SSH命令执行挂起，尽管交互式shell功能很好 [英] SSH Command Execution Hangs, although interactive shell functions fine

问题描述

当我尝试使用ssh在远程服务器上执行命令时，ssh命令在exec request accepted调试消息后挂起，并最终超时.

When I attempt to execute a command on a remote server with ssh, the ssh command hangs after the exec request accepted debug message, and eventually times out.

失败的命令:ssh -v -v <username>@<server> uptime(也尝试过echo hello等)

The failing command: ssh -v -v <username>@<server> uptime (also tried echo hello etc.)

debug1: Authentication succeeded (publickey).
Authenticated to <server> (<ip>:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting [e-mail]
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: fd 4 setting TCP_NODELAY
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug1: Sending command: uptime
debug2: channel 0: request exec confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: exec request accepted on channel 0

它无限期地挂着.

但是，当我在没有命令的情况下将ssh放入远程服务器时，我得到了一个交互式shell，一切都很好.

When I ssh without a command into my remote server, however, I get an interactive shell and all is good.

成功的命令:ssh -v -v <username>@<server>

输出:

debug1: Authentication succeeded (publickey).
Authenticated to <server> (<ip>:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting [e-mail]
debug1: Entering interactive session.
debug2: callback start
debug2: client_session2_setup: id 0
debug2: fd 4 setting TCP_NODELAY
debug2: channel 0: request pty-req confirm 1
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
debug2: channel 0: request env confirm 0
debug2: channel 0: request shell confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Welcome!
<prompt>%
...

有人知道为什么交互式会话会成功但命令执行不成功吗?

Has anyone an idea why an interactive session would be successful but a command execution not?

已经困扰我几个月了，因为我再也无法使用统一来同步我的文件了(它曾经可以工作).任何帮助表示赞赏.

Has been haunting me for months now because I cannot use unison to sync my files any more (it used to work). Any help much appreciated.

推荐答案

问题确实是我的登录脚本，尽管与要求终端无关(我怀疑是这样，并用-t和-T进行了测试选项).问题是我的.bashrc正在运行exec(在本例中为zsh-因为我们的系统不允许chsh至zsh).

The problem was indeed my login script, although not to do with requiring a terminal (I'd suspected that and tested with the -t and -T options). The problem was that my .bashrc was running an exec (in this case to zsh - because our system doesn't allow chsh to zsh).

违规行:

test -f /usr/bin/zsh && exec /usr/bin/zsh

已通过首先检查交互式外壳程序并退出(如果是)来解决:

Solved by first checking for interactive shell and exiting if so:

[ -z "$PS1" ] && return
test -f /usr/bin/zsh && exec /usr/bin/zsh

因此，从本质上讲，由于shell正在执行zsh，因此ssh一直在等待此操作完成-从未发生.

So, essentially, because the shell was execing into zsh, ssh was waiting for this to finish - which never happened.

我有点困惑为什么我的.bashrc被调用-我以为这只是用于交互式shell，但是各种初始化脚本的确切目的和顺序是我永远不会想到的.学习.

I am a little confused why my .bashrc was being called at all - I thought this was only for interactive shells, but the exact purpose and order of the various init scripts is something I don't think I'll ever learn.

我希望这对其他在启动脚本中使用exec的人有用.

I hope this can be useful to others who have some kind of exec in their startup scripts.

顺便说一句-其他两个答案都在正确的轨道上，所以我完全不确定我应该回答"还是只是评论他们的答案.如果在stackoverflow上回答我自己的问题在道德上是错误的，请告诉我，我会做的.谢谢其他答复者.

BTW - the other two answers were on the right track so I was completely unsure if I should 'answer' or just comment their answers. If answering my own question is morally wrong on stackoverflow, let me know and I'll do penitence. Thank you to the other answerers.

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