Ubuntu18.04.5不重启的情况下更改主机名并在集群之间能够相互映射

问题记录：想在不重启Ubuntu18.04.5的情况下更改主机名并在集群之间能够相互映射
（1）查看Ubuntu的版本

cat /proc/version	linux内核版本号	gcc编译器版本	Ubuntu版本号
	Linux version 5.4.0-42-generic ([email protected]) 
	(gcc version 7.5.0 (Ubuntu 7.5.0-3ubuntu1~18.04)) #46~18.04.1-Ubuntu SMP Fri Jul 10 07:21:24 UTC 2020	

uname -a		显示linux的内核版本和系统是多少位的：X86_64代表系统是64位的
	Linux seibigdata-virtual-machine 5.4.0-42-generic #46~18.04.1-Ubuntu SMP Fri Jul 10 07:21:24 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

lsb_release -a	
	No LSB modules are available.	//类别是ubuntu
	Distributor ID:	Ubuntu
	Description:	Ubuntu 18.04.5 LTS //发行日期或者是发行版本号
	Release:	18.04
	Codename:	bionic		//ubuntu的代号名称

（2）修改主机名

hostnamectl
之前的主机名
1）sudo hostnamectl set-hostname master
master
2）sudo /etc/hosts       # 修改之前的主机名为master，并在后面添加其他和自己的主机ip映射
127.0.0.1	localhost
127.0.1.1	master

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.27.102.191 master
172.27.102.200 slave1
172.27.102.201 slave2
172.27.102.202 slave3


3）ls -l /etc/cloud/cloud.cfg
如果运行上面的语句，显示没有目录，我们修改主机名就已经成功了，否则的话运行4）修改preserve_hostname

4）sudo nano /etc/cloud/cloud.cfg  （该步骤可以没有）
preserve_hostname并将值从false更改为true


hostnamectl
master

依次改完其他三台的主机名上操作，改为slave1、slave2、slave3
5）ping slave1         # 可以ping通，映射成功
PING slave1 (172.27.102.200) 56(84) bytes of data.
64 bytes from slave1 (172.27.102.200): icmp_seq=1 ttl=64 time=0.612 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=2 ttl=64 time=0.380 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=3 ttl=64 time=0.374 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=4 ttl=64 time=0.401 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=5 ttl=64 time=0.337 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=6 ttl=64 time=0.260 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=7 ttl=64 time=0.324 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=8 ttl=64 time=0.377 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=9 ttl=64 time=0.306 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=10 ttl=64 time=0.292 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=11 ttl=64 time=0.297 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=12 ttl=64 time=0.361 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=13 ttl=64 time=0.383 ms

64 bytes from slave1 (172.27.102.200): icmp_seq=14 ttl=64 time=0.390 ms
64 bytes from slave1 (172.27.102.200): icmp_seq=15 ttl=64 time=0.364 ms