Are you creating / adding custom Base Resources?
Then you should use the techniques outlined by Lachlan, albeit with a slight change, as you are using ee8. (Lachlans recommendations work with ee10, and ee11, and all future ee revisions, the older ee8 needs one extra step)
Or are you just serving standard static content from your `<Set name="war">/run/schroot/mount/dev/usr/share/css-validator/css-validator</Set>` path?
Then you'll have an easier time just configuring the DefaultServlet to allow aliases and/or symlinks
In either file ...
* /run/schroot/mount/dev/usr/share/css-validator/css-validator/WEB-INF/web.xml
* /path/to/jetty-base/etc/ee8-webdefault.xml
``` xml
```
If you want to stick with the Jetty XML deployable configuration, use this instead ...
``` xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "
https://www.eclipse.org/jetty/configure_10_0.dtd">
<Configure id="CssValidatorContext" class="org.eclipse.jetty.ee8.webapp.WebAppContext">
<!-- (snip other content here) -->
<!-- get a ContextHandler reference that the AliasChecker can use -->
<Get id="contextHandler" name="coreContextHandler" />
<!-- Enable symlinks -->
<Call name="addAliasCheck">
<Arg>
<New class="org.eclipse.jetty.server.SymlinkAllowedResourceAliasChecker">
<Arg>
<!-- Reference the ContextHandler id you created earlier -->
<Ref refid="contextHandler" />
</Arg>
</New>
</Arg>
</Call>
```