How to configure Docker template preferences
Docker is a node type in GNS3 based on container technology. Unlike QEMU/Dynamips virtual machines, Docker shares the host machine kernel. It starts very fast.
Create a Template
This example uses an Ubuntu container to show how to create a Docker template.
Click the "Docker" option to enter.
Click the + button at the top right to add a new template.
Follow the wizard steps. Click "Docker Virtual Machine".
If the image already exists, choose "Existing image" and select it from the list. Then click "Container name".
If the image does not exist, choose "New image". Enter the image name in "Image name" (e.g.
ubuntu:latest). Then click "Container name".
In "Container name", enter the container template name. Then click "Network adapters".
In "Network adapters", set the number of interfaces. Then click "Start command".
In "Start command", enter the startup parameters. Then click "Console type".
Choose the console type based on the container type (telnet/vnc, etc.). Then click "Auxiliary console type".
Set "Auxiliary console type" to "None". Then click "Environment".
In "Environment", set the container environment variables. Then click "Add Template" to finish.
After creation, you can see the new template in the list.
Click the three-dot button on the right to choose Delete, Copy, or Edit.
Differences from Other Node Types
| Feature | Docker | QEMU | Dynamips | VPCS |
|---|---|---|---|---|
| Technology type | Container (shared kernel) | Full virtualization | Hardware simulation | Simulated PC |
| Startup speed | Very fast (seconds) | Slow (minutes) | Slow | Fast |
| Image size | Small (layered storage) | Large (several GB) | Medium | Very small |
| Number of NICs | 0-100 | 0-275 | Depends on platform | 1 |
| Console types | 8 types | 7 types | telnet/ssh | telnet |
| Memory limit | Optional (0 = no limit) | Required | Required | None |
| CPU limit | Optional (supports decimals) | Required | Required | None |
Docker Template Configuration Details
General Settings
| Field | Type | Unit | Use |
|---|---|---|---|
| Template name | Text | -- | Name of the template, shown in the list |
| Default name format | Text | -- | Auto-naming format for instances, e.g. {name}-{0} |
| Image | Text | -- | Docker image name (e.g. ubuntu:latest) |
| Category | Dropdown | -- | Device category |
| Symbol | Text + button | -- | Topology icon |
| Tags | Chip input | -- | Tags for sorting/filtering |
| Adapters | Number | count | Number of network adapters, default is 0 |
| Base MAC | Text | -- | Base MAC address, leave empty for auto-generation |
| Maximum memory | Number | MB | Memory limit, 0 = no limit |
| Maximum CPUs | Number | count | CPU core limit, 0 = no limit |
| Console type | Dropdown | -- | telnet / ssh / vnc / http / https / none |
| Auxiliary console type | Dropdown | -- | Auxiliary console type |
| VNC console resolution | Dropdown | -- | VNC resolution, only works when console_type is vnc |
| HTTP port in the container | Number | -- | HTTP port number inside the container |
| HTTP path | Text | -- | HTTP path, e.g. /, /gui |
| Auto start console | Checkbox | -- | Automatically opens the console when enabled |
| Edit network configuration | Button | -- | Customize NIC MAC addresses |
Custom Network Configuration
Click "Edit network configuration" to open the dialog. One NIC per row:
| Column | Field type | Use |
|---|---|---|
| Adapter | Read-only label | NIC number, auto-increment |
| Port name | Read-only text | Port name, fixed as eth0, eth1... (Docker convention) |
| MAC address | Text input | MAC address, can be customized. Leave empty for auto-generation |
| Action | Delete button | Delete this NIC |
Advanced Settings
Start Command
| Field | Type | Use |
|---|---|---|
| Start command | Text area | Container startup command. Overrides the Docker image default CMD |
Environment
| Field | Type | Use |
|---|---|---|
| Environment | Text area | Environment variables, one per line, format KEY=VALUE. Supports template variables: %vm-name%, %vm-id%, %project-id%, %project-path% |
Example:
DB_HOST=192.168.1.10
DB_PORT=5432
API_KEY=%vm-id%
PROJECT=%project-id%
Extra Volumes
| Field | Type | Use |
|---|---|---|
| Extra volumes | Text area | Extra mounted volumes. One container directory path per line. Data is not lost when the container is deleted |
Example:
/data
/config
/var/log/app
Extra Hosts
| Field | Type | Use |
|---|---|---|
| Extra hosts | Text area | Extra hostname mappings. One per line, format hostname:IP |
Example:
gns3.local:192.168.100.10
database.internal:10.0.0.5
api.example.com:172.16.0.100
