Basics There are two common options for backing up a MySQL cluster database: mysqldump or a native cluster backup. The utility mysqldump is more general since it is a storage engine independent. It has an advantage in that you can usually restore to a different table type with only minor effort. Also with it, backups can be limited to only certain databases or even tables. Since the dump file is written as SQL INSERT statements, it may take some time to restore, though. Note: It is strongly … [Read more...] about How to Backup a MySQL Cluster
How to Configure 2-way replication in an existing Master, Slave MySQL Replication environment
This post applies both to Server and Cluster environments, as cluster replication uses the MySQL Server / API node to facilitate the replication. There are minor config differences between the two databases, however, the core replication configuration is similar. The main requirement is that an existing M/S (Master/Slave) replication channel exists and is functioning nominally in the environment, which will then be extended to M/M (Master/Master). Configuring the existing replication SLAVE … [Read more...] about How to Configure 2-way replication in an existing Master, Slave MySQL Replication environment
Linux “seq” Command Examples
The seq command prints a sequence of integers or real numbers, suitable for piping to other programs. The seq command can come in handy in various other commands and loops to generate sequence of numbers. The Syntax The general syntax of the "seq" command is: # seq [options] specification The examples 1. To simply print a sequence of number starting from a 1, use the below command: # seq 4 1 2 3 4 By default, seq command starts printing the sequence of numbers from 1, if not … [Read more...] about Linux “seq” Command Examples
How to Install an Configure MASTER PDF EDITOR IN UBUNTU
Introduction In this article we are going to learn How to install master PDF editor in Ubuntu 16.04. master PDF editor is a open source free PDF editor application for Linux. It’s a light weight and user friendly application to use. This application is not only a PDF editor but more than that, you can use this application for completely free but for more features you can purchase its pro version. Now let’s have a look at features of master PDF editor: It’s an cross platform application … [Read more...] about How to Install an Configure MASTER PDF EDITOR IN UBUNTU
How to check and repair ACFS with FSCK
The Problem You noticed many inconsistencies in different asm metadata views, asmcmd and os outputs that are associated with the ACFS file system. Database shows corruption in RMAN or from dbverify. Database uses ACFS. ALTER DISKGROUP CHECK REPAIR comes back clean but you still see errors or check for corruption returns back positive, eg: $ /sbin/acfsutil info fs -o iscorrupt [MOUNT_POINT] acfsutil info fs: ACFS-03037: not an ACFS file system $ /sbin/acfsutil info fs -o iscorrupt … [Read more...] about How to check and repair ACFS with FSCK
How to test a PHP script
PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. PHP runs on all major operating systems, from Unix variants including Linux, FreeBSD, Ubuntu, Debian, and Solaris to Windows and Mac OS X. It can be used with all leading web servers, including Apache, Nginx, OpenBSD servers to name a few; even cloud environments like Azure and Amazon are on the rise. Below are some of the ways in which a PHP script can be … [Read more...] about How to test a PHP script
How to Set Space limits for MySQL for database/schema/table
MySQL itself has not such quotas, but it is possible to partially manage quota limitation at engine level. For MyISAM it is possible to limit table size using option myisam_data_pointer_size This variable limits default data pointer size: less this variable is, less rows would be allowed to be saved in the table. "Table is full" error will be reported if this option is considered. For InnoDB it is possible to specify hard limit of shared tablespace: syntax is similar to … [Read more...] about How to Set Space limits for MySQL for database/schema/table
How to Configure SSH to restrict Users/Groups with allow and deny directives
Question: How can we restrict user/group access to a system using ssh? SSH uses specific files for configuration to achieve these various restrictions. Inbound ssh sessions (into the host) are handled by sshd (the ssh daemon). This process has its own configuration file, /etc/ssh/sshd_config. The parameters in the /etc/ssh/sshd_config file that apply are AllowGroups, AllowUsers, DenyGroups, and DenyUsers. If these parameters are set, it will affect all users from all hosts. To restrict … [Read more...] about How to Configure SSH to restrict Users/Groups with allow and deny directives
How to allow ssh with empty passwords in Linux
Question: How can we allow a user with empty password to login to a Linux system? Although it seems a risky requirement, but sometimes in a private, development environment this can come handy. Also openssh provides you with an option to have empty passwords for users while doing ssh. From the man page of sshd_config: # man sshd_config ... PermitEmptyPasswords When password authentication is allowed, it specifies whether the server allows login to accounts with empty … [Read more...] about How to allow ssh with empty passwords in Linux
What is the difference between & (ampersand) and && (double ampersand) while executing simultaneous commands on Linux
To run more that one command simultaneously we can use the & (ampersand) special character. Another use of & is running the commands in the background. In that case though, you should use & once and the end of the command or script. For example: # [some command or script] & Using & (ampersand) to run commands simultaneously In order to run 2 commands simultaneously use the & special character between the 2 or more commands. The syntax is: # command1 & command2 & command3 .. For example, … [Read more...] about What is the difference between & (ampersand) and && (double ampersand) while executing simultaneous commands on Linux