Log on to a cluster - O&M and Management Guide| Alibaba Cloud Documentation Center

This topic describes how to log on to an E-MapReduce (EMR) cluster by using an SSH key pair or password. You can log on to an EMR cluster from a computer that runs a Linux or Windows operating system.

Prerequisites

An EMR cluster is created. For more information, see Create a cluster.
Port 22 is enabled for the security group to which your cluster belongs. To enable port 22, you can turn on Remote Logon during cluster creation or manually add security group rules after the cluster is created. For more information, see Add security group rules.

Note When you add inbound security group rules, you must set Authorization Type to IPv4 CIDR Block and Port Range to 22/22.
Your computer is connected to the master node of the cluster. You can turn on Assign Public IP Address during cluster creation to associate an elastic IP address (EIP) with your cluster. Alternatively, you can assign a fixed public IP address or an EIP address to the master node of your cluster in the ECS console after the cluster is created. For more information, see Bind an ENI.

Background information

After your computer is connected to the master node of your cluster in SSH mode, you can run Linux commands to monitor the cluster and interact with the cluster. You can also create an SSH tunnel to view the web UIs of open source components. For more information, see Create an SSH tunnel to access web UIs of open source components.

Obtain the public IP address of the master node

Go to the Cluster Overview page of your cluster.
1. Log on to the Alibaba Cloud EMR console.
2. In the top navigation bar, select the region where your cluster resides and select a resource group based on your business requirements.
3. Click the Cluster Management tab.
4. On the Cluster Management page, find your cluster and click Details in the Actions column.
In the Instance Info section of the Cluster Overview page, view the public IP address of the master node.

Log on to the cluster by using an SSH key pair

Note For information about how to obtain the public IP address of the master node, see Obtain the public IP address of the master node.

Use one of the following methods to log on to the cluster:

Log on from a computer that runs a Linux operating system
The private key file ecs.pem is used in this example.
1. Run the following command to modify the attribute of the private key file:
```
chmod 400 ~/.ssh/ecs.pem
```
  ~/.ssh/ecs.pem is the path where the ecs.pem file is stored on your computer.
2. Run the following command to connect to the master node:
```
ssh -i ~/.ssh/ecs.pem root@<Public IP address of the master node>
```
Use PuTTY to log on from a computer that runs a Windows operating system
Perform the following steps to log on to the cluster:
1. Download PuTTY and PuTTYgen.
2. Convert the format of the private key file from .pem to .ppk.
  1. Run PuTTYgen. In this example, PuTTYgen 0.73 is used.
  2. In the Actions section, click Load to import the private key file that is saved when you create a cluster.
    Make sure that the format of the file to be imported is All files (*.*).
  3. Select the specific .pem file and click Open.
  4. Click Save private key.
  5. In the dialog box that appears, click Yes. Specify a name for the .ppk file and click Save.
    Save the .ppk file such as kp-123.ppk in this example to your computer.
3. Run PuTTY.
4. Choose Connection > SSH > Auth in the left-side navigation pane. Click Browse below Private key file for authentication to select the .ppk file.
5. Click Session. Enter the logon account and the public IP address of the master node in the Host Name (or IP address) field.
  The format is root@[Public IP address of the master node], such as root@10.10.xx.xx.
6. Click Open.
  If the following information appears, the logon is successful.
Use Command Prompt to log on from a computer that runs a Windows operating system
Open Command Prompt and run the following command to log on to the cluster:
```
ssh -i <Storage path of the .pem file on your computer> root@<Public IP address of the master node>
```

Log on to the cluster by using an SSH password

Note The username and password used in the following operations are the root user and the password you specified when you created a cluster. For information about how to obtain the public IP address of the master node, see Obtain the public IP address of the master node.

Procedure:

Log on from a computer that runs a Linux operating system
Run the following command in the command-line interface (CLI) of your computer to connect to the master node:
```
ssh root@[Public IP address of the master node]
```
Log on from a computer that runs a Windows operating system
1. Download and install PuTTY.
  Download link: PuTTY.
2. Start PuTTY.
3. Configure the parameters required to connect to a Linux instance.
  - Host Name (or IP address): Specify the fixed public IP address of the instance or the EIP address associated with the instance.
  - Port: Enter port number 22.
  - Connection type: Select SSH.
  - Saved Sessions: optional. Enter an informative name that is easy to identify and click Save to save the session. This way, you do not need to enter session information such as the public IP address when you connect to the instance again.
4. Click Open.
5. Specify the username (root by default) and press Enter.
  The characters of the password are hidden when you enter the password. After you enter the password, press Enter.

FAQ

Q: How do I log on to a cluster from my computer in password-free mode?
A: Perform the following steps:
1. Open Command Prompt and run the following command to generate a public key:
```
ssh-keygen
```
  A public key file is generated on your computer.
2. Add the generated public key to the master node of the cluster to which you want to log on.
  1. Go to the /.ssh directory of the cluster.
```
cd ~/.ssh
```
  2. Edit the key information of the master node of the cluster.
```
vim authorized_keys
```
  3. Add the content of the generated public key file id_rsa to the authorized_keys file.
3. Add the IP address of your computer to the security group to which the cluster belongs.
  1. Obtain the public IP address of your computer.
    For security purposes, we recommend that you allow only access from the current public IP address when you configure a security group rule. You can visit http://myip.ipip.net/ to view your public IP address.
  2. Add a security group rule with port 22 enabled.
    For more information about how to add a security group rule, see Add a security group rule.
4. Run the following command in Command Prompt to log on to the cluster in password-free mode:
```
ssh root@<Public IP address of the master node>
```
Q: How do I log on to a core node?
A: Perform the following steps:
1. On the master node, run the following command to switch to the hadoop user:
```
su hadoop
```
2. Log on to the core node in password-free mode.
```
ssh emr-worker-1
```
3. Run the following sudo command to obtain the root permissions:
```
sudo su - root
```