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FAQ.md

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+
+### Performance 
+
+#### JVM startup
+Every invocation of `signal-cli ...` starts a Java Virtual Machine instance. This can take anywhere from a second to many time over that, depending on the system. 
+
+To avoid it, signal-cli can be started as a daemon, with subsequent commands sent to it through DBus. See [using `dbus-send`](https://github.com/AsamK/signal-cli/wiki/DBus-service#user-content-send-using-dbus-send).
+
+There is a also an experimental native library build using GraalVM that avoids JVM startup. See [GraalVM section in README](https://github.com/AsamK/signal-cli/blob/master/README.md#user-content-building-a-native-binary-with-graalvm-experimental)
+
+
+#### System entropy
+
+Some signal-cli's operations require that enough system entropy / randomness is available.  
+
+Available entropy can be monitored with
+
+	watch cat /proc/sys/kernel/random/entropy_avail 
+
+If it is hitting zero during `signal-cli ...` execution, signal-cli will block until enough entropy is available. 
+
+System entropy is more likely to get depleted on headless servers. There are programs that allow to increase the amount of available entropy, e.g. [`haveged`](http://issihosts.com/haveged/).
+
+
+#### See also
+[#351](https://github.com/AsamK/signal-cli/issues/351#issuecomment-694871183) with links to past discussions.  
+
+
+### Error parsing arguments
+
+	$ signal-cli receive --output=json
+	signal-cli: error: unrecognized arguments: '--output=json'
+
+The `--output=...` option needs to be in front of the `receive` subcommand: 
+
+	$ signal-cli --output=json receive 
+
+This is [Argparse4j](https://argparse4j.github.io/)'s behavior.
+
+
+### DBus errors when starting daemon
+See [Troubleshooting DBus](https://github.com/AsamK/signal-cli/wiki/DBus-service#user-content-troubleshooting).