断开连接并打开ssh时终端挂起

当我在gnome终端选项卡中通过Internet SSH到服务器时，如果我失去了互联网连接，则终端选项卡将挂起并且不接受任何输入。为什么挂了？

有什么方法可以激活终端选项卡，即使其继续运行本地Shell进程吗？

关闭终端标签是唯一的方法吗？

在由ClientAliveInterval和ClientAliveCountMax参数以及它们的客户端等效设置所设置的指定时间后，SSH连接会自动断开。如果这些超时时间很高，您将遇到冻结的外壳。但是，如果您使用OpenSSH它，则不必等待超时，并且可以使用转义字符强制关闭连接：

ESCAPE CHARACTERS
When a pseudo-terminal has been requested, ssh supports a number
of functions through the use of an escape character.  A single
tilde character can be sent as ~~ or by following the tilde by a
character other than those described below. The escape character
must always follow a newline to be interpreted as special. The
escape character can be changed in configuration files using the
EscapeChar configuration directive or on the command line by the
-e option.
The supported escapes (assuming the default ‘~’) are:

~.
    Disconnect.
(...)

当连接冻结时，按~（即同时按Shift+ `键），将其释放并按.。另外，如果您使用不稳定的连接，或者需要始终连接到远程服务器，则可以使用autossh自动更新丢失的连接，这非常方便。

编辑：

但是，如果将ClientAliveInterval和ServerAliveInterval都显式设置为0或未显式设置，然后根据sshd_config和ssh_config联机帮助页将它们默认设置为0，则在以下文件中设置超时设置（来自http://tldp.org/HOWTO/TCP- Keepalive-HOWTO / usingkeepalive.html）：

  # cat /proc/sys/net/ipv4/tcp_keepalive_time
  7200

  # cat /proc/sys/net/ipv4/tcp_keepalive_intvl
  75

  # cat /proc/sys/net/ipv4/tcp_keepalive_probes
  9

  The first two parameters are expressed in seconds, and the last is
  the pure number. This means that the keepalive routines wait for
  two hours (7200 secs) before sending the first keepalive probe,
  and then resend it every 75 seconds. If no ACK response is
  received for nine consecutive times, the connection is marked as
  broken.

您可以使用来修改这3个文件，echo并根据这些值查看冻结的SSH会话是否断开连接。