为什么SSH从命令行执行时从crontab中，但succedes不成？ [英] Why ssh fails from crontab but succedes when executed from a command line?

问题描述

我有一个bash脚本，做的ssh到远程计算机并执行命令存在，如：

I have a bash script that does ssh to a remote machine and executes a command there, like:

ssh -nxv user@remotehost echo "hello world"

当我从它工作正常的命令行中执行命令，但被作为crontab中的一部分执行时失败（错误code = 255 - 无法建立SSH连接）。联系方式：

When I execute the command from a command line it works fine, but it fails when is being executed as a part of crontab (errorcode=255 - cannot establish SSH connection). Details:

...
Waiting for server public key.
Received server public key and host key.
Host 'remotehost' is known and matches the XXX host key.
...
Remote: Your host key cannot be verified: unknown or invalid host key.
Server refused our host key.
Trying XXX authentication with key '...'
Server refused our key.
...

在本地执行，我作为一个根，工程的crontab作为root为好。
从crontab中和命令行执行'身份证'给出完全相同的结果：

When executing locally I'm acting as a root, crontab works as root as well. Executing 'id' from crontab and command line gives exactly the same result:

$ id
> uid=0(root) gid=0(root) groups=0(root),...

我做的ssh一些本地机器的机器运行的crond。我有SSH密钥和证书ssh到crond的机器和任何其他机器，该脚本连接到。

I do ssh from some local machine to the machine running crond. I have ssh key and credentials to ssh to crond machine and any other machine that the scripts connects to.

PS。请不要问/抱怨/评论说，执行任何以root身份是坏/错误的/ etc - 它不是这个问题的目的

PS. Please do not ask/complain/comment that executing anything as root is bad/wrong/etc - it is not the purpose of this question.

推荐答案

我猜测，通常当你从本地机器的ssh到本机运行crond的，你的私钥是ssh-agent的加载，并转发了连接。所以，当你在命令行中执行命令，它找到的ssh-agent你的私钥，并使用它来登录到远程机器。

I am guessing that normally when you ssh from your local machine to the machine running crond, your private key is loaded in ssh-agent and forwarded over the connection. So when you execute the command from the command line, it finds your private key in ssh-agent and uses it to log in to the remote machine.

在crond的执行命令，它没有进入的ssh-agent，所以不能用你的私钥。

When crond executes the command, it does not have access to ssh-agent, so cannot use your private key.

您必须创建在机器运行的crond根新的私钥，它的公共部分复制到相应的的authorized_keys 远程计算机上的文件你想crond的登录。

You will have to create a new private key for root on the machine running crond, and copy the public part of it to the appropriate authorized_keys file on the remote machine that you want crond to log in to.

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