如何使 SSH 会话保持活动状态

为什么 SSH 会关闭连接？

The short answer is that it all comes down to TCP timeouts. TCP timeout refers to the duration that a TCP connection or a network operation waits for a response before considering the process failed.
简短的回答是，这一切都归结为TCP超时。TCP 超时是指 TCP 连接或网络操作在认为进程失败之前等待响应的持续时间。

In Linux, TCP timeout settings determine how long a TCP connection or operation should wait before assuming that a packet has been lost or a connection has become unresponsive.
在 Linux 中，TCP 超时设置确定 TCP 连接或操作在假定数据包已丢失或连接无响应之前应等待多长时间。

In the case of keeping the SSH connection alive, there are three key system parameters that we will briefly discuss below.
在保持 SSH 连接处于活动状态的情况下，我们将在下面简要讨论三个关键系统参数。

tcp_keepalive_time: determines the interval between sending out TCP keepalive probes on an idle TCP connection. Keepalive probes check whether a remote peer is still alive and responsive, even when no data is being transferred.
tcp_keepalive_time：确定在空闲的 TCP 连接上发送 TCP keepalive 探测之间的间隔。Keepalive 探测器检查远程对等体是否仍处于活动状态且响应迅速，即使没有传输任何数据也是如此。
**tcp_keepalive_probes**: a small packet sent by a TCP endpoint to check the health and responsiveness of the remote endpoint in an idle connection. It detects if the remote endpoint has become unreachable or the connection has been lost due to network issues.
tcp_keepalive_probes：TCP端点发送的小数据包，用于检查空闲连接中远程端点的运行状况和响应能力。它检测远程终结点是否变得无法访问或连接是否由于网络问题而丢失。
tcp_keepalive_intvl: controls the interval between sending keepalive probes on an idle TCP connection.
tcp_keepalive_intvl：控制在空闲的 TCP 连接上发送 keepalive 探测之间的间隔。

如何使 SSH 会话保持活动状态

客户端配置 （Linux）Client-Side Configuration (Linux)

在客户端，即您的 Linux 桌面系统，在您的主目录（如果尚不存在）“~/.ssh/config”中创建一个文件。

touch ~/.ssh/config

但是，如果“~/.ssh”目录不存在，则必须创建它，然后设置适当的权限。

mkdir ~/.ssh 
chmod 700 ~/.ssh

添加一下配置：

Host *
ServerAliveInterval 120
ServerAliveCountMax 30

Here’s what each option means:
以下是每个选项的含义：

In other words, the client will send a keepalive message to the server every 120 seconds (2 minutes), 30 times. 120 * 30 = 3600 seconds, or one hour. This is the total amount of time for which, even without activity, our SSH session will be kept alive.
换句话说，客户端将每 120 秒（2 分钟）向服务器发送一条 keepalive 消息，共 30 次。120 * 30 = 3600 秒，即 1 小时。这是即使没有活动，我们的 SSH 会话也将保持活动状态的总时间。

服务器端配置

更改服务器的超时选项会影响连接到服务器的所有客户端。您需要编辑“/etc/ssh/sshd_config”文件才能执行此操作。

sudo vi /etc/ssh/sshd_config

然后设置以下三个选项：

TCPKeepAlive yes
ClientAliveInterval 120 
ClientAliveCountMax 30

Here’s what each of these three options means:
以下是这三个选项中每个选项的含义：