我已经成功地增加了本地用户的 nofile 和 nproc 值，但是我找不到 systemd 启动的进程的合适解决方案。将 max_open_files 添加到 MariaDB 配置没有帮助。su - mysql手动更改限制也不起作用（此帐户当前不可用）。
/etc/security/limits.conf
* soft nofile 102400
* hard nofile 102400
* soft nproc 10240
* hard nproc 10240
/etc/security/limits.d/20-nproc.conf（目录中没有其他文件）
* soft nofile 102400
* hard nofile 102400
* soft nproc 10240
* hard nproc 10240
/etc/sysctl.conf
fs.file-max = 2097152
/etc/pam.d/system-auth
#%PAM-1.0
# This file is auto-generated.
# User changes will be destroyed the next time authconfig is run.
auth required pam_env.so
auth sufficient pam_unix.so nullok try_first_pass
auth requisite pam_succeed_if.so uid >= 1000 quiet_success
auth required pam_deny.so
account required pam_unix.so
account sufficient pam_localuser.so
account sufficient pam_succeed_if.so uid < 1000 quiet
account required pam_permit.so
password requisite pam_pwquality.so try_first_pass local_users_only retry=3 authtok_type=
password sufficient pam_unix.so sha512 shadow nullok try_first_pass use_authtok
password required pam_deny.so
session optional pam_keyinit.so revoke
session required pam_limits.so
-session optional pam_systemd.so
session [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session required pam_unix.so
/etc/pam.d/systemd-user
#%PAM-1.0
# Used by systemd when launching systemd user instances.
account include system-auth
session include system-auth
auth required pam_deny.so
password required pam_deny.so
/var/log/mariadb/mariadb.log
[Warning] Changed limits: max_open_files: 1024 max_connections: 32 table_cache: 491
/proc/mysql_pid/limits
Limit Soft Limit Hard Limit Units
Max cpu time unlimited unlimited seconds
Max file size unlimited unlimited bytes
Max data size unlimited unlimited bytes
Max stack size 8388608 unlimited bytes
Max core file size 0 unlimited bytes
Max resident set unlimited unlimited bytes
Max processes 30216 30216 processes
Max open files 1024 4096 files
Max locked memory 65536 65536 bytes
Max address space unlimited unlimited bytes
Max file locks unlimited unlimited locks
Max pending signals 30216 30216 signals
Max msgqueue size 819200 819200 bytes
Max nice priority 0 0
Max realtime priority 0 0
Max realtime timeout unlimited unlimited us
有趣的是，不同的进程（用户）有不同的最大打开文件数：
mysql - 1024 4096
apache - 1024 4096
postfix - 4096 4096