# How to Specifying ES option via Shell environment variables for discovery.zen.ping.unicast.hosts **URL:** \ **Category:** Elasticsearch\ **Created:** [July 25, 2016, 12:59pm UTC](https://discuss.elastic.co/t/how-to-specifying-es-option-via-shell-environment-variables-for-discovery-zen-ping-unicast-hosts/56293 "2016-07-25T12:59:14Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Brad\_Jungsu\_Heo](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/brad_jungsu_heo/32/13135_2.png) [@Brad\_Jungsu\_Heo](https://discuss.elastic.co/u/Brad_Jungsu_Heo)\ **Post date:** [July 25, 2016, 12:59pm UTC](https://discuss.elastic.co/t/how-to-specifying-es-option-via-shell-environment-variables-for-discovery-zen-ping-unicast-hosts/56293/1 "2016-07-25T12:59:14Z")
Hello. I'm using ES 2.3.2 I've decided to use Shell Env. Variables in `elasticsearch.yml` because I want to maintain ONLY 1 `elasticsearch.yml` file even though I have many type of nodes in many clusters. Most of configs are easy to use shell variables. But I turned out that `discovery.zen.ping.unicast.hosts` is weird. **original `elasticsearch.yml`** `discovery.zen.ping.unicast.hosts: ["host1", "host2", "host3"]` **First attempt** I've changed like this: `discovery.zen.ping.unicast.hosts: [${UNICAST_HOSTS}]` And in the shell `export UNICAST_HOSTS='"host1", "host2", "host3"'` But I got an error (Maybe `Invalid Placeholder`? Sorry. I can't remember the exact error message). **Second attemp** - elasticsearch.yml: `discovery.zen.ping.unicast.hosts: ${UNICAST_HOSTS}` - shell: `export UNICAST_HOSTS='["host1", "host2", "host3"']` I got an error as well. **Final Solution** After several trials and errors, I've found that following configuration worked! - elasticsearch.yml: `discovery.zen.ping.unicast.hosts: ${UNICAST_HOSTS}` - shell: `export UNICAST_HOSTS="host1, host2, host3"` It works fine. But where have `[`, `]` gone? Is above configuration is correct? It would be happy if someone tell me "YES" or "NO". I'm not certain because I can't find any authorized documentation. ---
**Author:** ![danielmitterdorfer](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/danielmitterdorfer/32/110510_2.png) [@danielmitterdorfer](https://discuss.elastic.co/u/danielmitterdorfer)\ **Post date:** [July 27, 2016, 11:55am UTC](https://discuss.elastic.co/t/how-to-specifying-es-option-via-shell-environment-variables-for-discovery-zen-ping-unicast-hosts/56293/2 "2016-07-27T11:55:54Z")
Hi @Brad_Jungsu_Heo > [@Brad\_Jungsu\_Heo](#): > > Is above configuration is correct? It would be happy if someone tell me "YES" or "NO". I'm not certain because I can't find any authorized documentation. As far as I can see, the configuration is correct. You can add the following line to `config/logging.yml`: ```auto discovery.zen.ping.unicast: DEBUG ``` This enables debugging logging in the relevant module. On startup you will then see the following line: ```auto [2016-07-27 13:46:52,028][DEBUG][discovery.zen.ping.unicast] [-96ewfK] using initial hosts [host1, host2, host3], with concurrent_connects [10] ``` If this would not get parsed as a list and instead resolved as one host, you should see exceptions traces like this one on startup (which you obviously don't see): ```auto Error injecting constructor, java.lang.IllegalArgumentException: Failed to resolve address for [host1, host2, host3] at org.elasticsearch.discovery.zen.ping.unicast.UnicastZenPing.(Unknown Source) while locating org.elasticsearch.discovery.zen.ping.unicast.UnicastZenPing while locating org.elasticsearch.discovery.zen.ping.ZenPing annotated with @org.elasticsearch.common.inject.multibindings.Element(setName=,uniqueId=1) at _unknown_ while locating java.util.Set for parameter 1 at org.elasticsearch.discovery.zen.ping.ZenPingService.(Unknown Source) while locating org.elasticsearch.discovery.zen.ping.ZenPingService for parameter 5 at org.elasticsearch.discovery.zen.ZenDiscovery.(Unknown Source) while locating org.elasticsearch.discovery.zen.ZenDiscovery while locating org.elasticsearch.discovery.Discovery Caused by: java.lang.IllegalArgumentException: Failed to resolve address for [host1, host2, host3] at org.elasticsearch.discovery.zen.ping.unicast.UnicastZenPing.(UnicastZenPing.java:171) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at [...] Caused by: java.net.UnknownHostException: host1, host2, host3 at java.net.InetAddress.getAllByName0(InetAddress.java:1280) at java.net.InetAddress.getAllByName(InetAddress.java:1192) at java.net.InetAddress.getAllByName(InetAddress.java:1126) at org.elasticsearch.transport.TcpTransport.parse(TcpTransport.java:748) at org.elasticsearch.transport.TcpTransport.addressesFromString(TcpTransport.java:703) at org.elasticsearch.transport.TransportService.addressesFromString(TransportService.java:565) at org.elasticsearch.discovery.zen.ping.unicast.UnicastZenPing.(UnicastZenPing.java:165) ... 60 more ``` Once more: This was just a hypothetical example what _would_ happen if Elasticsearch were not able to resolve this correctly. Daniel ---
**Author:** ![Brad\_Jungsu\_Heo](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/brad_jungsu_heo/32/13135_2.png) [@Brad\_Jungsu\_Heo](https://discuss.elastic.co/u/Brad_Jungsu_Heo)\ **Post date:** [July 28, 2016, 12:43am UTC](https://discuss.elastic.co/t/how-to-specifying-es-option-via-shell-environment-variables-for-discovery-zen-ping-unicast-hosts/56293/3 "2016-07-28T00:43:40Z")
Hi @danielmitterdorfer Thank you so much! ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [July 5, 2017, 10:32pm UTC](https://discuss.elastic.co/t/how-to-specifying-es-option-via-shell-environment-variables-for-discovery-zen-ping-unicast-hosts/56293/4 "2017-07-05T22:32:21Z")