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5 SSH alias examples in Linux
======
[![][1]][1]
As a Linux user, we use[ ssh command][2] to log in to remote machines. The more you use ssh command, the more time you are wasting in typing some significant commands. We can use either [alias defined in your .bashrc file][3] or functions to minimize the time you spend on CLI. But this is not a better solution. The better solution is to use **SSH-alias** in ssh config file.
A couple of examples where we can better the ssh commands we use.
Connecting to ssh to AWS instance is a pain. Just to type below command, every time is complete waste your time as well.
to
```
ssh aws1
```
Connecting to a system when debugging.
to
```
ssh xyz
```
In this post, we will see how to achieve shorting of your ssh commands without using bash alias or functions. The main advantage of ssh alias is that all your ssh command shortcuts are stored in a single file and easy to maintain. The other advantage is we can use same alias **for both SSH and SCP commands alike**.
Before we jump into actual configurations, we should know difference between /etc/ssh/ssh_config, /etc/ssh/sshd_config, and ~/.ssh/config files. Below is the explanation for these files.
## Difference between /etc/ssh/ssh_config and ~/.ssh/config
System-level SSH configurations are stored in /etc/ssh/ssh_config. Whereas user-level ssh configurations are stored in ~/.ssh/config file.
## Difference between /etc/ssh/ssh_config and /etc/ssh/sshd_config
System-level SSH configurations are stored in /etc/ssh/ssh_config. Whereas system level SSH server configurations are stored in /etc/ssh/sshd_config file.
## **Syntax for configuration in ~/.ssh/config file**
Syntax for ~/.ssh/config file content.
```
config val
config val1 val2
```
**Example1:** Create SSH alias for a host(www.linuxnix.com)
Edit file ~/.ssh/config with following content
```
Host tlj
User root
HostName 18.197.176.13
port 22
```
Save the file
The above ssh alias uses
1. **tlj as an alias name**
2. **root as a user who will log in**
3. **18.197.176.13 as hostname IP address**
4. **22 as a port to access SSH service.**
Output:
```
sanne@Surendras-MacBook-Pro:~ > ssh tlj
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sat Oct 14 01:00:43 2017 from 20.244.25.231
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
```
**Example2:** Using ssh key to login to the system without using password using **IdentityFile**.
Example:
```
Host aws
User ec2-users
HostName ec2-54-200-184-202.us-west-2.compute.amazonaws.com
IdentityFile ~/Downloads/surendra.pem
port 22
```
**Example3:** Use a different alias for the same host. In below example, we use **tlj, linuxnix, linuxnix.com** for same IP/hostname 18.197.176.13.
~/.ssh/config file content
```
Host tlj linuxnix linuxnix.com
User root
HostName 18.197.176.13
port 22
```
**Output:**
```
sanne@Surendras-MacBook-Pro:~ > ssh tlj
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sat Oct 14 01:00:43 2017 from 220.244.205.231
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
sanne@Surendras-MacBook-Pro:~ > ssh linuxnix.com
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
```
```
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sun Oct 15 20:31:08 2017 from 1.129.110.13
root@linuxnix:~# exit
logout
Connection to 138.197.176.103 closed.
[6571] sanne@Surendras-MacBook-Pro:~ > ssh linuxnix
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sun Oct 15 20:31:20 2017 from 1.129.110.13
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
```
**Example4:** Copy a file to remote system using same SSH alias
Syntax:
```
**scp <filename> <ssh_alias>:<location>**
```
Example:
```
sanne@Surendras-MacBook-Pro:~ > scp abc.txt tlj:/tmp
abc.txt 100% 12KB 11.7KB/s 00:01
sanne@Surendras-MacBook-Pro:~ >
```
As we already set ssh host as an alias, using SCP is a breeze as both ssh and SCP use almost same syntax and options.
To do scp a file from local machine to remote one use below.
**Examaple5:** Resolve SSH timeout issues in Linux. By default, your ssh logins are timed out if you don 't activily use the terminial.
[SSH timeouts][5] are one more pain where you have to re-login to a remote machine after a certain time. We can set SSH time out right in side your ~/.ssh/config file to make your session active for whatever time you want. To achieve this we will use two SSH options for keeping the session alive. One ServerAliveInterval keeps your session live for number of seconds and ServerAliveCountMax will initial session after session for a given number.
```
**ServerAliveInterval A**
**ServerAliveCountMax B**
```
**Example:**
```
Host tlj linuxnix linuxnix.com
User root
HostName 18.197.176.13
port 22
ServerAliveInterval 60**
ServerAliveCountMax 30
```
We will see some other exiting howto in our next post. Keep visiting linuxnix.com.
--------------------------------------------------------------------------------
via: https://www.linuxnix.com/5-ssh-alias-examples-using-ssh-config-file/
作者：[Surendra Anne;Max Ntshinga;Otto Adelfang;Uchechukwu Okeke][a]
译者：[译者ID](https://github.com/译者ID)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:https://www.linuxnix.com
[1]:https://www.linuxnix.com/wp-content/uploads/2017/10/SSH-alias-1.png
[2]:https://www.linuxnix.com/ssh-access-remote-linux-server/
[3]:https://www.linuxnix.com/linux-alias-command-explained-with-examples/
[4]:/cdn-cgi/l/email-protection
[5]:https://www.linuxnix.com/how-to-auto-logout/

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Linux 中的 5 个 SSH 别名例子
======
[![][1]][1]
作为一个 Linux 用户，我们常用[ ssh 命令][2] 来登入远程机器。ssh 命令你用得越多，你在键入一些重要的命令上花的时间也越多。我们可以用 [定义在你的 .bashrc 文件里的别名][3] 或函数来大幅度缩减花在命令行界面（CLI）的时间。但这不是最佳解决之道。最佳办法是在 ssh 配置文件中使用 **SSH-别名** 。
这里是我们能把 ssh 命令用得更好的几个例子。
ssh 到 AWS（译注：Amazon Web Services，亚马逊公司旗下云计算服务平台）实例的连接是一种痛。仅仅输入以下命令，每次也完全是浪费你时间。
```
ssh -p 3000 -i /home/surendra/mysshkey.pem ec2-user@ec2-54-20-184-202.us-west-2.compute.amazonaws.com
```
缩短到
```
ssh aws1
```
调试时连接到系统。
```
ssh -vvv the_good_user@red1.taggle.abc.com.au
```
缩短到
```
ssh xyz
```
在本篇中，我们将看到如何不使用 bash 别名或函数实现 ssh 命令的缩短。ssh 别名的主要优点是所有的 ssh 命令快捷方式都存储在一个单一文件,如此就易于维护。其他优点是 **对于类似于 SSH 和 SCP 的命令** 我们能用相同的别名。
在我们进入实际配置之前，我们应该知道 /etc/ssh/ssh_config、/etc/ssh/sshd_config 和 ~/.ssh/config 文件三者的区别。以下是对这些文件的解释。
## /etc/ssh/ssh_config 和 ~/.ssh/config 间的区别
系统级别的 SSH 配置项存放在 /etc/ssh/ssh_config，而用户级别的 ssh 配置项存放在 ~/.ssh/config 文件中。
## /etc/ssh/ssh_config 和 /etc/ssh/sshd_config 间的区别
系统级别的 SSH 配置项是在 /etc/ssh/ssh_config 文件中，而系统级别的 SSH 服务端配置项存放在 /etc/ssh/sshd_config 文件。
## **在 ~/.ssh/config 文件里配置项的语法**
~/.ssh/config 文件内容的语法。
```
配置项 值
配置项 值1 值2
```
**例 1：** 创建主机（www.linuxnix.com）的 SSH 别名
编辑 ~/.ssh/config 文件写入以下内容
```
Host tlj
User root
HostName 18.197.176.13
port 22
```
保存此文件
以上 ssh 别名用了
1. **tlj 作为一个别名的名称**
2. **root 作为将要登入的用户**
3. **18.197.176.13 作为主机的 IP 地址**
4. **22 作为访问 SSH 服务的端口。**
输出：
```
sanne@Surendras-MacBook-Pro:~ > ssh tlj
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sat Oct 14 01:00:43 2017 from 20.244.25.231
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
```
**例 2：** 不用密码用 ssh 密钥登到系统要用 **IdentityFile** 。
例：
```
Host aws
User ec2-users
HostName ec2-54-200-184-202.us-west-2.compute.amazonaws.com
IdentityFile ~/Downloads/surendra.pem
port 22
```
**例 3：** 对同一主机使用不同的别名。在下例中，我们对同一 IP/主机 18.197.176.13 用了 **tlj, linuxnix, linuxnix.com** 三个别名。
~/.ssh/config 文件内容
```
Host tlj linuxnix linuxnix.com
User root
HostName 18.197.176.13
port 22
```
**输出：**
```
sanne@Surendras-MacBook-Pro:~ > ssh tlj
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sat Oct 14 01:00:43 2017 from 220.244.205.231
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
sanne@Surendras-MacBook-Pro:~ > ssh linuxnix.com
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
```
```
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sun Oct 15 20:31:08 2017 from 1.129.110.13
root@linuxnix:~# exit
logout
Connection to 138.197.176.103 closed.
[6571] sanne@Surendras-MacBook-Pro:~ > ssh linuxnix
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-93-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
Get cloud support with Ubuntu Advantage Cloud Guest:
http://www.ubuntu.com/business/services/cloud
Last login: Sun Oct 15 20:31:20 2017 from 1.129.110.13
root@linuxnix:~# exit
logout
Connection to 18.197.176.13 closed.
```
**例 4：** 用相同的 SSH 别名复制文件到远程系统
语法：
```
**scp <文件名> <ssh_别名>:<位置>**
```
例子：
```
sanne@Surendras-MacBook-Pro:~ > scp abc.txt tlj:/tmp
abc.txt 100% 12KB 11.7KB/s 00:01
sanne@Surendras-MacBook-Pro:~ >
```
若我们已经将 ssh 主机设置好一个别名，由于 ssh 和 SCP 两者用几乎相同的语法和选项，SCP 用起来就轻而易举
请在下面尝试从本机 scp 一个文件到远程机器。
**例 5：** 解决 Linux中的 SSH 超时问题。默认情况，如果你不积极地使用终端，你的 ssh 登入就会超时。
[SSH 超时问题][5] 是一个更痛的点意味着你在一段时间后不得不重新登入到远程机器。我们能在 ~/.ssh/config 文件里边恰当地设置 SSH 超时时间来使你的会话不管在什么时间总是激活的。我们将用 2 个能保持会话存活的 SSH 选项来实现这一目的。之一是 ServerAliveInterval 保持你会话存活的秒数和 ServerAliveCountMax 在（经历了一个）给定数值的会话之后初始化会话。
```
**ServerAliveInterval A**
**ServerAliveCountMax B**
```
**例：**
```
Host tlj linuxnix linuxnix.com
User root
HostName 18.197.176.13
port 22
ServerAliveInterval 60**
ServerAliveCountMax 30
```
在下篇中我们将会看到一些其他的退出方式。请保持访问 linuxnix.com。
--------------------------------------------------------------------------------
via: https://www.linuxnix.com/5-ssh-alias-examples-using-ssh-config-file/
作者：[Surendra Anne;Max Ntshinga;Otto Adelfang;Uchechukwu Okeke][a]
译者：[ch-cn](https://github.com/ch-cn)
校对：[校对者ID](https://github.com/校对者ID)
本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
[a]:https://www.linuxnix.com
[1]:https://www.linuxnix.com/wp-content/uploads/2017/10/SSH-alias-1.png
[2]:https://www.linuxnix.com/ssh-access-remote-linux-server/
[3]:https://www.linuxnix.com/linux-alias-command-explained-with-examples/
[4]:/cdn-cgi/l/email-protection
[5]:https://www.linuxnix.com/how-to-auto-logout/