I did. There is no file called : /etc/security/limits.conf
There is one /usr/etc/security/limits.conf and I have already modified but did not get any success. After changing the values and restarting the machine:
./solr start
neither jattach nor jstack in /usr/lib64/jvm/jre-openjdk could be found, so no thread dumps are possible. Continuing.
*** [WARN] *** Your open file limit is currently 1024.
It should be set to 65000 to avoid operational disruption.
If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in.sh
*** [WARN] *** Your Max Processes Limit is currently 31193.
It should be set to 65000 to avoid operational disruption.
If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in.sh
ulimit -Sn
1024
ulimit -Hn
524288
echo $$
3087
systemd-cgls
This is 163 lines output, is it okay to paste it in here?
Your shell with PID 3087 does not run as part of login session. It is started by systemd user instance. The limits.conf settings apply only to the processes that are part of user session (these limits are used by pam_limits module executed during login). If you login on the console or via ssh, you will see the expected values.
It is possible to switch KDE back to traditional session management so limits.conf applies. If you do not want it, you need to apply limits to the user systemd units. It can be done globally, for all units, via global configuration file or set only for individual user instance (in your case, for user@1000.service).