systemd
系统的初始化程序，系统开始额第一个进程，pid为1
systemctl 命令
systemctl list-units 列出当前系统服务的状态
systemctl list-unit-files 列出服务的开机状态
systemctl status sshd 查看指定服务的状态
systemctl stop sshd 关闭指定服务
systemctl start sshd 开启指定服务
systemctl restart sshd 重新启指制定服务
systemctl enable sshd 设定指定服务开机开启
systemctl disable sshd 设定指定服务开机关闭
systemctl reload sshd 使制定服务重新加载配置
systemctl list-dependences sshd 查看制定服务的依赖关系
sysytemctl mask sshd 冻结指定服务
sysytemcrl unmask sshd 启用服务
systemctl set-defult multi-user.target 开机不开启图形
systemctl set-defult graphical.target 开机开启图形
服务状态
systemctl status serviceName
loaded 系统服务已经初始化完成，加载过配置
active（running） 正有一个或多个程序正在系统中执行
vsftpd就是这种模式
active（exited） 仅执行一次就正常结束的服务
目前并没有任何程序在系统中执行
active（waiting） 正在执行当中
不过还在等待其他事件才能继续处理
inactive 服务关闭
enabled 服务开机启动
disabled 服务开机不自启
static 服务开机启动项不可被管理
openssh-server
openssh-server
功能：让远程主机可以通过网络访问ssh服务，开始一个安全的shell
客户端连接方式
ssh远程主机用户@远程主机ip
实验：用desktop机远程控制server机
[root@localhost .ssh]# ssh root@172.25.28.11 连接远程主机用户
The authenticity of host '172.25.28.11 (172.25.28.11)' can't be established.
ECDSA key fingerprint is eb:24:0e:07:96:26:b1:04:c2:37:0c:78:2d:bc:b0:08.
Are you sure you want to continue connecting (yes/no)? yes 连接陌生主机需要建立认证关系
Warning: Permanently added '172.25.28.11' (ECDSA) to the list of known hosts.
root@172.25.28.11's password: 远程主机用户密码
[root@localhost ~]# 连接成功
*在desktop机的.ssh/下会生成known_hosts,里面记录你访问过客户端的公钥。删除（>known_hosts）后，再次访问该客户端，需重新建立认证关系。
ssh 远程主机用户名@远程主机ip -X 调用运城主机图形工具
在server机打开
[root@localhost .ssh]# vim /etc/motd
输入内容
在desktop机远程控制server机时，就会出现该输入内容。
[root@localhost .ssh]# ssh root@172.25.28.11
root@172.25.28.11's password:
Last login: Sun Nov 6 22:34:14 2016 from 172.25.28.10
输入的内容
ssh-keygen （用此种方式验证登陆）
在server机中
生成公钥私钥
[root@localhost .ssh]# ssh-keygen 生成公钥私钥工具
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): [enter] 加密字符保存文件（建议使用默认）
Enter passphrase (empty for no passphrase): [enter] 密码钥匙，必须>4个字符（也可以输入空格）
Enter same passphrase again: [enter] 确认密码
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
d5:e5:dc:98:ed:d6:fe:c5:4e:bc:c7:25:a6:21:f4:90 root@localhost
The key's randomart image is:
+--[ RSA 2048]----+
| . |
| . + = |
| ... = o|
| .E ..|
| S. o +|
| . o o=.|
| . + oB|
| . o*|
| .+|
+-----------------+
[root@localhost .ssh]# ls/root/.ssh/
id_rsa 私钥。就是钥匙
id_rsa.pub 公钥。就是锁
添加key认证方式
[root@localhost .ssh]# ssh-copy-id -i /root/.ssh/id_rsa.pub root@172.25.28.11
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
root@172.25.28.11's password:
Permission denied, please try again.
root@172.25.28.11's password:
Number of key(s) added: 1
Now try logging into the machine, with: "ssh 'root@172.25.28.11'"
and check to make sure that only the key(s) you wanted were added.
[root@localhost .ssh]# ls
authorized_keys id_rsa id_rsa.pub known_hosts
[root@localhost .ssh]#
ssh-copy-id 添加key认证方式的工具
-i 指定加密key文件
/root/.ssh/id_rsa.pub 加密key
root 加密用户为root
172.25.28.11 被加密主机ip
分发钥匙给client主机
[root@localhost ~]# scp /root/.ssh/id_rsa root@172.25.28.10:/root/.ssh/
root@172.25.28.10's password:
id_rsa 100% 1675 1.6KB/s 00:00
测试
用desktop机
[root@localhost ~]# ssh root@172.25.28.11 通过id_sra直接连接不需要输入密码（如果在生成钥匙中）
Last login: Mon Nov 7 00:32:45 2016 from 172.25.28.10
[root@localhost ~]# su - student
[student@localhost ~]$ ssh @172.25.28.11
usage: ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec]
[-D [bind_address:]port] [-E log_file] [-e escape_char]
[-F configfile] [-I pkcs11] [-i identity_file]
[-L [bind_address:]port:host:hostport] [-Q protocol_feature]
[-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port]
[-R [bind_address:]port:host:hostport] [-S ctl_path]
[-W host:port] [-w local_tun[:remote_tun]]
[user@]hostname [command]
sshd服务的简单配置
vim /etc/ssh/sshd_config sshd服务的配置文件
48 PermitRootLogin yes|no 是否允许root用户通过sshd的认证
78 PasswordAuthentication yes|no 开启或关闭用户密码认证
AllowUsers student westos 用户白名单，只允许在名单中出现的用户使用sshd服务
systemctl restart sshd 从新加载配置
改ip
ifconfig eth0 172.25.28.200 netmask 255.255.255.0 临时更改ip
nm-connection-editor 图形界面改ip（永久的）
systemctl restart network 重启网络
nmtui 文本界面改ip（永久的）
systemctl restart network 重启
