I have the same issue after reinstalling on macOS with Homebrew:
elasticsearch
Java HotSpot(TM) 64-Bit Server VM warning: Cannot open file logs/gc.log due to No such file or directory
[2019-04-01T11:03:23,837][INFO ][o.e.e.NodeEnvironment ] [KQayVM1] using [1] data paths, mounts [[/ (/dev/disk1s1)]], net usable_space [951.2gb], net total_space [1.8tb], types [apfs]
[2019-04-01T11:03:23,852][INFO ][o.e.e.NodeEnvironment ] [KQayVM1] heap size [989.8mb], compressed ordinary object pointers [true]
[2019-04-01T11:03:23,864][INFO ][o.e.n.Node ] [KQayVM1] node name derived from node ID [KQayVM1ZTRWVQfJbgrnbTQ]; set [node.name] to override
[2019-04-01T11:03:23,864][INFO ][o.e.n.Node ] [KQayVM1] version[6.7.0], pid[11489], build[oss/tar/8453f77/2019-03-21T15:32:29.844721Z], OS[Mac OS X/10.14.4/x86_64], JVM[Oracle Corporation/Java HotSpot(TM) 64-Bit Server VM/1.8.0_192/25.192-b12]
[2019-04-01T11:03:23,864][INFO ][o.e.n.Node ] [KQayVM1] JVM arguments [-Xms1g, -Xmx1g, -XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -Des.networkaddress.cache.ttl=60, -Des.networkaddress.cache.negative.ttl=10, -XX:+AlwaysPreTouch, -Xss1m, -Djava.awt.headless=true, -Dfile.encoding=UTF-8, -Djna.nosys=true, -XX:-OmitStackTraceInFastThrow, -Dio.netty.noUnsafe=true, -Dio.netty.noKeySetOptimization=true, -Dio.netty.recycler.maxCapacityPerThread=0, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Djava.io.tmpdir=/var/folders/t_/8nf2m8hd56v9v6h2gxzyhbhh0000gn/T/elasticsearch-7413103318878119681, -XX:+HeapDumpOnOutOfMemoryError, -XX:HeapDumpPath=data, -XX:ErrorFile=logs/hs_err_pid%p.log, -XX:+PrintGCDetails, -XX:+PrintGCDateStamps, -XX:+PrintTenuringDistribution, -XX:+PrintGCApplicationStoppedTime, -Xloggc:logs/gc.log, -XX:+UseGCLogFileRotation, -XX:NumberOfGCLogFiles=32, -XX:GCLogFileSize=64m, -Des.path.home=/usr/local/Cellar/elasticsearch/6.7.0/libexec, -Des.path.conf=/usr/local/etc/elasticsearch, -Des.distribution.flavor=oss, -Des.distribution.type=tar]
[2019-04-01T11:03:23,905][WARN ][o.e.b.ElasticsearchUncaughtExceptionHandler] [KQayVM1] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalStateException: Duplicate key org.elasticsearch.plugins.PluginsService$Bundle@dfcd13ae
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:163) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:150) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.7.0.jar:6.7.0]
at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:116) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:93) ~[elasticsearch-6.7.0.jar:6.7.0]
Caused by: java.lang.IllegalStateException: Duplicate key org.elasticsearch.plugins.PluginsService$Bundle@dfcd13ae
at java.util.stream.Collectors.lambda$throwingMerger$0(Collectors.java:133) ~[?:1.8.0_192]
at java.util.HashMap.merge(HashMap.java:1254) ~[?:1.8.0_192]
at java.util.stream.Collectors.lambda$toMap$58(Collectors.java:1320) ~[?:1.8.0_192]
at java.util.stream.ReduceOps$3ReducingSink.accept(ReduceOps.java:169) ~[?:1.8.0_192]
at java.util.Iterator.forEachRemaining(Iterator.java:116) ~[?:1.8.0_192]
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801) ~[?:1.8.0_192]
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481) ~[?:1.8.0_192]
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471) ~[?:1.8.0_192]
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708) ~[?:1.8.0_192]
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) ~[?:1.8.0_192]
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499) ~[?:1.8.0_192]
at org.elasticsearch.plugins.PluginsService.sortBundles(PluginsService.java:420) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:466) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:163) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.node.Node.<init>(Node.java:339) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.node.Node.<init>(Node.java:266) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:212) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:212) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:333) ~[elasticsearch-6.7.0.jar:6.7.0]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-6.7.0.jar:6.7.0]
... 6 more