Hi, Harmanjeet.
I believe Yuriy miss-typed, you indeed need to edit this file in `/opt/gluu/jetty/identity/webapps/identity.war` You need to unpack the file from that archive, edit it, and pack it back into it.
Can be done with tool `jar` already present in container:
1. Stop the corresponding service: `# service identity stop`
2. Create a temp directory to work with the archive: `# mkdir ~/identity_unpacked/; cd ~/identity_unpacked/`
3. Find relative path to the file in WAR: `# /opt/jre/bin/jar -tf /opt/gluu/jetty/identity/webapps/identity.war | grep -i 'oxtrust_en.properties'`
4. Unpack the file you need: `# /opt/jre/bin/jar -xf /opt/gluu/jetty/identity/webapps/identity.war WEB-INF/classes/oxtrust_en.properties`
5. Modify it in place where it was unpacked: `# vim WEB-INF/classes/oxtrust_en.properties`
6. Place the updated file back into archive, overwriting the old one: `# /opt/jre/bin/jar -uf /opt/gluu/jetty/identity/webapps/identity.war WEB-INF/classes/oxtrust_en.properties`
7. Start the corresponding service: `# service identity start`