Mismatched SSH protocol versions

Oct 13, 2025 by wbrum.org 34 views

Introduction

Connecting to a Synology NAS using PuTTY terminal can be a convenient way to manage and configure your device remotely. However, some users have reported encountering a spurious message "Display all possibilities? (y or n)" in the PuTTY terminal. This issue can be frustrating, especially when trying to troubleshoot or perform administrative tasks on the NAS. In this article, we will explore the possible causes of this issue and provide step-by-step solutions to resolve it.

Understanding the Issue

The "Display all possibilities? (y or n)" message is typically associated with the SSH protocol, which is used by PuTTY to establish a secure connection to the Synology NAS. This message is usually displayed when the SSH client (PuTTY) is unable to determine the correct terminal type or when there is a mismatch between the client and server settings.

Possible Causes

There are several possible causes for this issue, including:

Incorrect terminal type: The terminal type set in PuTTY may not match the actual terminal type used by the Synology NAS.
Mismatched SSH protocol versions: The SSH protocol version used by PuTTY may not be compatible with the version used by the Synology NAS.
Incorrect SSH key settings: The SSH key settings in PuTTY may not be correctly configured, leading to authentication issues.
Synology NAS firmware issues: In some cases, the issue may be related to a firmware bug or incompatibility in the Synology NAS.

Troubleshooting Steps

To resolve the "Display all possibilities? (y or n)" issue, follow these troubleshooting steps:

Step 1: Check the Terminal Type

Open PuTTY and navigate to Connection > SSH > Terminal type.
Ensure that the terminal type is set to xterm or vt100. These are the most common terminal types used by Synology NAS devices.
If you are unsure about the terminal type, try setting it to xterm and see if the issue resolves.

Step 2: Verify SSH Protocol Versions

Open PuTTY and navigate to Connection > SSH > Protocol version.
Ensure that the SSH protocol version is set to 2.0 or 2.1. These are the most commonly used SSH protocol versions.
If you are unsure about the SSH protocol version, try setting it to 2.0 and see if the issue resolves.

Step 3: Check SSH Key Settings

Open PuTTY and navigate to Connection > SSH > Auth.
Ensure that the Private key file for authentication is set to the correct location and file name.
If you are using a public key for authentication, ensure that the Public key file for authentication is set to the correct location and file name.

Step 4: Update Synology NAS Firmware

If you are using an older version of the Synology NAS firmware, try updating to the latest version.
Ensure that the firmware update is compatible with your device model.

Step 5: Reset PuTTY Settings

If none of the above steps resolve the issue, try resetting PuTTY settings to their default values.
Open PuTTY and navigate to File > Default Settings.
Click Save to save the default settings.

Conclusion

The "Display all possibilities? (y or n)" issue in PuTTY terminal connected to a Synology NAS can be frustrating, but it is often resolvable by following the troubleshooting steps outlined above. By checking the terminal type, verifying SSH protocol versions, checking SSH key settings, updating Synology NAS firmware, and resetting PuTTY settings, you should be able to resolve the issue and establish a secure connection to your Synology NAS device.

Additional Tips

Ensure that you are using the latest version of PuTTY and Synology NAS firmware.
If you are still experiencing issues, try contacting Synology support for further assistance.
Consider using an alternative SSH client, such as OpenSSH, to rule out any client-side issues.

Frequently Asked Questions

Q: What is the "Display all possibilities? (y or n)" message?

A: The "Display all possibilities? (y or n)" message is a spurious message displayed in the PuTTY terminal when the SSH client is unable to determine the correct terminal type or when there is a mismatch between the client and server settings.

Q: How do I resolve the "Display all possibilities? (y or n)" issue?

A: To resolve the issue, follow the troubleshooting steps outlined above, including checking the terminal type, verifying SSH protocol versions, checking SSH key settings, updating Synology NAS firmware, and resetting PuTTY settings.

Q: Can I use an alternative SSH client to resolve the issue?

Q: What is the "Display all possibilities? (y or n)" message?

Q: How do I resolve the "Display all possibilities? (y or n)" issue?

Q: What are the possible causes of the "Display all possibilities? (y or n)" issue?

A: The possible causes of the "Display all possibilities? (y or n)" issue include:

Incorrect terminal type
Mismatched SSH protocol versions
Incorrect SSH key settings
Synology NAS firmware issues

Q: How do I check the terminal type in PuTTY?

A: To check the terminal type in PuTTY, follow these steps:

Open PuTTY and navigate to Connection > SSH > Terminal type.
Ensure that the terminal type is set to xterm or vt100. These are the most common terminal types used by Synology NAS devices.
If you are unsure about the terminal type, try setting it to xterm and see if the issue resolves.

Q: How do I verify SSH protocol versions in PuTTY?

A: To verify SSH protocol versions in PuTTY, follow these steps:

Open PuTTY and navigate to Connection > SSH > Protocol version.
Ensure that the SSH protocol version is set to 2.0 or 2.1. These are the most commonly used SSH protocol versions.
If you are unsure about the SSH protocol version, try setting it to 2.0 and see if the issue resolves.

Q: How do I check SSH key settings in PuTTY?

A: To check SSH key settings in PuTTY, follow these steps:

Open PuTTY and navigate to Connection > SSH > Auth.
Ensure that the Private key file for authentication is set to the correct location and file name.
If you are using a public key for authentication, ensure that the Public key file for authentication is set to the correct location and file name.

Q: Can I use an alternative SSH client to resolve the issue?

A: Yes, you can try using an alternative SSH client, such as OpenSSH, to rule out any client-side issues.

Q: How do I update Synology NAS firmware?

A: To update Synology NAS firmware, follow these steps:

Log in to your Synology NAS device using the web interface.
Navigate to Control Panel > Firmware Update.
Click Update Now to download and install the latest firmware.

Q: Can I reset PuTTY settings to their default values?

A: Yes, you can reset PuTTY settings to their default values by following these steps:

Open PuTTY and navigate to File > Default Settings.
Click Save to save the default settings.

Q: What if I am still experiencing issues after trying the troubleshooting steps?

A: If you are still experiencing issues after trying the troubleshooting steps, try contacting Synology support for further assistance. They may be able to provide additional guidance or troubleshooting steps specific to your device.

Q: Can I use a different SSH client to connect to my Synology NAS device?

A: Yes, you can try using a different SSH client, such as OpenSSH, to connect to your Synology NAS device. This may help you determine if the issue is specific to PuTTY or if it is a problem with your device or network configuration.