==== Running Elasticsearch with `systemd`

To configure Elasticsearch to start automatically when the system boots up,
run the following commands:

[source,sh]
--------------------------------------------------
sudo /bin/systemctl daemon-reload
sudo /bin/systemctl enable elasticsearch.service
--------------------------------------------------

Elasticsearch can be started and stopped as follows:

[source,sh]
--------------------------------------------
sudo systemctl start elasticsearch.service
sudo systemctl stop elasticsearch.service
--------------------------------------------

These commands provide no feedback as to whether Elasticsearch was started
successfully or not. Instead, this information will be written in the log
files located in `/var/log/elasticsearch/`.

If you have password-protected your {es} keystore, you will need to provide
`systemd` with the keystore password using a local file and systemd environment
variables. This local file should be protected while it exists and may be
safely deleted once Elasticsearch is up and running.

[source,sh]
-----------------------------------------------------------------------------------
echo "keystore_password" > /path/to/my_pwd_file.tmp
chmod 600 /path/to/my_pwd_file.tmp
sudo systemctl set-environment ES_KEYSTORE_PASSPHRASE_FILE=/path/to/my_pwd_file.tmp
sudo systemctl start elasticsearch.service
-----------------------------------------------------------------------------------

By default the Elasticsearch service doesn't log information in the `systemd`
journal. To enable `journalctl` logging, the `--quiet` option must be removed
 from the `ExecStart` command line in the `elasticsearch.service` file.

When `systemd` logging is enabled, the logging information are available using
the `journalctl` commands:

To tail the journal:

[source,sh]
--------------------------------------------
sudo journalctl -f
--------------------------------------------

To list journal entries for the elasticsearch service:

[source,sh]
--------------------------------------------
sudo journalctl --unit elasticsearch
--------------------------------------------

To list journal entries for the elasticsearch service starting from a given time:

[source,sh]
--------------------------------------------
sudo journalctl --unit elasticsearch --since  "2016-10-30 18:17:16"
--------------------------------------------

Check `man journalctl` or https://www.freedesktop.org/software/systemd/man/journalctl.html for
more command line options.
