Having problem when trying to start Search Server.

Hi,

We are using version 22.2.425.0.

We had to restart Appian, so stoped it and tried to restart it  following the Appian Documentation (https://docs.appian.com/suite/help/22.1/Linux_Installation_Guide.html#part-3-startup-and-setup).

The problem occured when trying to start the Search Server

START search server BEGIN
+ [[ '' == \-\f ]]
+ [[ '' == \-\-\f\o\r\e\g\r\o\u\n\d ]]
+ SS_TMP=/app/appian/search-server/tmp
+ mkdir -p /app/appian/search-server/tmp
+ ES_PATH_CONF=/app/appian/search-server/conf
+ ES_JAVA_OPTS='-Xloggc:/tmp/gc.log -XX:NumberOfGCLogFiles=1 -XX:GCLogFileSize=1m -Djava.net.preferIPv4Stack=true -Duser.timezone=GMT -Djna.tmpdir=/app/appian/search-server/tmp'
+ ES_TMPDIR=/app/appian/search-server/tmp
+ /app/appian/search-server/elasticsearch/bin/elasticsearch -Eaction.auto_create_index=false -Ecluster.initial_master_nodes=localhost -Ecluster.name=appian-search-cluster -Ecluster.routing.allocation.disk.watermark.flood_stage=500mb -Ecluster.routing.allocation.disk.watermark.high=500mb -Ecluster.routing.allocation.disk.watermark.low=500mb -Ediscovery.seed_hosts=localhost:9300 -Ehttp.port=9200 -Eindices.fielddata.cache.size=15% -Enetwork.bind_host=0.0.0.0 -Enetwork.publish_host=localhost -Enode.name=localhost -Epath.data=/app/appian/search-server/data -Epath.logs=/app/appian/logs/search-server -Ethread_pool.write.queue_size=500 -Etransport.tcp.port=9300 -Etransport.type=netty4 --pidfile=/app/appian/search-server/bin/ss.pid --daemonize
warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME
Future versions of Elasticsearch will require Java 11; your Java version from [/home/app/appian/java/jre] does not meet this requirement. Consider switching to a distribution of Elasticsearch with a bundled JDK. If you are already using a distribution with a bundled JDK, ensure the JAVA_HOME environment variable is not set.
warning: no-jdk distributions that do not bundle a JDK are deprecated and will be removed in a future release
warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME
Future versions of Elasticsearch will require Java 11; your Java version from [/home/app/appian/java/jre] does not meet this requirement. Consider switching to a distribution of Elasticsearch with a bundled JDK. If you are already using a distribution with a bundled JDK, ensure the JAVA_HOME environment variable is not set.
warning: no-jdk distributions that do not bundle a JDK are deprecated and will be removed in a future release
+ set +x
Attempt 1/6: Waiting 5 seconds for Appian Search Server to start ...
uncaught exception in thread [main]
java.lang.RuntimeException: can not run elasticsearch as root
        at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:107)
        at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:183)
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:434)
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:166)
        at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:157)
        at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:77)
        at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:112)
        at org.elasticsearch.cli.Command.main(Command.java:77)
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:122)
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:80)
For complete error details, refer to the log at /app/appian/logs/search-server/appian-search-cluster.log
Attempt 2/6: Waiting 5 seconds for Appian Search Server to start ...
Attempt 3/6: Waiting 5 seconds for Appian Search Server to start ...
Attempt 4/6: Waiting 5 seconds for Appian Search Server to start ...
Attempt 5/6: Waiting 5 seconds for Appian Search Server to start ...
Attempt 6/6: Waiting 5 seconds for Appian Search Server to start ...
ERROR: Unable to start Appian Search Server.
START search server END
=========================================================
START tomcat BEGIN
Tomcat log rotation enabled via /sbin/rotatelogs
START tomcat END
=========================================================

The ERROR says "ERROR: Unable to start Appian Search Server."

and it is also written to "For complete error details, refer to the log at /app/appian/logs/search-server/appian-search-cluster.log"

But, there is no such log file in the following directory.

How can I fix this problem?

P.S. Could the warning message syaing "warning: usage of JAVA_HOME is deprecated, use ES_JAVA_HOME" be relevant with the problem?