SSH远程执行脚本报错command not found和环境变量问题

Bertha 。 2023-07-11 11:21 4阅读 0赞

### 文章目录 ###

*  SSH远程执行脚本报错command not found和环境变量问题
 *   *  SSH远程执行脚本报错
     *  login shell和non-login shell
     *  Linux的环境配置文件
     *  login shell和non-login shell读取的环境变量配置文件
     *  解决non-login shell的环境配置问题
     *  Linux Shell Sebang的注意事项
     *  参考文档

# SSH远程执行脚本报错command not found和环境变量问题 #

## SSH远程执行脚本报错 ##

SSH远程执行脚本报错"command not found"，且环境变量不生效，执行`env`命令后发现打印出来的环境变量少了很多。

原因是之前将环境变量配置在了`/etc/profile`中，但是SSH远程执行脚本时实际上执行的是non-login shell，而non-login shell不会读取`/etc/profile`配置文件。

## login shell和non-login shell ##

简单来说，用SSH客户端（比如Putty）登陆Linux系统时，要求输入用户名/密码登录或根据SSH key登录时，就是login shell。

而在A机器上再用SSH免密码登录B机器，在B机器上执行Shell脚本，就是non-login shell。

ssh -o StrictHostKeyChecking=no -l root ${server} "~/test.sh"

用Ansible在目标机器上远程执行Shell脚本时，也是non-login shell，因为Ansible是基于SSH的。

## Linux的环境配置文件 ##

运行`man bash`可以查看环境配置文件的说明：

CentOS 7上的示例：

/etc/profile
           The systemwide initialization file, executed for login shells
    /etc/bash.bash_logout
           The systemwide login shell cleanup file, executed when a login shell exits
    ~/.bash_profile
           The personal initialization file, executed for login shells
    ~/.bashrc
           The individual per-interactive-shell startup file
    ~/.bash_logout
           The individual login shell cleanup file, executed when a login shell exits
    ~/.inputrc
            Individual readline initialization file

补充说明：

> Classically, `~/.profile` is used by Bourne Shell, and is probably supported by Bash as a legacy measure. Again, `~/.login` and `~/.cshrc` were used by C Shell - I’m not sure that Bash uses them at all.
> 
> The `~/.bash_profile` would be used once, at login. The `~/.bashrc` script is read every time a shell is started. This is analogous to `/.cshrc` for C Shell.
> 
> One consequence is that stuff in `~/.bashrc` should be as lightweight (minimal) as possible to reduce the overhead when starting a non-login shell.
> 
> I believe the `~/.environment` file is a compatibility file for Korn Shell.

小结：

*  `/etc` 下的是系统环境配置，对所有用户有效，但是`/etc/profile`只对login shell有效，而`/etc/bashrc`对login shell和non-login shell都有效。
 *  `~`下的是当前用户环境配置，当前用户环境配置会继承`/etc`系统环境配置。

## login shell和non-login shell读取的环境变量配置文件 ##

*  `/etc/profile`
 *  `~/.bash_profile`
 *  `~/.profile`
 *  `~/.bashrc`
 *  `/etc/bashrc`

注意：`~/.bash_profile`中已经引入了`~/.bashrc`，而`~/.bashrc`引入了`/etc/bashrc`，因此login shell可以读取到`~/.bashrc`和`/etc/bashrc`的配置。

# Get the aliases and functions
    if [ -f ~/.bashrc ]; then
            . ~/.bashrc
    fi

non-login shell读取环境变量配置文件：

*  `/etc/bashrc`
 *  `~/.bashrc`

## 解决non-login shell的环境配置问题 ##

方法一：

将login-shell和non-login shell都需要的环境配置放在`~/.bashrc`中，其它配置放在`~/.bash_profile`中。

方法二：

如果环境配置只放在`~/.bash_profile`中，需要执行non-login shell时先`source ~/.bash_profile`再执行命令。

## Linux Shell Sebang的注意事项 ##

虽然大多数情况下，在Shell开头用`#!/usr/bin/env bash`比`#!/bin/bash`更有通用性，但是在通过SSH远程执行Shell脚本时，Shell开头要用`#!/bin/bash`。

## 参考文档 ##

*  [https://unix.stackexchange.com/questions/38175/difference-between-login-shell-and-non-login-shell][https_unix.stackexchange.com_questions_38175_difference-between-login-shell-and-non-login-shell]
 *  [https://stackoverflow.com/questions/415403/whats-the-difference-between-bashrc-bash-profile-and-environment][https_stackoverflow.com_questions_415403_whats-the-difference-between-bashrc-bash-profile-and-environment]
 *  [https://www.thegeekstuff.com/2008/10/execution-sequence-for-bash\_profile-bashrc-bash\_login-profile-and-bash\_logout/][https_www.thegeekstuff.com_2008_10_execution-sequence-for-bash_profile-bashrc-bash_login-profile-and-bash_logout]
 *  [关于ansible远程执行的环境变量问题（login shell & nonlogin shelll）][ansible_login shell _ nonlogin shelll]
 *  [ssh连接远程主机执行脚本的环境变量问题][ssh]

[https_unix.stackexchange.com_questions_38175_difference-between-login-shell-and-non-login-shell]: https://unix.stackexchange.com/questions/38175/difference-between-login-shell-and-non-login-shell
[https_stackoverflow.com_questions_415403_whats-the-difference-between-bashrc-bash-profile-and-environment]: https://stackoverflow.com/questions/415403/whats-the-difference-between-bashrc-bash-profile-and-environment
[https_www.thegeekstuff.com_2008_10_execution-sequence-for-bash_profile-bashrc-bash_login-profile-and-bash_logout]: https://www.thegeekstuff.com/2008/10/execution-sequence-for-bash_profile-bashrc-bash_login-profile-and-bash_logout/
[ansible_login shell _ nonlogin shelll]: https://my.oschina.net/yygh/blog/1822406
[ssh]: https://blog.csdn.net/whitehack/article/details/51705889