what is the root zone?
The DNS translates domain names that humans can remember into the numbers used by computers to look up its destination (a little like a phone book is used to look-up a phone number). It does this in stages. The first place it ‘looks’ is the top level of the directory service - or “root zone”. So to use www.google.com as an example, your computer ‘asks’ the root zone directory (or top level) where to find information on “.com”. After it gets a response it then asks the “.com” directory service identified by the root where to find information on .google.com (the second level), and finally asking the google.com directory service identified by “.com” what the address for www.google.com is (the third level). After that process – which is almost instantaneous – the full address is provided to your computer. Different entities manage each one of these directory services: google.com by Google, “.com” by VeriSign Corporation (other top level domains are managed by other organizations), and the root zone by ICANN.
Tags: Root, zone
Initializing Physical Volumes
Use the pvcreate command to initialize a block device to be used as a physical volume.
Initialization is analogous to formatting a file system.
The following command initializes /dev/sdd, /dev/sde, and /dev/sdf as LVM physical volumes for later use as part of LVM logical volumes.
pvcreate /dev/sdd /dev/sde /dev/sdf
Tags: Initializing, l Volumes, Physica
PHP Error Handling and Logging
Display_startup_errors
Even when display_errors is on, errors that occur during PHP’s startup sequence are not displayed. It’s strongly recommended to keep display_startup_errors off, except for debugging.
These are functions dealing with error handling and logging. They allow you to define your own error handling rules, as well as modify the way the errors can be logged. This allows you to change and enhance error reporting to suit your needs.
With the logging functions, you can send messages directly to other machines, to an email (or email to pager gateway!), to system logs, etc., so you can selectively log and monitor the most important parts of your applications and websites.
The error reporting functions allow you to customize what level and kind of error feedback is given, ranging from simple notices to customized functions returned during errors.
Tags: error, Handling, Logging, PHP
ChkServd TCP check failure threshold
Main >> Server Configuration >> Tweak Settings
The number of times a ChkServd TCP check must fail before notification is sent and the service is restarted. On heavily loaded systems these types of service checks fail occasionally, producing erroneous indications that services are down.
A value of 3 or higher is recommended for most systems.
Tags: check, chkservd, failure, tcp, threshold
Linux performance tuning -vm.swappiness
Linux kernel has improved memory subsystem, with which administrators now have a simple interface to fine-tune the swapping behavior of the kernel. The linux kernel tunable parameter vm.swappiness (/proc/sys/vm/swappiness) can be used to define how aggressively memory pages are swapped to disk.
Linux moves memory pages that have not been accessed for some time to the swap space even if there is enough free memory available. By changing the percentage in /proc/sys/vm/swappiness you can control the swapping behavior, depending on the system configuration.
A high swappiness value means that the kernel will be more apt to unmap mapped pages. A low swappiness value means the opposite, the kernel will be less apt to unmap mapped pages. In other words, the higher the vm.swappiness value, the more the system will swap.
Tags: linux, Performance, tuning, vm.swappiness
