Install Eclipse Mosquitto MQTT on a Raspberry Pi 3B Running Raspbian Stretch

Transcription

1 Install Eclipse Mosquitto MQTT on a Raspberry Pi 3B Running Raspbian Stretch October 7, 2017 David Dickinson, eveningstarnm@gmail.com Eclipse Mosquitto ( is a popular open-source implementation of the MQTT protocol for Linux embedded devices and low power machines. It runs well on Raspbian Jessie devices. But with the release of the Debian Stretch-based version of Raspbian, the popular operating system for Raspberry Pis, installing Mosquitto from the repository or by the usual build-from-source methods doesn t work. The current version that is available from the Raspbian repository contains references to dependencies that cause installation to fail. This guide describes how to overcome these problems and get Mosquitto up and running on your Raspbian Stretch-based Raspberry Pi. WARNING: At the time of this writing, you should not be running a version of Eclipse Mosquitto older than due to a security issue in earlier versions. See CVE at The Problem Users who were running Raspbian Jessie when they installed Mosquitto and who then upgraded to Stretch have no problems. The problems occur on fresh installations of Raspbian Stretch or on devices on which Mosquitto had not been previously installed, even if they were upgraded from Jessie to Stretch: $ sudo apt-get install mosquitto Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: mosquitto : Depends: libssl1.0.0 (>= 1.0.1) but it is not installable Depends: libwebsockets3 (>= 1.2) but it is not installable You cannot install libssl1.0.0 or libwebsockets3 because they aren t available in the repository. Besides, especially for OpenSSL, you always want to be running the latest versions, which at the time of this writing are v1.0.2 (the newest long term support version) and (the latest stable version). WARNING: At the time of this writing, you should not be running versions of OpenSSL older than 1.0.2m (LTS version) or 1.1.0g (stable version). See CVE at

2 For websockets, the version available in the Raspbian repo is libwebsockets8, but the attempt to install Mosquitto fails because it is looking for libwebsockets3. Both of these problems exist because the developers of those dependencies included the version in the name of the package, such as libssl1.0.0 instead of simply libssl. Dependent packages, which would otherwise work very well with newer versions of the code, search for a name containing numerals, but deprecated versions have been removed from the repositories. A similar problem exists if you try to install the mosquitto-clients package: $ sudo apt install mosquitto-clients Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: mosquitto-clients : Depends: libmosquitto1 (= mosquitto1) but it is not going to be installed E: Unable to correct problems, you have held broken packages. Here, the dependency is on libmosquitto1, which cannot be installed because of dependencies on libcares2, as well as on libssl1.0.0, which is discussed above. The package libc-ares2 is actually available in the repository and can be installed separately. (We will not investigate why this error appears.) Prerequisites First of all, you must decide if you want support for web sockets in your MQTT installation. There are two versions of mosquitto, libmosquitto1, and mosquitto-clients that will be explained here: v which has support for web sockets v which does not support web sockets ( ~nows1 appears in the filenames) If you re planning on subscribing or publishing to MQTT using Javascript, you want web sockets. You must also decide which version of OpenSSL you are or will be using. There are two series: the longterm service series, which is currently at v1.0.2, and the stable series, now at version 1.1. Fixing The Broker We ll work on the mosquitto broker first. Follow these steps: Create a work folder. For this example, we will use /home/pi/mosquitto: $ mkdir mosquitto $ cd mosquitto

3 Download the latest version. Aside from the development and debug versions, you ll see two versions of the broker for armhf devices shown at the repo, which is at One version, v1.4.12, has support for web sockets. Version , however, does not, as indicated by the ~nows1 in the filename. We ll cover fixing both versions here, so we need to download both of them. You should download only the one that you need. wget # Supports web sockets or, if you don t need web sockets support: wget # Does NOT support web sockets We ll create new subdirectories for working on the broker, one for the version with web sockets support and one without it, and extract the raw contents of the package into them: or mkdir brokerws dpkg-deb R mosquitto_ mosquitto1_armhf.deb brokerws mkdir brokernows dpkg-deb R mosquitto_ mosquitto1~nows1_armhf.deb brokernows Now we must edit the control file to fix the reference to the non-existent dependency. or nano brokerws/debian/control nano brokernows/debian/control For the version supporting web sockets, in the line beginning with Depends: are the two entries that we re concerned with here: libssl1.0.0 (>= 1.0.1) libwebsockets3 (>= 1.2) If you re using the long-term support branch of OpenSSL, then you should change the dependency to libssl1.0.2 (>= 1.0.2). For the stable version, change it to libssl1.1 (>= 1.1). IMPORTANT: The versions of libssl that are available in the repository are NOT patched for CVE This article assumes that you re maintaining them yourself. If you re reading this when the versions given here are removed from the repository and replaced with newer versions, make changes to the above entries that are appropriate.

4 Similarly, change the web sockets library entry to libwebsockets8 (>= 2.0.3). If you re working on mosquitto v without web sockets support, you can skip this step. Make a note of the other dependencies. We ll have to make sure that they re installed later. Save the file with CTRL-x and exit nano. Now we want to repackage the fixed version: Or $ dpkg-deb b brokerws mosquitto_ mosquitto1_armhf-fixed.deb $ dpkg-deb b brokernows mosquitto_ mosquitto1~nows1_armhf-fixed.deb You can now delete the original files and the broker* folder. Fixing the Mosquitto Library The library and client packages for Mosquitto, libmosquitto1 and mosquitto-clients, both suffer from the same dependencies. As well, there are two versions of interest, v with web sockets support, and v without it. However, it is not necessary to make any changes to mosquitto-clients, since its installation fails only because the installation of its dependency fails. When libmosquitto1 is fixed, the client can be installed successfully. The procedures for fixing the errant dependency in libmosquitto1 are the same as those given above for the broker: Change the dependency on libssl1.0.0 (>= 1.0.0) to either the long-term service version or the stable version that actually exists in the repository. USE THE SAME VERSION THAT YOU USED FOR THE BROKER, ABOVE. In addition, make sure that you use the correct version of the library for the version of the broker that you want to install, either Mosquitto v or v Installation Make sure that you have Openssl (libssl1.1 or libssl1.0.2) installed. Install the version that you specified in the control file. We must also make sure that these other dependencies are installed. You can check if what you have installed or what is available using this command: sudo apt-cache policy <package name> adduser (>= 3.10) (At least version may be already installed.) libuuid1 (>= 2.16) (At least version may be already installed.) lsb-base (>=4.1+Debian3) (At least version rpi1 may be already installed.) libwebsockets8 (>= 2.0.3) (if you need it for Mosquitto only) libwrap0 (>= 7.6.4~) (At least version 7.6.q-26 may be installed. This should work.) libc-ares2 (>= 1.7.0) (You may have to install it.) libc6 (>= 2.15) (At least version deb9u1 may already be installed.)

5 You must install the version of libmosquitto1 that is appropriate to the version of mosquitto and mosquitto-clients that you re going to install, and that depends on whether or not you need web sockets support. Pick one version for all three, either v or v Don t mix versions. Install the fixed packages using this command: sudo dpkg i <filename> Select the packages by version number, using v if you need web sockets support, or v if you don t. Install the packages in this order: 1. libmosquitto1 2. mosquitto 3. mosquitto-clients (We ll use them to test the installation.) Testing Now, we can test the installation. Open a terminal window (we ll be using three terminal windows) and do the following: $ sudo /etc/init.d/mosquitto stop [ ok ] Stopping mosquitto (via systemctl): mosquitto.service. $ sudo /etc/init.d/mosquitto start [ ok ] Starting mosquitto (via systemctl): mosquitto.service. $ mosquitto v Now, in a new terminal window, we ll subscribe to the topic hellow/world : $ mosquitto_sub -d -t hello/world Back in the first terminal window, we ll publish a message: $ mosquitto_pub -d -t hello/world -m "Hello from Mosquitto!" Go back to the subscription window, and you should see something similar to the following: $ mosquitto_sub -d -t hello/world Client mosqsub 1154-raspi3 sending CONNECT Client mosqsub 1154-raspi3 received CONNACK Client mosqsub 1154-raspi3 sending SUBSCRIBE (Mid: 1, Topic: hello/world, QoS: 0) Client mosqsub 1154-raspi3 received SUBACK Subscribed (mid: 1): 0 Client mosqsub 1154-raspi3 received PUBLISH (d0, q0, r0, m0, 'hello/world',... (21 bytes)) Hello from Mosquitto! Client mosqsub 1154-raspi3 sending PINGREQ Client mosqsub 1154-raspi3 received PINGRESP If you see Hello from Mosquitto!, then your installation is working correctly, and it s time for a sandwich.