diff --git a/zk/Debian_package_management.md b/zk/Debian_package_management.md
index c312caa..68f50bb 100644
--- a/zk/Debian_package_management.md
+++ b/zk/Debian_package_management.md
@@ -6,6 +6,8 @@ tags:
 
 # Debian package management
 
+> Can now actually do away with `apt-get` and just use `apt`
+
 ## Update and install package
 
 ```sh
@@ -23,4 +25,12 @@ sudo apt-get update
 
 ```sh
 sudo apt autoremove <package_name>
+`
+
+```
+
+## List installed packages
+
+```
+apt list --installed
 ```
diff --git a/zk/mosquitto_mqtt_client.md b/zk/mosquitto_mqtt_client.md
new file mode 100644
index 0000000..5bfc802
--- /dev/null
+++ b/zk/mosquitto_mqtt_client.md
@@ -0,0 +1,67 @@
+---
+tags:
+  - Linux
+  - Debian
+  - mqtt
+---
+
+## Config
+
+At `/etc/mosquitto/mosquitto.conf`.
+
+Most important lines:
+
+```
+listener 1883
+allow_anonymous true
+```
+
+This means `mosquitto` will run on port:1883 and that I am not using
+authentication with requests to the broker.
+
+### Websockets
+
+In order to enable [websockets](./Web_sockets.md), must create a config file at
+`/etc/mosquitto/mosquitto.conf/websockets.conf`:
+
+```
+# /etc/mosquitto/mosquitto.conf/websockets.conf`
+listener 8083
+protocol websockets
+```
+
+This is only relevant if you require access from outside of the local network.
+
+## Basic usage
+
+## Create a topic
+
+```sh
+mosquitto_sub -d -t test_topic
+```
+
+This then enters listening mode and takes control of terminal:
+
+```
+$ mosquitto_sub -d -t test_topic
+Client (null) sending CONNECT
+Client (null) received CONNACK (0)
+Client (null) sending SUBSCRIBE (Mid: 1, Topic: test_topic, QoS: 0, Options: 0x00)
+Client (null) received SUBACK
+Subscribed (mid: 1): 0
+```
+
+## Publish to a topic
+
+From my other machine I install `mosquitto` and:
+
+```sh
+mosquitto_pub --host 192.168.68.53 --port 1883 --topic test_topic --message 'hello world'
+```
+
+This registers on the broker device:
+
+```
+Client (null) received PUBLISH (d0, q0, r0, m0, 'test_topic', ... (11 bytes))
+hello world
+```