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Getting Error - Could not open file '/mysql/<db_name>/logs/<db_name>.err' for error logging: Permission denied: If you are implementing systemctl to start, stop, and check status of mysqld and getting following error, while starting mysqld service, then check whether SeLinux is disabled or not. mysqld[44278]: 2018-11-06T01:36:48.303642Z 0 [ERROR] [MY-010187] [Server] Could not open file '/mysql/<db_name>/logs/<db_name>.err' for error logging: Permission denied mysqld[44278]: 2018-11-06T01:36:48.303785Z 0 [ERROR] [MY-010119] [Server] Aborting Disable SeLinux: Check whether SeLinux is enforcing or permissive # getenforce Enforcing Edit file /etc/sysconfig/selinux and set SELINUX=permissive as follows and REBOOT server # cat /etc/sysconfig/selinux # This file controls the state of SELinux on the system. # SELINUX= can take one of these three values: #     enforcing - SELinux security policy is enforced. #     permissive - SELinux prints warnings in

Can't change size of file (OS errno 28 - No space left on device): You might surprise even though there is plenty of free space available on the disk and you encounter " Can't change size of file (OS errno 28 - No space left on device): " while using MySQL database server. There could be multiple reason for it. I have implemented different fix for different environment, such as Increase physical memory and inndo_buufer_pool_size Increase tmp_table_size Increase max_heap_table_size BUT In one of the environment issue was fixed only after setting innodb_temp_data_file_path = /mysql/<db_name>/temp/ibtmp1:1G:autoextend

ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema'": If you are getting following error when trying to grant select privilege on infomation_schema, then explore what is information_schema and you don't need to grant select to any user for information_schema. ERROR 1044 (42000): Access denied for user 'root'@'localhost' to database 'information_schema' Information_schema database for mysql is specialized, virtual database. By default all users have select privilege on database information_schema. Even root user can't insert, update, delete, and drop objects of information_schema database. Information_schema database, built when service is started. Explore more about information_schema at https://dev.mysql.com/doc/refman/8.0/en/information-schema-introduction.html

Install MySQL agent unattended mode / non-interactive mode: 01. Get file mysqlmonitoragent-8.0.3.8197-linux-x86-64bit-installer.bin from Oracle e-delivery. 02. Copy file mysqlmonitoragent-8.0.3.8197-linux-x86-64bit-installer.bin to /tmp/ of the target server where agent need to install. 03. Create options file - options.txt and include following parameters. debuglevel=4 installer-language=en debugtrace=/mysql/MEM803/agent/install.debugtrace.monitor.log mode=unattended # User defined installation location of agent installdir=/mysql/MEM803/agent/ # Following is the server where MySQL Service Manager is running managerhost=<MEM Server> managerport=<Port No. of MEM server> # Following is the user created on MEM and not in MySQL database agentuser=msqlagent agentpassword=<code> # database type of installation will monitor server and database agent_installtype=database # Mysql user of the server where agent is installed mysqluser=root mysqlpassword=<code> # Mysql serv

Can't start mysqld using systemctl:  | Permission Denied 01. Check SELinux is enforced or not using following command, if the value is enforced means SELinux is enforced. #getenforce 02. Edit file /etc/selinux/config and set SELINUX=permissive 03. Reboot server, and type following command to see value permissive. #getenforce 05. Check status using following command #sestatus 04. Execute following command to start mysqld #sysetmctl start mysqld Explore more how to disable SELinux at following link https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/security-enhanced_linux/sect-security-enhanced_linux-working_with_selinux-changing_selinux_modes