ServerBuddies Support Blog

Getting List of Product Components from Parallels Plesk Panel

To get a list of the release components, issue the command of the following format:

For Parallels Plesk Panel 10.0 on a Linux/Unix server:

A list of components is displayed with component names in the left part, and indication of whether this component can be installed ([install]) or upgraded ([upgrade]), with brief descriptions in the right part, for example (fragment):

* base [install] - Parallels Plesk Panel base packages
* autoinstaller [install] - Parallels Installer
* postfix [upgrade] - Postfix mail server

The actual components are marked by [up2date].

Reference : http://parallels.com/

Firewalls the core components of a network security implementation

Firewalls can be standalone hardware solutions, such as firewall appliances by Cisco, Nokia, and Sonicwall.
There are also proprietary software firewall solutions developed for home and business markets by vendors such as Checkpoint, McAfee, and Symantec.

Firewalls function:

NAT

Network Address Translation (NAT) places private IP subnetworks behind one or a small pool of public IP addresses, masquerading all requests to one source rather than several.

Packet Filter [iptables]

A packet filtering firewall reads each data packet that passes within and outside of a LAN. It can read and process packets by header information and filters the packet based on sets of programmable rules implemented by the firewall administrator.

The Linux kernel has built-in packet filtering functionality through the Netfilter kernel subsystem.

Proxy

A proxy machine acts as a buffer between malicious remote users and the internal network client machines.

Netfilter and iptables

The Linux kernel features a powerful networking subsystem called Netfilter. The Netfilter subsystem provides stateful or stateless packet filtering as well as NAT and IP masquerading services. Netfilter also has the ability to mangle IP header information for advanced routing and connection state management. Netfilter is controlled through the iptables utility.

Examples:

iptables - administration tools for packet filtering and NAT
shorewall - Shoreline Firewall, netfilter configurator - transitional package

More about LVM Components Physical Volumes

Physical Volumes

The underlying physical storage unit of an LVM logical volume is a block device such as a partition or whole disk. To use the device for an LVM logical volume the device must be initialized as a physical volume (PV).

Initializing a block device as a physical volume places a label near the start of the device.

By default, the LVM label is placed in the second 512-byte sector. You can overwrite this default by placing the label on any of the first 4 sectors. This allows LVM volumes to co-exist with other users of these sectors, if necessary.

An LVM label provides correct identification and device ordering for a physical device, since devices can come up in any order when the system is booted. An LVM label remains persistent across reboots and throughout a cluster.

The LVM label identifies the device as an LVM physical volume. It contains a random unique identifier (the UUID) for the physical volume. It also stores the size of the block device in bytes, and it records where the LVM metadata will be stored on the device.

The LVM metadata contains the configuration details of the LVM volume groups on your system. By default, an identical copy of the metadata is maintained in every metadata area in every physical volume within the volume group. LVM metadata is small and stored as ASCII.