RHEL6 - 31 - RPM

RHEL6-31-RPM

Red Hat has simplified the installation of software in Linux by creating the Red Hat Package Manager (RPM). A package, or RPM file, will install a given application and create the necessary directories to run it.

An RPM package can contain an arbitrary set of files. The larger part of RPM files encountered are “binary RPMs” (or BRPMs) containing the compiled version of some software. There are also “source RPMs” (or SRPMs) files containing the source code used to produce a package. These have an appropriate tag in the file header that distinguishes them from normal (B)RPMs, causing them to be extracted to /usr/src on installation. SRPMs customarily carry the file extension “.src.rpm” (.spm on file systems limited to 3 extension characters, e.g. old DOS FAT).

RHEL6 - 30 - CHROOT JAIL (FTP/SFTP)

RHEL6-30-CHROOT JAIL (FTP/SFTP)

WHAT IS CHROOT-JAIL?

A chroot operation changes the apparent root directory for a running process and its children. It allows you to run a program with a root directory other than /. The program cannot see or access files outside the designated directory tree. Such an artificial root directory is called a chroot jail, and its purpose is to limit the directory access of a potential attacker. The chroot jail locks down a given process and any user ID that it is using so that all they see is the directory in which the process is running. To the process, it appears that the directory in which it is running is the root directory. 

RHEL6 - 29 - TCP WRAPPERS

RHEL6-29-TCP WRAPPERS

  

WHAT IS TCP WRAPPER?

As name suggest, wrapping of TCP, protection of services that communicate using the TCP protocol.

The Linux services or commands that can be controlled through tcp_wrappers are those that use the libwrap library.

For network services that utilize it, TCP Wrappers add an additional layer of protection by defining which hosts are or are not allowed to connect to "wrapped" network services. One such wrapped network service is the xinetd super server. This service is called a super server because it controls connections to a subset of network services and further refines access control.

RHEL6 - 28 - XINETD

RHEL6-28-XINETD

xinetd stands for “extended internet service daemon”

To control access to Internet services, use xinetd, which is a secure replacement for inetd. The xinetd daemon conserves system resources, provides access control and logging, and can be used to start special-purpose servers. xinetd can also be used to grant or deny access to particular hosts, provide service access at specific times, limit the rate of incoming connections, limit the load created by connections, and more.

RHEL6 – 27 - SSH

RHEL6–27-SSH

  

SSH:

SSH is a client/server protocol, which helps us to access the remote system over the network. The communication done via encrypted tunnel. Whenever client access the server, the client downloads the secure key from server and simultaneously server fetch the secure key from client. These keys make the secure encrypted tunnel between client/server for communication.

RHEL6 - 26 - TELNET

RHEL6-26-TELNET

HOW TO CONFIGURE TELNET IN RHEL6?

Telnet is very unsecure way to connect with other system. This is unsecure because communication between systems is in plain text.

By default

-   Telnet is not installed,

-   User “root” is not allowed,

-   After installing telnet again telnet login is not permitted.

RHEL6 - 25 - VIRTUAL IP

RHEL6-25-VIRTUAL IP

HOW TO CONFIGURE VIRTUAL IP IN RHEL6?

Before configuring virtual IP we need to know how many network interfaces are available?

Various ways to find available Network Interfaces on the RHEL system.

RHEL6 - 24- LINUX KERNEL - 3

RHEL6-24-LINUX KERNEL -3

KERNEL TUNING:

Kernel Tuning via /proc/sys          Temporary

Kernel Tuning via sysctl             Temporary

Kernel Tuning via /etc/sysctl.conf   Permanent

Kernel Tuning via /proc/proc                Temporary

RHEL6-23-LINUX KERNEL -2

RHEL6-23-LINUX KERNEL -2

KERNEL TUNING:

As we already know that “lsmod” is used to get the info about loaded modules.

LOADING KERNEL MODULES:

There are 2 ways to load the kernel modules, “insmod” and “modprobe”

“insmod” inserts a single module into the kernel, provided underlying dependencies are already loaded.

RHEL6-22-LINUX KERNEL -1

RHEL6-22-LINUX KERNEL -1

THE LINUX KERNEL:

The kernel is the central module of an operating system (OS). It is the part of the operating system that loads first, and it remains in main memory. Because it stays in memory, it is important for the kernel to be as small as possible while still providing all the essential services required by other parts of the operating system and applications. The kernel code is usually loaded into a protected area of memory to prevent it from being overwritten by programs or other parts of the operating system.

Typically, the kernel is responsible for memory management, process and task management, and disk management. The kernel connects the system hardware to the application software. Every operating system has a kernel. For example the Linux kernel is used numerous operating systems including Linux, FreeBSD, Android and others.

RHEL6-21-LOGICAL VOLUME MANAGER (LVM)-8

RHEL6-21-LOGICAL VOLUME MANAGER (LVM)-8

LVM OPERATIONS:

VOLUME RE-LAYOUT:

How to know the volume layout (Linear, Mirrored and striped) of existing LV’s?

How to change a linear volume to mirrored volume in LVM?

How to change a stripe volume to linear volume in LVM?

How to change a mirror volume to linear volume in LVM?

How to change a linear volume to stripe volume in LVM?

RHEL6-20-LOGICAL VOLUME MANAGER (LVM)-7

RHEL6-20-LOGICAL VOLUME MANAGER (LVM)-7

LVM OPERATIONS:

IMPORT & DEPORT OF VOLUME GROUP (VG):

LVM CONFIGURATION BACKUP & RESTORE:

How to do vgexport in linux?

How to do vgimport in linux?

How to move a volume group to another server in linux?

How to take backup of volume group (VG)?

What is LVM metadata?

How to restore volume group (VG)?

How to restore Logical volume group (LV) from VG backup?

Discuss various scenarios with volume group restore.

RHEL6-19-LOGICAL VOLUME MANAGER (LVM)-6

RHEL6-19-LOGICAL VOLUME MANAGER (LVM)-6

LVM OPERATIONS:

How to deactivate a VG?

How to activate a VG?

How to deactivate a LV?

How to activate a LV?

How to deactivate/activate a VG in cluster?

How to change the read/write permission of LV?

How to force a LV mirror for resync?

RHEL6-18-LOGICAL VOLUME MANAGER (LVM)-5

RHEL6-18-LOGICAL VOLUME MANAGER (LVM)-5

LVM OPERATIONS:

How to remove logical volume (LV)?

How to remove volume group (VG)?

How to remove physical volume (PV)?

How to free the disk by moving data to another disk in LVM?

How to remove the free/unused disk in LVM?

RHEL6-17-LOGICAL VOLUME MANAGER (LVM)-4

RHEL6-17-LOGICAL VOLUME MANAGER (LVM)-4

LVM OPERATIONS:

How to resize the logical volume with “lvresize”…?

How to rename the volume group (vgrename)…?

How to rename the logical volume (lvrename)…?

How to make the changes effective after vgrename and lvrename…?