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Sharing and Collaboration

The gns3util share command group packages configuration artifacts so that administrators on the same network can exchange ready-to-use lab environments. Transfers rely on a secure QUIC tunnel with short-authentication-string (SAS) verification to prevent tampering by students.

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When to Use Sharing

  • Hand off a fully provisioned cluster configuration to another instructor
  • Sync updates to the GNS3 database (clusterData.db) across lab administrators

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Sending Artifacts

Run share send from the machine that already has the desired artifacts. 
# Launch share send and choose artifacts/receiver interactively
gns3util share send

# Send cluster config, database, and key file to a discovered receiver
gns3util share send --all

# Send only the cluster config to another device discovered via mDNS
gns3util share send \
  --send-config \
  --src-dir ~/.gns3 \
  --discover-timeout 10

# Discover nearby receivers, fuzzy-pick, and send only the key file
gns3util share send \
  --send-key \
  --discover-timeout 5

# Share only the database file during a fuzzy picker window
gns3util share send \
  --send-db \
  --src-dir ~/.gns3

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Flags

  • --all: Include cluster_config.toml, clusterData.db, and gns3key
  • --send-config: Only send the config file
  • --send-db: Only send the database file
  • --send-key: Only send the key file
  • --discover-timeout <duration>: Adjust the mDNS discovery window (default 3s)
  • --src-dir <path>: Choose a different artifact directory (default ~/.gns3)
  • --to <label|host:port>: Skip interactive selection and dial a specific receiver
  • --yes: Accept prompts automatically (useful for automation)
If you omit --to, the command discovers nearby receivers via mDNS and lets you pick one interactively.

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Receiving Artifacts

Run share receive on the target machine and leave the terminal open while waiting for a sender. 
# Host a receiver and wait for transfers
gns3util share receive
The command announces itself over mDNS, displays the SAS when a sender connects, and waits for you to confirm the transfer. Files are placed in your ~/.gns3 directory by default.

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Secure Workflow

  1. Receiver prepares: Run gns3util share receive on the destination host.
  2. Sender selects artifacts: Choose --all or the individual --send-* flags.
  3. Verify SAS: Both sides compare the SAS displayed in their terminals.
  4. Complete transfer: Approve on both ends; artifacts are copied over QUIC.
  5. Apply artifacts: On the receiver, use gns3util cluster config apply or other commands to load the new data.

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Tips

  • Use --discover-timeout 0 to disable discovery if you must specify --to manually.
  • Combine --yes with cron jobs or systemd timers for unattended nightly transfers.
  • Combine sharing with version-controlled config files to keep lab environments reproducible.
  • Run gns3util share send --help and gns3util share receive --help to view the full flag set and defaults before scripting automation.
  • The receiver binds to a random UDP port and advertises it via mDNS; expect port numbers to change on each run. If you see a buffer warning from QUIC (similar to failed to sufficiently increase receive buffer size), follow the guidance at https://github.com/quic-go/quic-go/wiki/UDP-Buffer-Sizes to tune your OS settings.