+```bash
+gradle shadowJar -PJAVA_VERSION=1.8
+```
+
+When using `-PJAVA_VERSION=1.8` the libraries from `j8lib` (instead of `j11lib`) will be used in the compile
+and runtime classpath and also used in the `makeDist` build step. Where a Java version of `11` is used in folder and file names, it will
+instead use `1.8`. Also if you are building installer packages with *install4j* the
+package builder will look for JRE 1.8 bundles to package in the installers.
+
+> Note that continued development of Jalview will assume a Java 11+ runtime environment,
+the 2.11.0 release will run under a Java 1.8 JRE with a few minor features disabled.
+
+#### `CHANNEL`
+This changes the `appbase` setting in `getdown.txt` (`appbase` is where the getdown launcher
+looks to see if there's an updated file) to point to a particular Jalview channel or some other appropriate
+place to look for required files. If the selected channel type requires the getdown `appbase` to be a local
+directory on the filesystem (instead of a website URL) then a modified version of the `getdown-launcher.jar` will
+be used to allow this. The two versions of the `getdown-launcher.jar` can be found in `getdown/lib`.
+Some other variables used in the build process might also be set differently depending on the value of `CHANNEL`
+to allow smooth operation of getdown in the given context.
+
+There are several values of `CHANNEL` that can be chosen, with a default of `LOCAL`. Here's what they're for and what they do:
+
+* `LOCAL`: This is for running the compiled application from the development directory.
+ It will set
+ - `appbase` as `file://PATH/TO/YOUR/DEVELOPMENT/getdown/files/JAVA_VERSION`
+ (e.g. `file://home/user/git/jalview/getdown/files/11`)
+ - application subdir as `alt`
+ - Getdown launcher can use a `file://` scheme appbase.
+* `BUILD`: This is for creating an appbase channel on the build server by an automatic or manually started build.
+ It will set
+ - `appbase` as `https://builds.jalview.org/browse/${bamboo_planKey}/latest/artifact/shared/getdown-channel/JAVA_VERSION`
+ Note that bamboo_planKey should be set by the build plan with `-Pbamboo_planKey=${bamboo.planKey}`
+ - application subdir as `alt`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `DEVELOP`: This is for creating a `develop` appbase channel on the main web server. This won't become live until the actual getdown artefact is synced to the web server.
+ It will set
+ - `appbase` as `http://www.jalview.org/getdown/develop/JAVA_VERSION`
+ - application subdir as `alt`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `SCRATCH-NAME`: This is for creating a temporary scratch appbase channel on the main web server. This won't become live until the actual getdown artefact is synced to the web server. This is meant for testing an over-the-air update without interfering with the live `release` or `develop` channels. The value of `NAME` can be any "word-character" [A-Za-z0-9\_]
+ It will set
+ - `appbase` as `http://www.jalview.org/getdown/SCRATCH-NAME/JAVA_VERSION`
+ - application subdir as `alt`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `TEST-LOCAL`: Like `SCRATCH` but with a specific `test-local` channel name and a local filesystem appbase. This is meant for testing an over-the-air update on the local filesystem. An extra property `LOCALDIR` must be given (e.g. `-PLOCALDIR=/home/user/tmp/test`)
+ It will set
+ - `appbase` as `file://${LOCALDIR}`
+ - application subdir as `alt`
+ - Getdown launcher can use a `file://` scheme appbase.
+* `TEST-RELEASE`: Like `SCRATCH` but with a specific `test-release` channel name. This won't become live until the actual getdown artefact is synced to the web server. This is meant for testing an over-the-air update without interfering with the live `release` or `develop` channels.
+ It will set
+ - `appbase` as `http://www.jalview.org/getdown/test-release/JAVA_VERSION`
+ - application subdir as `alt`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `RELEASE`: This is for an actual release build, and will use an appbase on the main web server with the main `release` channel name. This won't become live until the actual getdown artefact is synced to the web server.
+ It will set
+ - `appbase` as `http://www.jalview.org/getdown/release/JAVA_VERSION`
+ - application subdir as `release`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `ARCHIVE`: This is a helper to create a channel for a specific release version, and will use an appbase on the main web server with a specific `archive/JALVIEW_VERSION` channel name. This won't become live until the actual getdown artefact is synced to the web server.
+You must also specify an `ARCHIVEDIR` property that points to an earlier version of Jalview with a `dist` directory containing the required jar files. This should create a getdown structure and digest with the older jar files.
+ It will set
+ - `appbase` as `http://www.jalview.org/getdown/archive/JALVIEW_VERSION/JAVA_VERSION`
+ - application subdir as `alt`
+ - Getdown launcher cannot use a `file://` scheme appbase.
+* `ARCHIVELOCAL`: Like `ARCHIVE` but with a local filesystem appbase for local testing.
+You must also specify an `ARCHIVEDIR` property that points to an earlier version of Jalview with a `dist` directory containing the required jar files. This should create a getdown structure and digest with the older jar files.
+ It will set
+ - `appbase` as `file://PATH/TO/YOUR/DEVELOPMENT/getdown/website/JAVA_VERSION` (where the old jars will have been copied and digested)
+ - application subdir as `alt`
+ - Getdown launcher can use a `file://` scheme appbase.
+
+e.g.
+```bash
+gradle getdown -PCHANNEL=SCRATCH-my_test_version
+```
+
+#### `install4jMediaTypes`
+If you are building *install4j* installers (requires *install4j* to be installed) then this property specifies a comma-separated
+list of media types (i.e. platform specific installers) *install4j* should actually build.
+
+Currently the valid values are
+`linuxDeb`,
+`linuxRPM`,
+`macosArchive`,
+`unixArchive`,
+`unixInstaller`,
+`windows`