> For the complete documentation index, see [llms.txt](https://huataihuang.gitbook.io/cloud-atlas-draft/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://huataihuang.gitbook.io/cloud-atlas-draft/devops/gitlab/deploy_key.md).

# 部署使用的ssh key

## `Key has already been taken`

在使用`git clone`命令部署`gitlab`的托管项目文件时，需要首先在项目配置中添加`deploy key`，但是也可能会遇到下列报错

```
Key has already been taken
Fingerprint has already been taken
```

这个问题是因为gitlab中已经有其他项目使用了这个部署公钥，所以无法添加到当前项目。

## 多个ssh密钥对的思路

[Managing Multiple SSH Keys](http://www.robotgoblin.co.uk/blog/2012/07/24/managing-multiple-ssh-keys/)提供了一种解决思路，即如果需要对不同的git仓库使用不同的ssh key时候，可以先创建不同的密钥对：

```bash
mkdir ~/.ssh/fedoraproject
cd ~/.ssh/fedoraproject
ssh-keygen -f id_rsa
```

这样就可以在`~/.ssh/fedoraproject`目录下创建独立的`id_rsa`和`id_rsa.pub`密钥对。

然后配置类似如下

```bash
Host github.com
    User git
    Hostname github.com
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/git/id_rsa
Host fedoraproject.org
    Hostname fedoraproject.org
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/fedoraproject/id_rsa
Host fedorapeople.org
    Hostname fedorapeople.org
    PreferredAuthentications publickey
    IdentityFile ~/.ssh/fedoraproject/id_rsa
```

再使用 `git clone git@fedoraproject.org:example/example_repo.git` 就可以使用指定的密钥来完成。

## 结合`ssh-agent`来使用指定私钥

上述思路中使用了多个密钥对来针对不同域名区别使用密钥，在我们这个案例中，域名是不变的，单是我们也需要使用不同的私钥。

可以参考 [Specify private SSH-key to use when executing shell command with or without Ruby?](http://stackoverflow.com/questions/4565700/specify-private-ssh-key-to-use-when-executing-shell-command-with-or-without-ruby) 使用以下命令

```bash
ssh-agent bash -c 'ssh-add /home/christoffer/ssh_keys/theuser; git clone git@github.com:TheUser/TheProject.git'
```

> 此方法测试可用于`git 1.9`，上述方法解决了对特定项目使用指定密钥对的问题。

另一个建议方法测试没有成功：

```bash
ssh-agent $(ssh-add /home/christoffer/ssh_keys/theuser; git clone git@github.com:TheUser/TheProject.git)
```

## 使用git的`GIT_SSH_COMMAND`来使用指定私钥

参考[How to tell git which private key to use?](http://superuser.com/questions/232373/how-to-tell-git-which-private-key-to-use)，即从`git 2.3.0`开始可以指定环境变量

```bash
GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_example" git clone example
```

这里`-i`也可能被配置文件覆盖，所以可以给予SSH一个空白配置

> `GIT_SSH_COMMAND`环境变量对于低于`git 2.3.0`版本无效

```bash
GIT_SSH_COMMAND="ssh -i ~/.ssh/id_rsa_example -F /dev/null" git clone example
```


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://huataihuang.gitbook.io/cloud-atlas-draft/devops/gitlab/deploy_key.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.