SSH Troubleshooting Information

This guide explains how to troubleshoot common SSH connection and performance problems on your Ultra service, including authentication failures, temporary IP blocks, host-key warnings, high disk I/O, and process-limit errors.

For initial connection instructions, see Connect to your Ultra slot via SSH.

Check Your Connection Details

Your SSH connection details are available in the Connect tab of the User Control Panel.

Confirm that you are using:

Hostname: <servername>.usbx.me or <service-IP-address>
Username: <your-Ultra-service-username>
Password: <your-SSH/FTP-password>
Port: 22

• Use your Ultra service username, not your Client Area email address.
• Use the hostname or IP address currently displayed in the User Control Panel.
• Use port 22.
• Use your current SSH/FTP password.
• Update any saved password in your SSH or SFTP client after changing it in the User Control Panel.
• You can connect with OpenSSH using one of these formats:

ssh <username>@<service-IP-address>
ssh <username>@<servername>.usbx.me
ssh <username>@<username>.<servername>.usbx.me

• Replace the placeholders with the details displayed in the Connect tab.

Troubleshoot a Timed-Out Connection

Several failed login attempts may temporarily block your public IP address.

• Stop attempting to connect.
• Confirm that your username, hostname, and port are correct.
• Reset your SSH/FTP password if you are unsure of it.
• Wait at least 10 minutes.
• Try connecting again with the correct details.

• If possible, test the connection from another network, such as a mobile hotspot. A successful connection from another network indicates that your original public IP address may still be temporarily blocked.
• If the connection continues to time out after the waiting period, open a support ticket.

Troubleshoot Permission Denied

If SSH displays Permission denied, check the following:

• Confirm that you are using your Ultra service username, not your Client Area email address.
• Confirm that the hostname or IP address matches the Connect tab.
• Confirm that the port is 22.
• Confirm that you are using your current SSH/FTP password.
• Update any saved password in your SSH or SFTP client.
• Check whether your SSH client is attempting to use an incorrect saved key or identity.
• Wait a few minutes after changing your password before trying again.

If authentication still fails:

• Open the User Control Panel.
• Select Connect for your service.
• Open the Connect tab.
• Click Change password beside SSH access.
• Set a new SSH/FTP password.
• Update the saved password in your SSH or SFTP client.
• Try connecting again.
• SSH and SFTP use the same SSH/FTP password.

Troubleshoot Connection Refused

If SSH displays Connection refused:

• Confirm that the port is 22.
• Confirm that you are using the current hostname or IP address from the User Control Panel.
• Try connecting with the service hostname.
• Try connecting with the service IP address.
• If the hostname fails but the IP address works, the issue may be related to DNS resolution on your device or network.
• If both connection methods fail, open a support ticket.

Resolve a Changed Host Key

• SSH may display a warning such as:

REMOTE HOST IDENTIFICATION HAS CHANGED

This warning means that the host key presented by the server differs from the key saved on your device.

• Do not bypass the warning without confirming why the host key changed.
• Check whether your service was recently migrated or moved to another server.
• Confirm that you are using the current hostname or IP address from the User Control Panel.
• Contact Ultra support if the change is unexpected.

• After confirming that the change is legitimate, remove the outdated key:

ssh-keygen -R <hostname>

• If you connect by IP address, also remove the saved entry for that address:

ssh-keygen -R <service-IP-address>

• Reconnect and review the new host-key prompt before accepting it.

Check Disk I/O

High disk I/O can make applications, file transfers, WebUIs, and SSH sessions respond slowly.

Common causes include:

• Torrent clients checking torrents
• Large numbers of active torrents
• Usenet downloading, repairing, or unpacking
• Unpacking large archives
• Media-library scans
• Continuous Rclone operations
• Multiple simultaneous FTPS or SFTP transfers
• Moving or deleting large directories
• Several applications performing disk-intensive work simultaneously
• HDD-based services can also be affected by other users sharing the same disk. NVMe services are less susceptible because they provide substantially higher I/O throughput.
• Connect through SSH and run:

iostat -xk 2 "$(findmnt -T "$HOME" | awk 'END {print $2}')"

Watch the %util column.

• Short spikes are normal.
• If %util remains close to 100% for an extended period, the disk is saturated.
• Sustained saturation can affect applications, file transfers, SSH responsiveness, and WebUI loading.
• Press Ctrl+C to stop the command.

Reduce Disk I/O

If disk I/O is high:

• Limit active torrent downloads.
• Pause or reduce torrent checking.
• Avoid unpacking while downloads are active.
• Reduce Usenet download, repair, and unpack concurrency.
• Pause large FTPS or SFTP transfers.
• Reduce the number of parallel transfer streams.
• Pause media-library scans.
• Avoid heavy Rclone operations while other disk-intensive tasks are running.
• Use application queueing features where available.
• Run the disk-I/O check again after reducing activity.
• If utilization remains high and your processes do not appear responsible, open a support ticket so the Ultra.cc team can investigate the shared disk.

Identify Disk-Intensive Processes

Use htop

Run:

htop

Look for the DISK R/W column, which displays each process’s disk read-and-write rate.

The displayed units may include:

• B/s — bytes per second
• K/s — kilobytes per second
• M/s — megabytes per second

If the column is not visible:

• Press F2 to open Setup.
• Select Columns.
• Open Available Columns.
• Find IO_RATE.
• Press Enter to add it to Active Columns.
• Use F7 and F8 to reposition the column if necessary.
• Press F10 to exit setup.

Use pidstat

Run:

pidstat -dl 2

• This command reports per-process disk activity at regular intervals.
• If a specific application or command is producing heavy activity, reduce its concurrency, pause it, or stop it temporarily.

Resolve Process-Limit Errors

• A process or thread limit may have been reached if SSH displays an error such as:

Resource temporarily unavailable

su: failed to execute /bin/bash: Resource temporarily unavailable

shell request failed

• Ultra services use process and thread limits to maintain fair usage on shared servers. New shells and application processes may fail to start when an application or script creates too many processes or threads.

Common causes include:

• Rclone or Syncthing using excessive concurrency
• Cloud-sync tools or tunnel services
• Custom scripts spawning many workers
• Python, Java, or Node applications using too many threads
• Misconfigured plugins or background services
• Applications stuck in a crash loop

If the User Control Panel remains accessible:

• Stop recently installed or resource-intensive applications.
• Wait briefly.
• Try opening a new SSH connection.
• Reduce the offending application’s worker, thread, or concurrency settings before restarting it.

If you cannot access SSH or stopping applications does not restore access, open a support ticket. Support can identify the offending process and reset the account state if necessary.

Manage Files and Free Space

Use an FTPS or SFTP client when you need a graphical file-management interface.

SFTP is recommended when you need:

• Access to files throughout your home directory
• SSH-key authentication
• Secure transfers over port 22

For connection instructions, see Connect to your Ultra slot with FTP.

• For terminal-based file management, run Midnight Commander:

mc

• Midnight Commander provides a two-panel, terminal-based file manager.
• To identify directories consuming storage, run:

ncdu -x "$HOME"

Check Whether Files Are Hardlinked

Radarr, Sonarr, and similar applications can create hardlinks instead of separate copies when:

• Hardlinking is enabled in the application.
• The source and destination are on the same filesystem.
• The paths and permissions allow hardlink creation.
• A hardlink gives the same file data more than one path. It does not store a second copy of the file’s contents. Storage is released only after the final hardlink to the data is removed.
• Compare the inode numbers of the suspected files:

ls -li "/path/to/first-file" "/path/to/second-file"

• If both files have the same inode number, they are hardlinks to the same data.
• You can also run:

stat -c '%i %n' "/path/to/first-file" "/path/to/second-file"

• Matching inode numbers confirm that the paths refer to the same file data.
• For an interactive storage overview, run:

ncdu -x "$HOME"

• In ncdu, files marked with an uppercase H are hardlinks.
• For more information, see the Hard link article.

If you require further assistance, you can open a support ticket here.

• SSH Troubleshooting Information
• Check Your Connection Details
• Troubleshoot a Timed-Out Connection
• Troubleshoot Permission Denied
• Troubleshoot Connection Refused
• Resolve a Changed Host Key
• Check Disk I/O
• Reduce Disk I/O
• Identify Disk-Intensive Processes
• Use htop
• Use pidstat
• Resolve Process-Limit Errors
• Manage Files and Free Space
• Check Whether Files Are Hardlinked