohu.com
正在解决依赖关系
--> 正在检查事务
---> 软件包 iptables-services.x86_64.0.1.4.21-24.1.el7_5 将被 安装
--> 正在处理依赖关系 iptables = 1.4.21-24.1.el7_5，它被软件包 iptables-services-1.4.21-24.1.el7_5.x86_64 需要
--> 正在检查事务
---> 软件包 iptables.x86_64.0.1.4.21-17.el7 将被 升级
---> 软件包 iptables.x86_64.0.1.4.21-24.1.el7_5 将被 更新
--> 解决依赖关系完成
已安装:iptables-services.x86_64 0:1.4.21-24.1.el7_5                                                                                   作为依赖被升级:iptables.x86_64 0:1.4.21-24.1.el7_5                                                                                            完毕！
[root@localhost network-scripts]# systemctl enable iptables
Created symlink from /etc/systemd/system/basic.target.wants/iptables.service to /usr/lib/systemd/system/iptables.service.
[root@localhost network-scripts]# systemctl start iptables
[root@localhost network-scripts]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target     prot opt in     out     source               destination         51  3496 ACCEPT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            state RELATED,ESTABLISHED0     0 ACCEPT     icmp --  *      *       0.0.0.0/0            0.0.0.0/0           0     0 ACCEPT     all  --  lo     *       0.0.0.0/0            0.0.0.0/0           0     0 ACCEPT     tcp  --  *      *       0.0.0.0/0            0.0.0.0/0            state NEW tcp dpt:228   699 REJECT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-host-prohibitedChain FORWARD (policy ACCEPT 0 packets, 0 bytes)pkts bytes target     prot opt in     out     source               destination         0     0 REJECT     all  --  *      *       0.0.0.0/0            0.0.0.0/0            reject-with icmp-host-prohibitedChain OUTPUT (policy ACCEPT 29 packets, 2876 bytes)pkts bytes target     prot opt in     out     source               destination 

iptables只是netfilter使用的一个工具，只是在使用的时候我们通常称为iptables

netfilter5表5链介绍

filter表：默认的一张表，表中包含INPUT、OUTPUT和FORWARD链
INPUT表示进入本机流量的过滤链，检测端口或来源ip
FORWARD转发链，检查是否为本机流量，非本机流量将会被转发
OUTPUT本机出流量，可禁止到某ip的数据包

nat表：流量数据包转发
PREROUTING数据包进入时更改来源ip
POSTROUTING数据包转发出去是修改目的ip
实现内网服务器和公网服务器之间互相通信，需要在一台出口设备上做端口映射，也就是使用PREROUTING和POSTROUTING链

mangle表：给数据包做标记，如数据类型
raw表：可以实现不追踪某些数据包
security表：加强访问控制的(MAC)网络规则

iptables语法
iptables -nvL查看默认filter表的规则

[root@localhost network-scripts]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         984 83612 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:223211 287K REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibitedChain FORWARD (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibitedChain OUTPUT (policy ACCEPT 772 packets, 175K bytes)pkts bytes target prot opt in out source destination 

iptables -F 清空规则
iptables -t nat -nvL 指定表查看规则

[root@localhost network-scripts]# iptables -t nat -nvL
Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         Chain INPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         Chain OUTPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         Chain POSTROUTING (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination 

iptables -Z 清零计数器
记录通过规则链的数据流累计信息，可以通过记录数判断数据量大小，可以根据数据量发送接收大小来做限制

iptables -A INPUT -s 192.168.1.112 -p tcp --sport 1234 -d 192.168.1.223 --dport 80 -j DROP/REJECT 禁止1.112通过1234端口向223发送数据

[root@localhost network-scripts]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         1142 95952 ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:224450 397K REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibited0 0 DROP tcp -- * * 192.168.1.112 192.168.1.223 tcp spt:1234 dpt:80Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibitedChain OUTPUT (policy ACCEPT 17 packets, 1676 bytes)pkts bytes target prot opt in out source destination

-A 在现有规则后新增一条新规则
-I 在现有规则最前面插入一条规则
-I和-A的区别：匹配规则时会优先从最前面规则进行匹配，如果匹配到规则后就不会再往下匹配了

删除iptables规则
iptables -D INPUT 规则序号

[root@localhost network-scripts]# iptables -D INPUT 6
[root@localhost network-scripts]# iptables -nvL
Chain INPUT (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         1200 100K ACCEPT all -- * * 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED0 0 ACCEPT icmp -- * * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT all -- lo * 0.0.0.0/0 0.0.0.0/0           0 0 ACCEPT tcp -- * * 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:224606 409K REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibitedChain FORWARD (policy ACCEPT 0 packets, 0 bytes)pkts bytes target prot opt in out source destination         0 0 REJECT all -- * * 0.0.0.0/0 0.0.0.0/0 reject-with icmp-host-prohibitedChain OUTPUT (policy ACCEPT 4 packets, 512 bytes)pkts bytes target prot opt in out source destination   

修改链默认的匹配规则，注意如果写入拒绝语句之前，请放行需要使用的端口，否则会造成通信中断(如ssh服务的22端口)
iptables -P INPUT DROP

[root@localhost ~]# iptables -A INPUT -p tcp --dport 22 -j ACCEPT
[root@localhost ~]# iptables -A OUTPUT -p tcp --dport 22 -j ACCEPT
[root@localhost ~]# iptables -A OUTPUT -p tcp --sport 22 -j ACCEPT
[root@localhost ~]# iptables -A INPUT -p tcp --sport 22 -j ACCEPT
[root@localhost ~]# iptables -P INPUT DROP
[root@localhost ~]# iptables -nvL
Chain INPUT (policy DROP 0 packets, 0 bytes)