SSH connections to Gcore Virtual Machines use key-based authentication by default. Most failures trace back to a misconfigured key, the wrong default username, a missing floating IP, or a blocked firewall port.
Recommended SSH connection method
SSH key authentication provides better security than password-based access and is the recommended way to connect to Virtual Machines.
To set up SSH key authentication:
- Generate SSH keys or use existing ones.
- Upload the public key to the SSH Keys section.
- Select the key when creating a VM.
The private key cannot be downloaded again after creation. Save it in a secure location immediately after generating it.
Add multiple SSH keys
To allow multiple users or devices to access the same VM, add several keys through the Gcore Customer Portal when creating a VM. In the SSH key section, select multiple keys from the saved keys list. Upload additional keys from the SSH Keys section.
Cannot log in as root. Permission denied error
Gcore images have root SSH login disabled by default for security reasons.
The default username depends on the operating system. When creating a VM, the portal displays the correct username in the format ssh [username]@ipaddress.
| Operating system | Default username |
|---|
| Ubuntu | ubuntu |
| Debian | debian |
| Fedora | fedora |
| CentOS | cloud-user |
| Rocky Linux | rocky |
| SUSE | sles |
| Fedora-CoreOS | core |
| Windows | Admin (RDP only) |
[login]@[ip-of-the-VM].
After connecting with the default user, switch to root with:
Custom images may have different default usernames or allow root login. Check with the image provider for the specific access credentials.
No password received via email
Gcore does not send VM credentials via email. By default, Virtual Machines only accept SSH key authentication.
For password access to the VNC console, configure a password during VM creation.
VNC console passwords are for emergency access only. SSH key authentication is the recommended method for connecting to Virtual Machines.
Lost SSH key and cannot connect
If the private key is lost:
-
If a password was configured during VM creation: access the VM via the VNC console and add a new public key to
~/.ssh/authorized_keys.
-
If no password was configured: create a replacement VM. Save the SSH private key immediately after generation.
To prevent losing access, add multiple keys to the VM during creation or use the User Data field to configure a VNC console password as a backup access method.
Connection timed out
This error is caused by incorrect security group configuration.
Allow ICMP for connectivity testing:
| Protocol | Type | Code | Source |
|---|
| ICMP | Any | Any | 0.0.0.0/0 |
| Protocol | Port | Source |
|---|
| TCP | 22 | 0.0.0.0/0 |
Permission denied (publickey) error
PuTTY and OpenSSH use different public key formats. If the public key starts with BEGIN SSH2 PUBLIC KEY, it will not work with Gcore Virtual Machines. The key must start with ssh-rsa AAAA... (OpenSSH format).
When generating a key with PuTTYgen, copy the key from the Public key for pasting into OpenSSH authorized_keys file field at the top of the PuTTYgen window — do not use the text from Save public key.
No floating (public) IP address. Connection refused error
When creating a VM with a pre-existing subnet, it is possible to create a server without a floating (public) IP.
Without a floating IP, SSH connections from external networks are not possible because the internal IP address is not reachable from the Internet. Add a floating IP to the VM to enable external SSH access.
Cannot connect to a VM with Windows OS
SSH is not supported for Windows-based VMs, so use RDP (Remote Desktop Protocol) instead. On Windows PCs, the Remote Desktop client is installed by default.
Network appliance images (FortiGate, MikroTik)
Network appliance images use their own authentication methods, not standard SSH key authentication.
| Appliance | Default username | Default password |
|---|
| FortiGate | admin | empty (new password required on first login) |
| MikroTik CHR | admin | empty |
- VNC console in the Customer Portal
- Web interface (FortiGate:
https://[VM-IP], MikroTik: http://[VM-IP])
- SSH (after initial configuration via console)
- WinBox (MikroTik only)
