Add document for tiup-cluster (pingcap#3778)

* Add document for tiup-cluster

* Update tiup-cluster.md

* Update tiup/tiup-cluster.md

Co-authored-by: Ran <[email protected]>

Author: TomShawn

maintain-tidb-using-tiup.md

@@ -159,6 +159,9 @@ Flags:
       --transfer-timeout int   Timeout in seconds when transferring PD and TiKV store leaders (default 300)
 
 Global Flags:
+
+      --native-ssh        Use the system's native SSH client
+      --wait-timeout int  Timeout of waiting the operation
       --ssh-timeout int   Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
   -y, --yes               Skip all confirmations and assumes 'yes'
 ```

tiup/tiup-cluster.md

@@ -49,6 +49,8 @@ Available Commands:
 
 Flags:
   -h, --help              help for cluster
+      --native-ssh        Use the system's native SSH client
+      --wait-timeout int  Timeout of waiting the operation
       --ssh-timeout int   Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
   -y, --yes               Skip all confirmations and assumes 'yes'
 ```
@@ -351,6 +353,8 @@ Flags:
       --transfer-timeout int   Timeout in seconds when transferring PD and TiKV store leaders (default 300)
 
 Global Flags:
+      --native-ssh        Use the system's native SSH client
+      --wait-timeout int  Timeout of waiting the operation
       --ssh-timeout int   Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
   -y, --yes               Skip all confirmations and assumes 'yes'
 ```
@@ -409,6 +413,8 @@ Flags:
       --transfer-timeout int   Timeout in seconds when transferring PD and TiKV store leaders (default 300)
 
 Global Flags:
+      --native-ssh        Use the system's native SSH client
+      --wait-timeout int  Timeout of waiting the operation
       --ssh-timeout int   Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
   -y, --yes               Skip all confirmations and assumes 'yes'
 ```
@@ -459,6 +465,8 @@ Flags:
   -r, --rename NAME        Rename the imported cluster to NAME
 
 Global Flags:
+      --native-ssh        Use the system's native SSH client
+      --wait-timeout int  Timeout of waiting the operation
       --ssh-timeout int   Timeout in seconds to connect host via SSH, ignored for operations that don't need an SSH connection. (default 5)
   -y, --yes               Skip all confirmations and assumes 'yes'
 ```
@@ -613,6 +621,37 @@ When running the checks, if the `--apply` flag is specified, the program automat
 
 Environment checks are not necessary for deploying a cluster. For the production environment, it is recommended to perform environment checks and pass all check items before deployment. If not all the check items are passed, the cluster might be deployed and run normally, but the best performance might not be obtained.
 
+## Use the system's native SSH client to connect to cluster
+
+All operations above performed on the cluster machine use the SSH client embedded in TiUP to connect to the cluster and execute commands. However, in some scenarios, you might also need to use the SSH client native to the control machine system to perform such cluster operations. For example:
+
+- To use a SSH plug-in for authentication
+- To use a customized SSH client
+
+Then you can use the `--native-ssh` command-line flag to enable the system-native command-line tool:
+
+- Deploy a cluster: `tiup cluster deploy <cluster-name> <version> <topo> --native-ssh`
+- Start a cluster: `tiup cluster start <cluster-name> --native-ssh`
+- Upgrade a cluster: `tiup cluster upgrade ... --native-ssh`
+
+You can add `--native-ssh` in all cluster operation commands above to use the system's native SSH client.
+
+To avoid adding such a flag in every command, you can use the `TIUP_NATIVE_SSH` system variable to specify whether to use the local SSH client:
+
+```sh
+export TIUP_NATIVE_SSH=true
+# or
+export TIUP_NATIVE_SSH=1
+# or
+export TIUP_NATIVE_SSH=enable
+```
+
+If you specify this environment variable and `--native-ssh` at the same time, `--native-ssh` has higher priority.
+
+> **Note:**
+>
+> During the process of cluster deployment, if you need to use a password for connection (`-p`) or `passphrase` is configured in the key file, you must ensure that `sshpass` is installed on the control machine; otherwise, a timeout error is reported.
+
 ## Migrate control machine and back up TiUP data
 
 The TiUP data is stored in the `.tiup` directory in the user's home directory. To migrate the control machine, you can take the following steps to copy the `.tiup` directory to the corresponding target machine:
@@ -626,4 +665,4 @@ The TiUP data is stored in the `.tiup` directory in the user's home directory. T
 
 > **Note:**
 >
-> It is recommended that you back up the `.tiup` directory regularly to avoid the loss of TiUP data caused by abnormal conditions, such as disk damage of the control machine. 
+> It is recommended that you back up the `.tiup` directory regularly to avoid the loss of TiUP data caused by abnormal conditions, such as disk damage of the control machine.