更改ulimit配置文件是不起作用的，需要修改service单元文件：

[Service]
LimitNOFILE=8192

有效的Limit选项可以运行man 5 systemd.exec查看。

  LimitCPU=, LimitFSIZE=, LimitDATA=, LimitSTACK=, LimitCORE=, LimitRSS=,
       LimitNOFILE=, LimitAS=, LimitNPROC=, LimitMEMLOCK=, LimitLOCKS=,
       LimitSIGPENDING=, LimitMSGQUEUE=, LimitNICE=, LimitRTPRIO=,
       LimitRTTIME=
           These settings control various resource limits for executed
           processes. See setrlimit(2) for details. Use the string infinity to
           configure no limit on a specific resource.

参考资料：

https://serverfault.com/questions/649577/how-can-i-permanently-set-ulimit-n-8192-in-centos-7#answer-720596

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/sect-managing_services_with_systemd-unit_files#sect-Managing_Services_with_systemd-Unit_File_Create

https://access.redhat.com/solutions/1257953