一、基本信息

Ubuntu是linux系统，虽然他是支持界面化操作的，一般用来做服务器用，所以配置ssh可以比较安全的进行访问，也方便在其他地方访问服务器，轻松省事。
Ubuntu系统版本:
使用uname -a指令获取系统版本信息

zero@ubuntu:~$ uname -a
Linux ubuntu 5.15.0-79-generic #86-Ubuntu SMP Mon Jul 10 16:07:21 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

具体信息如下：

• 系统类型： Linux
• 主机名：ubuntu
• 内核版本：5.15.0-79-generic
• 编译时间：#86-Ubuntu SMP Mon Jul 10 16:07:21 UTC 2023
• 硬件架构：x86_64 x86_64 x86_64（处理器架构，操作系统类型，软件环境）
• 操作系统名称：GNU/Linux

二、ssh安装

2.1 查看是否已经安装ssh

直接输入ssh查看

zero@ubuntu:~$ ssh
usage: ssh [-46AaCfGgKkMNnqsTtVvXxYy] [-B bind_interface][-b bind_address] [-c cipher_spec] [-D [bind_address:]port][-E log_file] [-e escape_char] [-F configfile] [-I pkcs11][-i identity_file] [-J [user@]host[:port]] [-L address][-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port][-Q query_option] [-R address] [-S ctl_path] [-W host:port][-w local_tun[:remote_tun]] destination [command [argument ...]]

有具体的信息就是已经安装了。

2.2 安装ssh

可以使用如下指令安装ssh

sudo apt-get install openssh-server

一般服务器是被访问的，所以只要安装openssh-server即可，如果要安装客户端，将安装的内容改成openssh-client即可。

2.3 查看ssh安装状态

安装完成后重新查看ssh安装状态
使用netstat查看状态

zero@ubuntu:~$ sudo netstat -tlnp | grep sshd
[sudo] password for zero:
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2714/sshd: /usr/sbi
tcp6       0      0 :::22                   :::*                    LISTEN      2714/sshd: /usr/sbi

使用systemctl查看状态

zero@ubuntu:~$ sudo systemctl status ssh
● ssh.service - OpenBSD Secure Shell serverLoaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)Active: active (running) since Sat 2023-08-26 15:01:13 UTC; 13min agoDocs: man:sshd(8)man:sshd_config(5)Main PID: 2714 (sshd)Tasks: 1 (limit: 4514)Memory: 4.0MCPU: 33msCGroup: /system.slice/ssh.service└─2714 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"Aug 26 15:01:13 ubuntu systemd[1]: Starting OpenBSD Secure Shell server...
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on 0.0.0.0 port 22.
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on :: port 22.
Aug 26 15:01:13 ubuntu systemd[1]: Started OpenBSD Secure Shell server.
Aug 26 15:11:26 ubuntu sshd[2899]: Accepted password for zero from 192.168.159.1 port 51604 ssh2
Aug 26 15:11:26 ubuntu sshd[2899]: pam_unix(sshd:session): session opened for user zero(uid=1000) by (uid=0)

三、启动、停止，及开机自启动

3.1 启动ssh

zero@ubuntu:~$ sudo systemctl start ssh		#启动ssh服务
zero@ubuntu:~$ sudo systemctl status sshd	#查询状态
Unit sshd.service could not be found.
zero@ubuntu:~$ sudo systemctl status ssh
● ssh.service - OpenBSD Secure Shell serverLoaded: loaded (/lib/systemd/system/ssh.service; disabled; vendor preset: enabled)Active: active (running) since Sat 2023-08-26 15:01:13 UTC; 27min agoDocs: man:sshd(8)man:sshd_config(5)Main PID: 2714 (sshd)Tasks: 1 (limit: 4514)Memory: 4.0MCPU: 33msCGroup: /system.slice/ssh.service└─2714 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"Aug 26 15:01:13 ubuntu systemd[1]: Starting OpenBSD Secure Shell server...
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on 0.0.0.0 port 22.
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on :: port 22.
Aug 26 15:01:13 ubuntu systemd[1]: Started OpenBSD Secure Shell server.
Aug 26 15:11:26 ubuntu sshd[2899]: Accepted password for zero from 192.168.159.1 port 51604 ssh2
Aug 26 15:11:26 ubuntu sshd[2899]: pam_unix(sshd:session): session opened for user zero(uid=1000) by (uid=0)
zero@ubuntu:~$ sudo netstat -tlnp | grep sshd	#查询状态
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      2714/sshd: /usr/sbi
tcp6       0      0 :::22                   :::*                    LISTEN      2714/sshd: /usr/sbi

3.2 关闭ssh

zero@ubuntu:~$ sudo systemctl stop ssh				#关闭ssh服务
zero@ubuntu:~$ sudo netstat -tlnp | grep sshd		#关闭后查询不到网络状态
zero@ubuntu:~$ sudo systemctl status ssh			#ssh状态已关闭
○ ssh.service - OpenBSD Secure Shell serverLoaded: loaded (/lib/systemd/system/ssh.service; disabled; vendor preset: enabled)Active: inactive (dead) since Sat 2023-08-26 15:34:05 UTC; 11s agoDocs: man:sshd(8)man:sshd_config(5)Process: 2714 ExecStart=/usr/sbin/sshd -D $SSHD_OPTS (code=exited, status=0/SUCCESS)Main PID: 2714 (code=exited, status=0/SUCCESS)CPU: 35msAug 26 15:01:13 ubuntu systemd[1]: Starting OpenBSD Secure Shell server...
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on 0.0.0.0 port 22.
Aug 26 15:01:13 ubuntu sshd[2714]: Server listening on :: port 22.
Aug 26 15:01:13 ubuntu systemd[1]: Started OpenBSD Secure Shell server.
Aug 26 15:11:26 ubuntu sshd[2899]: Accepted password for zero from 192.168.159.1 port 51604 ssh2
Aug 26 15:11:26 ubuntu sshd[2899]: pam_unix(sshd:session): session opened for user zero(uid=1000) by (uid=0)
Aug 26 15:34:05 ubuntu systemd[1]: Stopping OpenBSD Secure Shell server...
Aug 26 15:34:05 ubuntu systemd[1]: ssh.service: Deactivated successfully.
Aug 26 15:34:05 ubuntu systemd[1]: Stopped OpenBSD Secure Shell server.

3.3 使用systemctl设置ssh服务自启动

zero@ubuntu:~$ sudo systemctl enable ssh
Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable ssh

设置完成之后重启即可

3.4 使用systemctl关闭ssh开机启动

zero@ubuntu:~$ sudo systemctl disable ssh
Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install disable ssh
Removed /etc/systemd/system/multi-user.target.wants/ssh.service.
Removed /etc/systemd/system/sshd.service.

四、配置通过密钥进行免密访问

部分操作说明可参考Windows下配置SSH实现免密访问和远程端口转发，本文直接进行操作。

4.1 生成密钥

zero@ubuntu:~$ sudo ssh-keygen			#此处直接使用默认设置生成rsa的密钥
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa):	//不修改路径
Enter passphrase (empty for no passphrase):			#不设置密码，实际使用根据自己需要设置密码会比较安全
Enter same passphrase again:
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:
SHA256:elLfv9r5e4RLOSKnee6oJPBGmS6YGm3WcAuvXVAxBtg root@ubuntu
The key's randomart image is:
+---[RSA 3072]----+
|   o..+          |
|  . E. o         |
|      .          |
|     . o         |
|  o + + S      o |
| . O B o ...o = .|
|. * = O o .=.o + |
| = o + =  o..o...|
|. . .   ...++.=++|
+----[SHA256]-----+

注： 若要配置git访问服务器，此处密钥对可使用rsa格式的，git for windows默认识别rsa密钥。

4.2 通过ssh-agent管理私钥

zero@ubuntu:~$ ssh-agent			#启动服务
SSH_AUTH_SOCK=/tmp/ssh-XXXXXXjkoDta/agent.3455; export SSH_AUTH_SOCK;
SSH_AGENT_PID=3456; export SSH_AGENT_PID;
echo Agent pid 3456;zero@ubuntu:~$ ssh-add /root/.ssh/id_rsa	# 没有使用agent启动bash直接调用ssh-add添加私钥会报错
Could not open a connection to your authentication agent.	zero@ubuntu:~$ sudo ssh-agent bash --login -i		# 使用ssh-agent启动bash，注意需要添加sudo，添加root的密钥需要使用root权限。root@ubuntu:/home/zero# ssh-add /root/.ssh/id_rsa		#将密钥添加到agent中
Identity added: /root/.ssh/id_rsa (root@ubuntu)
root@ubuntu:/home/zero# exit		# 退出当前bash
logout
zero@ubuntu:~$

4.3 管理公钥

服务器管理公钥，可以直接添加公钥文件中

zero@ubuntu:~$ cat /root/.ssh/id_ras.pub >> authorized_keys			# 直接拷贝汇报错，当我们要操作的公钥在root文件夹下时就需要root权限
cat: /root/.ssh/id_ras.pub: Permission deniedzero@ubuntu:~$ sudo cat /root/.ssh/id_rsa.pub >> authorized_keys			# 添加sudo使用root权限操作
zero@ubuntu:~$			# 操作成功没有错误提示

4.4 通过scp将公钥拷贝到服务器

需要将公钥拷贝到要访问的服务器中。

PS C:\WINDOWS\system32> scp C:\Users\LJM\.ssh\id_rsa.pub zero@192.168.159.129:.ssh/id_rsa_git.pub
zero@192.168.159.129's password:
id_rsa.pub                                                                            100%  567   558.8KB/s   00:00
PS C:\WINDOWS\system32>

4.5 将公钥添加到公钥管理文件中

切换到.ssh文件夹中，然后将公钥添加到公钥管理文件中。

zero@ubuntu:~/.ssh$ ll
total 24
drwx------ 2 zero zero 4096 Aug 26 17:25 ./
drwxr-x--- 4 zero zero 4096 Aug 26 16:13 ../
-rw------- 1 zero zero  567 Aug 26 17:28 authorized_keys
-rw-rw-r-- 1 zero zero 2602 Aug 26 16:57 id_rsa_git
-rw-rw-r-- 1 zero zero  567 Aug 26 17:25 id_rsa_git.pub
-rw-r--r-- 1 root root  565 Aug 26 16:43 id_rsa.pub
zero@ubuntu:~/.ssh$ cat id_rsa_git.pub >> authorized_keys

4.6 享受ssh免密链接服务器

公钥和私钥添加管理后，对应的文件即可删除了。然后客户端就可以通过ssh免密访问服务器。

通常一般要访问的客户端保存私钥，服务端保存公钥。