How do I connect to a Redis server using the redis-cli command-line interface?

This article explains connecting to a Redis server using redis-cli, detailing connection parameters (host, port, password, socket, cluster mode, database selection) and troubleshooting steps (server status, firewall, network, password, socket, cluste

Connecting to a Redis Server using redis-cli

Connecting to a Redis server using the redis-cli command-line interface is straightforward. The simplest way is to just type redis-cli in your terminal. This will attempt to connect to a Redis server running on the localhost (127.0.0.1) on the default port 6379. If your Redis server is running on a different machine or port, you'll need to specify the host and port using the -h (or --host) and -p (or --port) options respectively.

For example, to connect to a server running on 192.168.1.100 on port 6380, you would use:

redis-cli -h 192.168.1.100 -p 6380

If you are using a password to protect your Redis instance, you'll need to use the -a (or --password) option followed by your password:

redis-cli -h 192.168.1.100 -p 6380 -a mysecretpassword

Upon successful connection, you'll be presented with the Redis command prompt, typically indicated by a blank line or a prompt like 127.0.0.1:6379>.

Common Connection Parameters for redis-cli

Beyond the host, port, and password, redis-cli offers several other useful connection parameters:

• -h <host></host> or --host <host></host>: Specifies the hostname or IP address of the Redis server. Defaults to 127.0.0.1.
• -p <port></port> or --port <port></port>: Specifies the port number the Redis server is listening on. Defaults to 6379.
• -a <password></password> or --password <password></password>: Specifies the password for authentication. Required if your Redis server is password-protected.
• -s or --socket <socket></socket>: Specifies the path to a Unix domain socket. This is an alternative to connecting via TCP/IP.
• -c or --cluster: Indicates that you're connecting to a Redis Cluster. redis-cli will then automatically handle the cluster topology.
• -n <db></db> or --db <db></db>: Specifies the database to select after connecting. Redis databases are numbered starting from 0.

Using these parameters allows for flexible connection to various Redis server configurations.

Troubleshooting Connection Issues with redis-cli

Troubleshooting connection issues involves systematically checking several aspects:

1. Verify Redis Server Status: Ensure your Redis server is running and listening on the specified host and port. Check the Redis server logs for any errors. Use systemctl status redis-server (or the equivalent for your system) to check its status.
2. Firewall Rules: Make sure your firewall allows connections to the specified port. If connecting from a remote machine, ensure the firewall on both the client and server machines permits the connection.
3. Network Connectivity: Confirm network connectivity between the client machine and the Redis server. Try pinging the server's IP address.
4. Correct Host and Port: Double-check that you've entered the correct hostname, IP address, and port number in your redis-cli command. Typos are a common cause of connection failures.
5. Password Authentication: If your Redis server requires a password, ensure you've provided the correct password using the -a option. Incorrect passwords will result in connection refusal.
6. Unix Socket: If using a Unix socket, verify the socket file exists and has the correct permissions.
7. Redis Cluster: If connecting to a Redis Cluster, make sure the cluster is properly configured and running. Use the CLUSTER NODES command within redis-cli to inspect the cluster state.

By systematically checking these points, you should be able to pinpoint the cause of the connection problem.

Performing Basic Redis Commands with redis-cli

Yes, once connected to a Redis server using redis-cli, you can execute all the standard Redis commands. These commands are used to interact with the data stored in the Redis database. Some examples include:

• SET key value: Sets the value associated with a key.
• GET key: Retrieves the value associated with a key.
• DEL key: Deletes a key.
• KEYS *: Lists all keys in the current database.
• FLUSHALL: Clears all data from all databases. Use with caution!
• FLUSHDB: Clears all data from the current database. Use with caution!
• INCR key: Increments the integer value associated with a key.
• LPUSH list value: Adds a value to the left of a list.

After connecting, simply type the commands at the prompt and press Enter. redis-cli will execute the command and display the result. Refer to the official Redis documentation for a comprehensive list of available commands and their usage. Remember to consult the Redis documentation for the correct syntax and usage of each command.

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