I did sudo chmod -R 750 /var/log/elasticsearch/ and now I get the following messages
/usr/share/elasticsearch$ sudo -u elasticsearch ./bin/elasticsearch
future versions of Elasticsearch will require Java 11; your Java version from [/opt/jdk/jdk1.8.0_202/jre] does not meet this requirement
future versions of Elasticsearch will require Java 11; your Java version from [/opt/jdk/jdk1.8.0_202/jre] does not meet this requirement
[2020-07-23T11:26:56,232][INFO ][o.e.n.Node ] [SERVER1] version[7.8.0], pid[28095], build[default/deb/757314695644ea9a1dc2fecd26d1a43856725e65/2020-06-14T19:35:50.234439Z], OS[Linux/4.15.0-108-generic/amd64], JVM[Oracle Corporation/Java HotSpot(TM) 64-Bit Server VM/1.8.0_202/25.202-b08]
[2020-07-23T11:26:56,233][INFO ][o.e.n.Node ] [SERVER1] JVM home [/opt/jdk/jdk1.8.0_202/jre]
[2020-07-23T11:26:56,233][INFO ][o.e.n.Node ] [SERVER1] JVM arguments [-Xshare:auto, -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, -Dio.netty.allocator.numDirectArenas=0, -Dlog4j.shutdownHookEnabled=false, -Dlog4j2.disable.jmx=true, -Djava.locale.providers=SPI,JRE, -Xms13g, -Xmx13g, -XX:+UseConcMarkSweepGC, -XX:CMSInitiatingOccupancyFraction=75, -XX:+UseCMSInitiatingOccupancyOnly, -Djava.io.tmpdir=/tmp/elasticsearch-6288221564287275426, -XX:+HeapDumpOnOutOfMemoryError, -XX:HeapDumpPath=/var/lib/elasticsearch, -XX:ErrorFile=/var/log/elasticsearch/hs_err_pid%p.log, -XX:+PrintGCDetails, -XX:+PrintGCDateStamps, -XX:+PrintTenuringDistribution, -XX:+PrintGCApplicationStoppedTime, -Xloggc:/var/log/elasticsearch/gc.log, -XX:+UseGCLogFileRotation, -XX:NumberOfGCLogFiles=32, -XX:GCLogFileSize=64m, -XX:MaxDirectMemorySize=6979321856, -Des.path.home=/usr/share/elasticsearch, -Des.path.conf=/etc/elasticsearch, -Des.distribution.flavor=default, -Des.distribution.type=deb, -Des.bundled_jdk=true]
[2020-07-23T11:26:59,128][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [SERVER1] uncaught exception in thread [main]
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalArgumentException: Plugin [ingest-attachment] was built for Elasticsearch version 7.5.0 but version 7.8.0 is running
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:174) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:161) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:127) ~[elasticsearch-cli-7.8.0.jar:7.8.0]
at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:126) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92) ~[elasticsearch-7.8.0.jar:7.8.0]
Caused by: java.lang.IllegalArgumentException: Plugin [ingest-attachment] was built for Elasticsearch version 7.5.0 but version 7.8.0 is running
at org.elasticsearch.plugins.PluginsService.verifyCompatibility(PluginsService.java:348) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.plugins.PluginsService.loadBundle(PluginsService.java:533) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:473) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:164) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.node.Node.<init>(Node.java:317) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.node.Node.<init>(Node.java:266) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:227) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:227) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:393) ~[elasticsearch-7.8.0.jar:7.8.0]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:170) ~[elasticsearch-7.8.0.jar:7.8.0]
... 6 more
uncaught exception in thread [main]
java.lang.IllegalArgumentException: Plugin [ingest-attachment] was built for Elasticsearch version 7.5.0 but version 7.8.0 is running
at org.elasticsearch.plugins.PluginsService.verifyCompatibility(PluginsService.java:348)
at org.elasticsearch.plugins.PluginsService.loadBundle(PluginsService.java:533)
at org.elasticsearch.plugins.PluginsService.loadBundles(PluginsService.java:473)
at org.elasticsearch.plugins.PluginsService.<init>(PluginsService.java:164)
at org.elasticsearch.node.Node.<init>(Node.java:317)
at org.elasticsearch.node.Node.<init>(Node.java:266)
at org.elasticsearch.bootstrap.Bootstrap$5.<init>(Bootstrap.java:227)
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:227)
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:393)
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:170)
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:161)
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86)
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:127)
at org.elasticsearch.cli.Command.main(Command.java:90)
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:126)
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92)
For complete error details, refer to the log at /var/log/elasticsearch/elasticsearch.log
Is the problem maybe due to the ingest-attachment plugin?
EDIT: Reinstalling the ingest-attachment plugin solved the problem. https://discuss.elastic.co/t/elastic-search-crashes-after-start/169957/3