Editing OpenSearch Cluster Installation (section)

== Node Preparation ==
Each node to be used in the cluster must be prepared to support the OpenSearch installation.

=== Create Opensearch User ===
Debian/Ubuntu:
 sudo adduser --system -uid 968 --shell /bin/bash --gecos 'OpenSearch User'  --group  --disabled-password --home /opt/opensearch opensearch
Fedora/RHEL:
 sudo adduser --system --uid 968 --shell /bin/bash --home-dir /opt/opensearch -m opensearch
Then add your normal user to the group:
 sudo usermod -aG opensearch ewilliam

=== Set vm.max_map_count ===
Create <code>/etc/sysctl.d/vm.maxmap_count.conf</code> (as root) and add the following line:
 vm.max_map_count=262144
Run the following command as root to load the new configuration:
 sysctl --system

=== Systemd Unit File ===
One of the big things missing from the tarball distribution is a systemd unit file.  Fortunately, it isn't difficult to create a simple one that will work.

Create a file <code>/etc/systemd/system/opensearch.service</code> with the following contents:
 [Unit]
 Description=OpenSearch
 Documentation=<nowiki>https://opensearch.org/docs/</nowiki>
 Wants=network-online.target
 After=network-online.target
 
 [Service]
 Type=exec
 RuntimeDirectory=opensearch
 PrivateTmp=true
 Environment=OPENSEARCH_HOME=/opt/opensearch/opensearch
 Environment=OPENSEARCH_PATH_CONF=/opt/opensearch/opensearch/config
 Environment=PID_DIR=/opt/opensearch/opensearch
 Environment=OPENSEARCH_SD_NOTIFY=true
 EnvironmentFile=-/opt/opensearch/opensearch/opensearch.env
 
 WorkingDirectory=/opt/opensearch/opensearch
 
 User=opensearch
 Group=opensearch
 
 ExecStart=/opt/opensearch/opensearch/bin/opensearch -p ${PID_DIR}/opensearch.pid --quiet
 
 # StandardOutput is configured to redirect to journalctl since
 # some error messages may be logged in standard output before
 # elasticsearch logging system is initialized. Elasticsearch
 # stores its logs in /var/log/elasticsearch and does not use
 # journalctl by default. If you also want to enable journalctl
 # logging, you can simply remove the "quiet" option from ExecStart.
 StandardOutput=journal
 StandardError=inherit
 
 # Specifies the maximum file descriptor number that can be opened by this process
 LimitNOFILE=65535
 
 # Specifies the maximum number of processes
 LimitNPROC=4096
 
 # Specifies the maximum size of virtual memory
 LimitAS=infinity
 
 # Specifies the maximum file size
 LimitFSIZE=infinity
 
 # Disable timeout logic and wait until process is stopped
 TimeoutStopSec=0
 
 # SIGTERM signal is used to stop the Java process
 KillSignal=SIGTERM
 
 # Send the signal only to the JVM rather than its control group
 KillMode=process
 
 # Java process is never killed
 SendSIGKILL=no
 
 # When a JVM receives a SIGTERM signal it exits with code 143
 SuccessExitStatus=143
 
 # Allow a slow startup before the systemd notifier module kicks in to extend the timeout
 TimeoutStartSec=75
 
 [Install]
 WantedBy=multi-user.target