在工作中使用mysql数据库的时候或许会遇到下面这个错误：

[ERROR] when opening file: '/var/tmp/#sql_2ad6_1.MAD' (Errcode: 24)

这是因为Mariadb（MySQL）打开的文件描述符个数超出了open_files_limit的限制，这时我们需要先检查一下数据库当前open_files_limit的值：

mysql> show global variables like 'open_files_limit';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| open_files_limit | 1024  |
+------------------+-------+
1 row in set (0.00 sec)


为了解决这个问题，就需要将open_files_limit重新设置比较大一点，怎么做呢？很简单

首先我们先看一下Mariadb的设置说明：

#cat /usr/lib/systemd/system/mariadb.service

# It's not recommended to modify this file in-place, because it will be

# overwritten during package upgrades.  If you want to customize, the

# best way is to create a file "/etc/systemd/system/mariadb.service",

# containing

#       .include /lib/systemd/system/mariadb.service

#       ...make your changes here...

# or create a file "/etc/systemd/system/mariadb.service.d/foo.conf",

# which doesn't need to include ".include" call and which will be parsed

# after the file mariadb.service itself is parsed.

#

# For more info about custom unit files, see systemd.unit(5) or

# http://fedoraproject.org/wiki/Systemd#How_do_I_customize_a_unit_file.2F_add_a_custom_unit_file.3F

 

# For example, if you want to increase mariadb's open-files-limit to 10000,

# you need to increase systemd's LimitNOFILE setting, so create a file named

# "/etc/systemd/system/mariadb.service.d/limits.conf" containing:

#       [Service]

#       LimitNOFILE=10000

 

# Note: /usr/lib/... is recommended in the .include line though /lib/...

# still works.

# Don't forget to reload systemd daemon after you change unit configuration:

# root> systemctl --system daemon-reload


这样就很简单了吧。。。。。

首先创建一个目录

#mkdir -p /etc/systemd/system/mariadb.service.d/


在该目录下创建一个limits.conf，添加如下内容

[Service]
LimitNOFILE=10240

接着重新加载一下

#systemctl daemon-reload

最后重新启动一下Mariadb（mysql）服务

#systemctl restart mariadb

接着在来查看一下设置后的open_files_limit的值：

mysql> show global variables like 'open_files_limit';
+------------------+-------+
| Variable_name    | Value |
+------------------+-------+
| open_files_limit | 10240 |
+------------------+-------+
1 row in set (0.08 sec)

这样就OK了。

 

或者来一个最直接暴力的：

直接在/usr/lib/systemd/system/mariadb.service中添加LimitNOFILE=10240

如下： 

[Unit]

Description=MariaDB database server

After=syslog.target

After=network.target

 

[Service]

Type=simple

User=mysql

Group=mysql

LimitNOFILE=10240

 

接着重新加载一下

#systemctl daemon-reload

最后同样重启一下Mariadb（mysql）服务

#systemctl restart mariadb