there is an officially supported mechanism to add hostnames in Travis CI

Author: vroldanbet

.travis.yml

@@ -9,6 +9,10 @@ rvm:
   - jruby-head
   - rbx-2
 
+addons:
+  hosts:
+    - ldap.example.org # needed for TLS verification
+
 services:
   - docker
 
@@ -17,7 +21,6 @@ env:
 
 before_install:
   - gem update bundler
-  - echo "127.0.0.1 ldap.example.org" >> /etc/hosts # needed for TLS verification
 
 install:
   - docker run --hostname ldap.example.org --env LDAP_TLS_VERIFY_CLIENT=try -p 389:389 -p 636:636 -v $(pwd)/test/fixtures/seed.ldif:/container/service/slapd/assets/config/bootstrap/ldif/50-bootstrap.ldif --name openldap osixia/openldap:1.3.0 --copy-service --loglevel debug