Small and old gateways with tedge-dot-c

Many OT gateways in the field run an old distribution on a 32-bit ARM board with little storage. A binary built on a current distribution will not even start there: a native build on ubuntu-24.04 hard-requires glibc 2.39 on the target.

What you’ll build: a tedge-dot-c install on such a gateway, the default package, with the same configs, flows and cloud integration as tedge-dot-rs, and a clear picture of the few features only the Rust build has.

Not sure which package you need?

The package picker asks about your architecture, distribution and protocols, and explains its recommendation.

What the C package gives you

tedge-dot-c is a maintained peer of the Rust implementation, not a prototype. It ships from the same release, runs the same e2e, cloud and conformance suites, and is held to the same OT Connector Contract.

	tedge-dot-rs	tedge-dot-c
Architectures	amd64, arm64	amd64, arm64, armhf
Minimum glibc	not pinned	2.17 (Debian 8 / RHEL 7 era)
Binary size, all protocols	about 12 MB, static	about 457 KB (open62541 statically linked)
Protocols	Modbus, OPC UA, CAN bus, CANopen, SNMP, AVEVA PI (preview)	the same, plus PROFIBUS-DP (preview)

The glibc floor comes from the build: every architecture is cross-compiled with zig, which supplies the compiler and a libc pinned to 2.17, against Debian’s multiarch libraries. See Cross-compilation for the details.

Both packages install the same /usr/bin/tedge-dot, the same tedge-dot.service and the same /etc/tedge/plugins/ot/ layout, so a config, a flow or a cloud integration built against one works unchanged against the other. They conflict with each other: a host runs one or the other.

Install

1. Set up the thin-edge.io community repository (instructions). It carries tedge-dot-c and its tedge-parameter-plugin dependency, so set it up even when you install a downloaded package.

2. Install the package.

   Debian / Ubuntu

   sudo apt-get install -y tedge-dot-c
   sudo systemctl status tedge-dot

   RPM distros

   sudo dnf install tedge-dot-c

   Downloaded package

   Every release attaches .deb, .rpm and .apk packages and tarballs for amd64, arm64 and armhf, with one SHA256SUMS:

   sudo apt-get install -y ./tedge-dot-c_*_amd64.deb

   The package depends on libmodbus5, libmosquitto1 and libcjson1 (Debian/Ubuntu names); open62541 is statically linked.

3. Add devices. The service starts with no devices configured. Add [[device]] sections to the configs in /etc/tedge/plugins/ot/, or copy a demo config from /usr/share/tedge-dot/demo/. The change is applied within a few seconds, without a restart.

Alpine

The attached .apk files carry a version string that apk-tools rejects, so use the tarball on Alpine for now. The tarball holds the binary (which doubles as a one-shot read/write CLI), the default configs in config-defaults/ and the device-side flows:

./tedge-dot read -c config-defaults/modbus.toml --json

Where it differs

The parity table in the C implementation reference is the single source of truth. Each gap is declared in the build and enforced by test tags, so a test that needs a missing capability is reported as skipped for the C build rather than quietly passing. In short, tedge-dot-c does not have:

• SNMPv3 with SHA-2 authentication or AES-192/256 privacy. MD5/SHA with DES/AES works. A device configured with one of the others stays disconnected with a reason naming the capability, while every other device keeps working.
• The deprecated Basic128Rsa15 OPC UA policy. Basic256 and the current policies work.
• CAN FD frames: classic CAN only.
• PROFIBUS-DP on a serial line. It speaks tcp:// to a device server or the simulator.

Two behaviours differ as well: a wedged protocol call (stall_timeout) restarts the whole process rather than one connector, and string values are capped at 255 bytes, bytes values at 127 bytes and raw values at 256 bytes. A bytes value or an OPC UA structure body over its limit is a bad sample that names the limit, never a truncated value. See Liveness and Known limitations.

Need PROFIBUS-DP?

The C package is the one that ships the PROFIBUS-DP connector. The Rust package omits it, because its serial dependency does not cross-compile; build tedge-dot-rs from source with --features profibus on Linux if you need it there.

The PROFIBUS-DP connector is a preview: it is tested against a DP slave simulator, not yet on real equipment.

Next steps

InstallEvery install route, upgrading, and moving from the old package name.

Package pickerA recommendation for your gateway, with the reasons.

C implementationParity table, cross-compilation, size comparison and licensing.

Reducing data volumeSmall gateways often sit on metered links too.