Solr scripts for cloud example break if called from a directory other than $SOLR_HOME, ie $PWD is not $SOLR_HOME: It always strips off the beginning of the path. This used to work regardless in Solr 4.x as I used to use it quite a lot and my custom solr 4.x docker containers it still works regardless of $PWD - it's only broken in 5x/6.0.
Here is an example of the issue:
docker run -ti solr bash
solr@5083b8e59d49:/opt/solr$ cd /
solr@5083b8e59d49:/$ solr -e cloud
Welcome to the SolrCloud example!
This interactive session will help you launch a SolrCloud cluster on your local workstation.
To begin, how many Solr nodes would you like to run in your local cluster? (specify 1-4 nodes) :
Ok, let's start up 2 Solr nodes for your example SolrCloud cluster.
Please enter the port for node1 :
Please enter the port for node2 :
Creating Solr home directory /opt/solr/example/cloud/node1/solr
Cloning /opt/solr/example/cloud/node1 into
Starting up Solr on port 8983 using command:
/opt/solr/bin/solr start -cloud -p 8983 -s "pt/solr/example/cloud/node1/solr"
Solr home directory pt/solr/example/cloud/node1/solr not found!
ERROR: Process exited with an error: 1 (Exit value: 1)