MySQL Command Line Error Recovery

When executing multi-line statements in the MySQL command-line interface, an error in a preceding line can be frustrating. Use the \c command to cancel the current input and return to the "mysql->" prompt.

Tomcat Service Management

Navigate to the Tomcat bin directory first: cd /usr/local/tomcat/bin

• Start service: ./startup.sh
• Stop service: ./shutdown.sh

Verifying Tomcat Shutdown

Check for remaining Java processes: ps -ef|grep java

root      7010     1  0 Apr19 ?        00:30:30 [java] <defunct>

The presence of a defunct process indicates successful shutdown.

Real-time Tomcat Log Monitoring

1. Navigate to logs directory: cd tomcat/logs
2. Monitor output: tail -f catalina.out
3. Exit with Ctrl+c

Resolving Tomcat Memory Issues

For OutOfMemoryError exceptions, modify /bin/catalina.sh by adding these JVM options before the "Using CATALINA_BASE" echo statement:

JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1024m -Xmx1024m -XX:NewSize=512m -XX:MaxNewSize=256m -XX:PermSize=512m -XX:MaxPermSize=512m"

Vim Editor Essentials

Editing files: vi /usr/local/mytxt

• Enter insert mode with i
• Exit insert mode with Esc
• Save and quit: :wq followed by Enter

Linux Firewall Management

Persistent settings (survive reboot):

• Enable: chkconfig iptables on
• Disable: chkconfig iptables off

Immediate settings (reset on reboot):

• Enable: service iptables start
• Disable: service iptables stop
• Check status: service iptables status

Individual Port Configuration

1. Open port: /sbin/iptables -I INPUT -p tcp --dport 8080 -j ACCEPT
2. Save configuration: /etc/rc.d/init.d/iptables save
3. Restart service: /etc/init.d/iptables restart
4. Verify opening: /sbin/iptables -L -n

SELinux Management

Check status: /usr/sbin/sestatus -v or getenforce

Temporary disable: setenforce 0

Permanent disable: Edit /etc/selinux/config, change SELINUX=enforcing to SELINUX=disabled, then reboot.

MySQL Administration Commands

Connection: mysql -hlocalhost -uroot -p -P3306

Password modification:

mysql -uroot -p
mysql> use mysql;
mysql> update user set authentication_string=password('newpass') where user='root';
mysql> flush privileges;
mysql> exit;

Basic operations:

• show databases;
• use database_name;
• show tables;
• quit;
• create database new_db;

MySQL Case Sensitivity Configuration

Add to /etc/my.cnf under [mysqld] section:

lower_case_table_names=1

Values: 0 = case-sensitive, 1 = case-insensitive. Restart MySQL after change.

MySQL Character Encoding

Check encoding: show variables like 'character%';

Configure UTF-8 in /etc/my.cnf:

[client]
default_character_set=utf8

[mysqld]
collation_server = utf8_general_ci
character_set_server = utf8

MySQL Status Monitoring

Display runtime information: STATUS;

MySQL Backup Procedures

For automated backup strategies, see separate documentation on Linux MySQL backup automation.