Linux Ocean

Setting up sudo users in Linux

2012-05-24T00:28:00.001-07:00

This video explains about setting up sudo users in Linux.

Course Outline for Ubuntu 12.04

2012-05-23T04:36:00.001-07:00

Course methodology

This course helps transition participants from graphical user interface tools to the command-line interface. It provides a solid background in Linux using Ubuntu as the environment for exploration and learning. Lab exercises combined with highly engaging activities will be used to reinforce learning objectives.

Course schedule

Days 1 + 2: General Linux and Ubuntu introduction

Lesson 1: Ubuntu background and Linux (1 hour)

Describe the history of Linux and the Ubuntu distribution.
Explain the Ubuntu release cycle.
Describe the Ubuntu community structure and governance board.

Lesson 2: Ubuntu desktop tour (1 hour)

Describe the key features of Ubuntu Desktop.
Customise the desktop settings.
Navigate to directories and files in Nautilus.
Install and remove applications.
Add new language settings.

Lesson 3: Using the command line interface (CLI) and sudo (3 hours)

Essential CLI commands.
- cd, ls, grep, echo, uname, cat, less, more, rm, mkdir, touch, mv, nano.
- arguments.
- man command.
- sudo command.

Lesson 4: Networking basics (2 hours)

Current configuration of network interfaces.
- ip, ipconfig, /etc/resolv.conf, route.
Changing the network configuration.
Testing for a working network connection.
- ping, dig, host, nslookup.
• Managing the network with Network Manager.
- adsl, wifi, ethernet.
Analyzing the network using Network Tools.

Lesson 5: Filesystem and basic backups (3 hours)

Storage device naming system.
The Filesystem Hierarchy Standard (FHS).
Mounting and unmounting devices.
- mount, umount.
Configuring fstab.
- /etc/fstab.
Symbolic links.
Creating an ext4 file system.
- ext2, ext4, xfs, mkfs.
Managing file systems.
- fsck, debugfs, dump2fs, e2label.

Lesson 6: Permissions - User management (4 hours)

Managing user accounts and groups.
- adduser, deluser, addgourp, delgroup.
Different file system permissions.
Assigning permissions to different users and groups.
- chmod, chown, chgrp.
Creating default settings for new user accounts.
- /etc/adduser.conf.
Creating a default environment using /etc/profile.

Lesson 7: Process management (2 hours)

Displaying and interpreting process statistics.
- top, ps.
Managing processes.
- kill, nice, renice.
Scheduling processes (pending upstart plans).
- at, cron.
Finding out who's using files or devices.
- lsof

Days 3 - 5

Lesson 8: Ubuntu background, community and support (2 hours)

The Ubuntu community structure and governance board.
Technical board, Linus, Linux, GNU, Debian.
Support resources from Canonical, partners, and the user community including:
Mailing lists.
IRC channels.
Launchpad and other sources for researching and reporting bugs.
Official Ubuntu documentation and community documentation.
Ubuntu release cycle.
LTS, regular.

Lesson 9: Service management (6 hours)

Upstart.
SystemV compatibility.
Starting and stopping system services.
Kernel management and boot procedures (2 hours)
Explain the working and functionality of Grub2.
- update-grub[2].
Customise the Grub2 boot environment.
- /etc/default/grub.
Explain the modular kernel.
- modinfo, /etc/modules, /lib/modules, /boot, /etc/initramfs, update- initramfs.
Manage kernel modules.
- modprobe, rmmod, /etc/modprobe.d.
Describe how udev creates device interfaces for hardware.
- udev rules, udevadm, /etc/udev/rules.d.
Hardware management and monitoring (2 hours)
Manage partitions.
- fdisk, cfdisk, system->administration->disk utility, parted.
Display hardware information.
- lsusb, lshw, lspci, dmesg, lscpu, lsscsi.
Monitor a hard drive through the SMART interface.
- smartctl.
Use the memtest facility.
- /boot/memtest86+.bin, grub.

Lesson 10 - Package management (3 hours)

Explain how packages are used in Ubuntu.
- packages vs applications, dependencies, conflicts, recommendations.
Explain apt system, repositories and meta packages.
- apt-get, apt-cache, apt-key, repositories, meta packages.
Manage packages using the appropriate tools.
- tasksel, update-manager, Ubuntu Software Centre.

Lesson 11 - Providing services (3 hours)

Setup a basic LAMP environment.
- tasksel install lamp-server.
- /var/www/phpinfo.php.
Setup a basic Samba file server.
- apt-get install samba.
- /etc/samba.smb.conf..
- smbpasswd.
Set up SSH for remote access.
- apt-get install ssh.

Lesson 12 - Security (2 hours)

Explain how AppArmor uses default profiles to secure your services.
- /etc/apparmor.d.
Display current profiles used by AppArmor.
- aa-status.
Explain how UFW works to protect your system.
- ufw.
Configure UFW.
- ufw enable|disable etc.

Lesson – 13 GNOME configuration (2 hours)

Localise your GNOME environment.
- system -> administration -> language support.
Manage your GNOME configuration and restore a default state.
- gconf-editor, gconftool.
Customise the GNOME environment.
- gdmsetup, /etc/gdm/.
Connect to a network printer.
- system -> administration -> printing.

Lesson 14 - Monitoring / Landscape (1 hour)

Set up munin for monitoring.
- apt-get install munin munin-node, /etc/munin/.
Set up a landscape account.
- apt-get install landscape-client ; dpkg-reconfigure landscape-client.
Register a computer with landscape.

DNS works good in Red Hat Enterprise Linux 6

2012-01-30T04:10:00.000-08:00

This video explains about the basic DNS configuration in Red Hat Enterprise Linux 6.

YUM Server Configuration in RHEL 6 (Yellow Dog Updater Modified) FTP Method

2012-01-21T03:40:00.000-08:00

Server side configuration:

Step 1:

Install createrepo.rpm from the DVD for creating repository.

#rpm -ivh createrepo.rpm (Install the dependencies first, if any [eg:deltarpm, python-deltarpm])

#rpm -ivh vsftpd.rpm (for FTP server)

Step 2:

Copy all rpms form the DVD and past over the hard disk share them up in NFS.

#createrepo /path-to-rpms

eg:#createrepo /var/ftp/pub

It will take several minutes that depends upon the number of rpms that you have copied from the DVD specified and the configuration of yourmachine.

Step 3:

#service vsftpd restart

Touch the following file with the contents specified.

#vim /etc/yum.repos.d/somename.repo

[base]

name=friendly name

baseurl=ftp://192.168.0.254/pub/ (Give the ipaddress of the YUM server)

enabled=1

gpgcheck=0

Step 4:

Use the yum server in the same machine because server is the first client of the same service most of the times the following command is used for install gcc compiler

#yum install gcc

Client side configuration:

Touch the following file with the contents specified.

#vim /etc/yum.repos.d/somename.repo

[base]

name=friendly name

baseurl=ftp://192.168.0.254/pub/ (Give the ipaddress of the YUM server)

enabled=1

gpgcheck=0

#yum install gcc (just for an example)

Mounting an iso file in Linux (Fedora, Redhat)

2012-01-20T03:07:00.000-08:00

#mkdir /rhel6 (creating a mount point – an empty directory)

#mount –t iso9660 –o loop rhel6.iso /rhel6 (actual mounting is taken place)

#cd /rhel6 (change to the directory)

#ls (listing down the iso content)

Nameserver Types

2011-09-19T05:03:00.001-07:00

There are two nameserver configuration types:

authoritative: Authoritative nameservers answer to resource records that are part of their zones only. This category includes both primary (master) and secondary (slave) nameservers.
recursive: Recursive nameservers offer resolution services, but they are not authoritative for any zone. Answers for all resolutions are cached in a memory for a fixed period of time, which is specified by the retrieved resource record.

Although a nameserver can be both authoritative and recursive at the same time, it is recommended not to combine the configuration types. To be able to perform their work, authoritative servers should be available to all clients all the time. On the other hand, since the recursive lookup takes far more time than authoritative responses, recursive servers should be available to a restricted number of clients only, otherwise they are prone to distributed denial of service (DDoS) attacks.

EXT4 features

2011-09-07T02:13:00.000-07:00

1. Compatibility

Any existing Ext3 filesystem can be migrated to Ext4 with an easy procedure which consists in running a couple of commands in read-only mode (described in the next section). This means that you can improve the performance, storage limits and features of your current filesystems without reformatting and/or reinstalling your OS and software environment. If you need the advantages of Ext4 on a production system, you can upgrade the filesystem. The procedure is safe and doesn't risk your data (obviously, backup of critical data is recommended, even if you aren't updating your filesystem :). Ext4 will use the new data structures only on new data, the old structures will remain untouched and it will be possible to read/modify them when needed. This means, that, of course, that once you convert your filesystem to Ext4 you won't be able to go back to Ext3 again (although there's a possibility, described in the next section, of mounting a Ext3 filesystem with Ext4 without using the new disk format and you'll be able to mount it with Ext3 again, but you lose many of the advantages of Ext4).

2. Bigger filesystem/file sizes

Currently, Ext3 support 16 TB of maximum filesystem size, and 2 TB of maximum file size. Ext4 adds 48-bit block addressing, so it will have 1 EB of maximum filesystem size and 16 TB of maximum file size. 1 EB = 1,048,576 TB (1 EB = 1024 PB, 1 PB = 1024 TB, 1 TB = 1024 GB). Why 48-bit and not 64-bit? There are some limitations that would need to be fixed before making Ext4 fully 64-bit capable, which have not been addressed in Ext4. The Ext4 data structures have been designed keeping this in mind, so a future update to Ext4 will implement full 64-bit support at some point. 1 EB will be enough (really :)) until that happens. (Note: The code to create filesystems bigger than 16 TB is -at the time of writing this article- not in any stable release of e2fsprogs. It will be in future releases.)

3. Sub directory scalability

Right now the maximum possible number of sub directories contained in a single directory in Ext3 is 32000. Ext4 breaks that limit and allows a unlimited number of sub directories.

4. Extents

The traditionally Unix-derived filesystems like Ext3 use a indirect block mapping scheme to keep track of each block used for the blocks corresponding to the data of a file. This is inefficient for large files, specially on large file delete and truncate operations, because the mapping keeps a entry for every single block, and big files have many blocks -> huge mappings, slow to handle. Modern filesystems use a different approach called "extents". An extent is basically a bunch of contiguous physical blocks. It basically says "The data is in the next n blocks". For example, a 100 MB file can be allocated into a single extent of that size, instead of needing to create the indirect mapping for 25600 blocks (4 KB per block). Huge files are split in several extents. Extents improve the performance and also help to reduce the fragmentation, since an extent encourages continuous layouts on the disk.

5. Multiblock allocation

When Ext3 needs to write new data to the disk, there's a block allocator that decides which free blocks will be used to write the data. But the Ext3 block allocator only allocates one block (4KB) at a time. That means that if the system needs to write the 100 MB data mentioned in the previous point, it will need to call the block allocator 25600 times (and it was just 100 MB!). Not only this is inefficient, it doesn't allow the block allocator to optimize the allocation policy because it doesn't knows how many total data is being allocated, it only knows about a single block. Ext4 uses a "multiblock allocator" (mballoc) which allocates many blocks in a single call, instead of a single block per call, avoiding a lot of overhead. This improves the performance, and it's particularly useful with delayed allocation and extents. This feature doesn't affect the disk format. Also, note that the Ext4 block/inode allocator has other improvements, described in detail in this paper.

6. Delayed allocation

Delayed allocation is a performance feature (it doesn't change the disk format) found in a few modern filesystems such as XFS, ZFS, btrfs or Reiser 4, and it consists in delaying the allocation of blocks as much as possible, contrary to what traditionally filesystems (such as Ext3, reiser3, etc) do: allocate the blocks as soon as possible. For example, if a process write()s, the filesystem code will allocate immediately the blocks where the data will be placed - even if the data is not being written right now to the disk and it's going to be kept in the cache for some time. This approach has disadvantages. For example when a process is writing continually to a file that grows, successive write()s allocate blocks for the data, but they don't know if the file will keep growing. Delayed allocation, on the other hand, does not allocate the blocks immediately when the process write()s, rather, it delays the allocation of the blocks while the file is kept in cache, until it is really going to be written to the disk. This gives the block allocator the opportunity to optimize the allocation in situations where the old system couldn't. Delayed allocation plays very nicely with the two previous features mentioned, extents and multiblock allocation, because in many workloads when the file is written finally to the disk it will be allocated in extents whose block allocation is done with the mballoc allocator. The performance is much better, and the fragmentation is much improved in some workloads.

7. Fast fsck

Fsck is a very slow operation, especially the first step: checking all the inodes in the file system. In Ext4, at the end of each group's inode table will be stored a list of unused inodes (with a checksum, for safety), so fsck will not check those inodes. The result is that total fsck time improves from 2 to 20 times, depending on the number of used inodes (http://kerneltrap.org/Linux/Improving_fsck_Speeds_in_Ext4). It must be noticed that it's fsck, and not Ext4, who will build the list of unused inodes. This means that you must run fsck to get the list of unused inodes built, and only the next fsck run will be faster (you need to pass a fsck in order to convert a Ext3 filesystem to Ext4 anyway). There's also a feature that takes part in this fsck speed up - "flexible block groups" - that also speeds up filesystem operations.

8. Journal checksumming

The journal is the most used part of the disk, making the blocks that form part of it more prone to hardware failure. And recovering from a corrupted journal can lead to massive corruption. Ext4 checksums the journal data to know if the journal blocks are failing or corrupted. But journal checksumming has a bonus: it allows one to convert the two-phase commit system of Ext3's journaling to a single phase, speeding the filesystem operation up to 20% in some cases - so reliability and performance are improved at the same time. (Note: the part of the feature that improves the performance, the asynchronous logging, is turned off by default for now, and will be enabled in future releases, when its reliability improves)

9. "No Journaling" mode

Journaling ensures the integrity of the filesystem by keeping a log of the ongoing disk changes. However, it is know to have a small overhead. Some people with special requirements and workloads can run without a journal and its integrity advantages. In Ext4 the journaling feature can be disabled, which provides a small performance improvement.

10. Online defragmentation

(This feature is being developed and will be included in future releases). While delayed allocation, extents and multiblock allocation help to reduce the fragmentation, with usage filesystems can still fragment. For example: You write three files in a directory and continually on the disk. Some day you need to update the file of the middle, but the updated file has grown a bit, so there's not enough room for it. You have no option but fragment the excess of data to another place of the disk, which will cause a seek, or allocate the updated file continually in another place, far from the other two files, resulting in seeks if an application needs to read all the files on a directory (say, a file manager doing thumbnails on a directory full of images). Besides, the filesystem can only care about certain types of fragmentation, it can't know, for example, that it must keep all the boot-related files contiguous, because it doesn't know which files are boot-related. To solve this issue, Ext4 will support online fragmentation, and there's a e4defrag tool which can defragment individual files or the whole filesystem.

11. Inode-related features

Larger inodes, nanosecond timestamps, fast extended attributes, inodes reservation...

* Larger inodes: Ext3 supports configurable inode sizes (via the -I mkfs parameter), but the default inode size is 128 bytes. Ext4 will default to 256 bytes. This is needed to accommodate some extra fields (like nanosecond timestamps or inode versioning), and the remaining space of the inode will be used to store extend attributes that are small enough to fit it that space. This will make the access to those attributes much faster, and improves the performance of applications that use extend attributes by a factor of 3-7 times.

* Inode reservation consists in reserving several inodes when a directory is created, expecting that they will be used in the future. This improves the performance, because when new files are created in that directory they'll be able to use the reserved inodes. File creation and deletion is hence more efficient.

* Nanoseconds timestamps means that inode fields like "modified time" will be able to use nanosecond resolution instead of the second resolution of Ext3.

12. Persistent preallocation

This feature, available in Ext3 in the latest kernel versions, and emulated by glibc in the filesystems that don't support it, allows applications to preallocate disk space: Applications tell the filesystem to preallocate the space, and the filesystem preallocates the necessary blocks and data structures, but there's no data on it until the application really needs to write the data in the future. This is what P2P applications do in their own when they "preallocate" the necessary space for a download that will last hours or days, but implemented much more efficiently by the filesystem and with a generic API. This have several uses: first, to avoid applications (like P2P apps) doing it themselves inefficiently by filling a file with zeros. Second, to improve fragmentation, since the blocks will be allocated at one time, as contiguously as possible. Third, to ensure that applications has always the space they know they will need, which is important for RT-ish applications, since without preallocation the filesystem could get full in the middle of an important operation. The feature is available via the libc posix_fallocate() interface.

13. Barriers on by default

This is an option that improves the integrity of the filesystem at the cost of some performance (you can disable it with "mount -o barrier=0", recommended trying it if you're benchmarking). From this LWN article: "The filesystem code must, before writing the [journaling] commit record, be absolutely sure that all of the transaction's information has made it to the journal. Just doing the writes in the proper order is insufficient; contemporary drives maintain large internal caches and will reorder operations for better performance. So the filesystem must explicitly instruct the disk to get all of the journal data onto the media before writing the commit record; if the commit record gets written first, the journal may be corrupted. The kernel's block I/O subsystem makes this capability available through the use of barriers; in essence, a barrier forbids the writing of any blocks after the barrier until all blocks written before the barrier are committed to the media. By using barriers, filesystems can make sure that their on-disk structures remain consistent at all times."

New in Red Hat Enterprise Linux 6

2011-07-21T22:13:00.000-07:00

Your productivity, security and flexibility are enhanced with

OpenOffice 3 suite
Email - (openchange MAPI client capability)
NetworkManager - mobile network connection management
Cisco IPSEC client compatibility
Smart Card support
Encrypted disk (luks)

High Availability Add-On

2011-07-21T22:11:00.000-07:00

High Availability Add-On

The High Availability Add-On for Red Hat Enterprise Linux provides continuous availability of services by eliminating single points of failure. By offering failover services between nodes within a cluster, the High Availability Add-On supports high availability for up to 16 nodes. (Currently this capability is limited to a single LAN or datacenter located within one physical site.)

The High Availability Add-On also enables failover for off-the-shelf applications such as Apache, MySQL, and PostgreSQL, any of which can be coupled with resources like IP address and single-node file systems to form highly available services. The High Availability Add-On can also be easily extended to any user-specified application that is controlled by an init script per UNIX System V (SysV) standards.

When using the High Availability Add-On, a highly available service can fail over from one node to another with no apparent interruption to cluster clients. The High Availability Add-On also ensures absolute data integrity when one cluster node takes over control of a service from another cluster node. It achieves this by promptly evicting nodes from the cluster that are deemed to be faulty using a method called "fencing" that prevents data corruption. The High Availability Add-On supports several types of fencing, including both power- and storage area network (SAN)-based fencing.

High Availability Add-On Features and Benefits

Features	Benefits
Clustering	Red Hat's High Availability Add-On enables applications to be highly available by reducing downtime and ensuring that there is no single point of failure in a cluster. It also isolates unresponsive applications and nodes so they can't corrupt critical enterprise data
Conga	The Conga application of Red Hat Enterprise Linux provides centralized configuration and management for the High Availability Add-On
Corosync	Corosync is a cluster executive within the High Availability Add-On that implements the Totem Single Ring Ordering and Membership Protocol, delivering an extremely mature, secure, high-performing, and lightweight high-availability solution
Integrated virtualization	Virtualization is pervasive throughout today's enterprise datacenters. Not only is Red Hat Enterprise Linux designed to be a superior guest on any of the major hypervisors, but it can also be a virtualization host. Virtualization is integrated directly into the Red Hat Enterprise Linux kernel using kernel-based virtual machine (KVM) technology. As part of the kernel, your administrators get the complete breadth of Red Hat Enterprise Linux system management and security tools and certifications
Fencing & unfencing	Fencing is removing access to resources from a cluster node that has lost contact with the cluster, thereby protecting resources such as shared storage from uncoordinated modification. Red Hat has made extensive improvements in the SCSI-3 PR reservations-based fencing. By enabling manual specification of keys and devices for registration and reservation, cluster administrators can bypass clvm and improve configuration and system flexibility. After fencing, the unconnected cluster node would ordinarily need to be rebooted to safely rejoin the cluster. However, unfencing allows a node to re-enable access when starting up without administrative intervention.
Improved cluster configuration system	The cluster configuration system now supports load options other than XML, including the Lightweight Directory Access Protocol (LDAP). Configuration reload is validated and easily synchronized across the cluster for better usability and manageability.
Virtualization integration	You can now run virtualized KVM guests as managed services
Rich graphical user interface (GUI)-based cluster management and administration	In Red Hat Enterprise Linux 6, the Web interface to luci has been redesigned and runs on TurboGears2
Unified logging and debugging	System administrators can now enable, capture, and read cluster system logs via a single cluster configuration command

courtesy: Redhat.com

Stable. Secure. Scalable. And, Innovative! Redhat Enterprise Linux 6.1 released

2011-05-20T07:23:00.000-07:00

On May 19th, Red Hat released the first service pack since the release of Red Hat Enterprise Linux 6. As with every service pack, Red Hat Enterprise Linux 6.1 consolidates all patches and security updates since the introduction of Red Hat Enterprise Linux 6, while maintaining application compatibility, ISV and IHV support.

The established performance leader as both a virtual machine guest and hypervisor host, we already set another new SpecVirt record in multi-core scaling with RHEL6.1 due to lower latencies in networking and I/O.

Many customers moved immediately to Red Hat Enterprise Linux 6 for the latest in filesystem performance and options. This update updates our advanced networking storage offerings. FCoE, Data Center Briding and iSCSI offload allow networked storage to deliver the quality of service required.

Keeping pace with the latest hardware innovations, we worked with Intel to support the latest hot-plug processors and memory – as well as the latest NUMA architectures and PCI express 3.0.

Developers can now process memory with Valgrind improvements and learn even more about running processes with SystemTap. These enhancements have been integrated into the Eclipse IDE for a unified development experience.

Red Hat Enterprise Linux supports the entire data center architecture and major infrastructure projects like:

Moving to IPv6 is easier with optimized networking, firewall and DHCP/DNS services.
Intelligent application consolidation using Control Groups functionality for resource control of applications and virtual machines.
Managing application uptime using transparent proxy or High-availability Add-Ons, that can fail-over applications, services or virtual machines.
Tracking Red Hat Enterprise Linux deployments and subscriptions by using the new Subscription Manager, currently only available with 6.1 and for use with RHN
Planning user authentication and authorization with LDAP, kerberos, AD integration or Red Hat Enterprise Identity (IPA) services, now in Tech Preview

Courtesy: Redhat Official Website.

Ubuntu 11.04 is available in its official site.

2011-05-13T21:33:00.000-07:00

Features of Ubuntu 11.04 (Natty Narwhal)

The latest version of the popular Linux desktop distribution Ubuntu 11.04 has been released and available from the official project web site. This new version uses the Unity user interface instead of GNOME Shell as default desktop (user can switch back to classic Gnome desktop any time). New features since Ubuntu 10.10 includes – Banshee as the default music player, Mozilla Firefox 4, LibreOffice, Linux kernel v2.6.38.2, gcc 4.5, Python 2.7, dpkg 1.16.0, Upstart 0.9, X.org 1.10.1, Mesa 7.10.2, Shotwell 0.9.2, and Evolution 2.32.2.

User Quota Creation

2011-04-20T07:29:00.000-07:00

Step1: #vim /etc/fstab
add usrquota in the /home partition after defaults,usrquota
Step2: #mount -o remount /home
Step3: #quotacheck -cf /home
Step4: #quotaon /home
Step5: #repquota /home
Step6: #edquota pna - edit the quota for the user pna ( give the soft and hard limitations)
Step7: #repquota /home (It will show the quota for the user pna)

Adding kickstart file in the remote boot screen itself

2011-04-15T22:09:00.000-07:00

Edit the following file:

#vim /tftpboot/pxelinux.cfg/default

Add the follwoing line in the file:

label ks
kernel vmlinuz
append initrd=initrd.img ks=nfs:192.168.0.254:/var/ftp/pub/ks.cfg

Adding another OS in this file (example: rhel6):

label 6
kernel rhel6/vmlinuz
append initrd=rhel6/initrd.img ks=nfs:192.168.0.254:/var/ftp/pub/rhel6/ks.cfg

Compression & Backup

2011-04-11T05:17:00.000-07:00

gzip:
1.#seq 100000 > 1lakh.txt (creating a file with the content 100000)
2.#gzip -c 1lakh.txt > 1lakh.txt.gz (compressing the file)
3.#gzip -l 1lakh.txt.gz (showing the compression rate)
4.#gunzip 1lakh.txt.gz (uncompress the file)
5.#zcat 1lakh.txt.gz (view the content without decompressing)
or
#zcat 1lakh.txt.gz | less

bzip2: (best compression)
6.#bzip2 -c 1lakh.txt > 1lakh.txt.bz2 (compressing using algorithm bzip2)
7.#bzcat 1lakh.txt.bz2 (view the content without decompressing)
or
#bzcat 1lakh.txt.bz2 |less
8.#bunzip2 1lakh.txt.bz2 (decompressing using bzip2)

Zip:
9.#zip 1lakh.txt.zip 1lakh.txt (compressing using zip)
10.#unzip 1lakh.txt.zip (uncompress the file)

Tar & Gzip, Bzip2 (Tape Drive Archieve or backup):

create a directory special and put some contents in that.

11.#tar -cvf myfile.tar special/ (taking backup)

12.#tar -cvf myfile.tar 1lakh.txt.gz (adding another file in the same tar)

13.#tar -czvf myfile.tar.gz special/ (creating tar & gzip together)

14.#tar -cjvf myfile.tar.bz2 special/ (creating tar & bzip2 together)

15.#tar -tzvf myfile.tar.gz (viewing the gzip without extraction)

16.#tar -cjvf myfile.tar.bz2 special.save/ (viewing the files)

17.#tar -xvf myfile.tar.gz (extracting gzip file)

18.#tar -xvf myfile.tar.bz2 (extracting bzip2 file)

Google Chrome 10.0.648.204 works good in RHEL6

2011-04-05T22:21:00.000-07:00

Google Chrome 10.0.648.204 works good in RHEL6.

Steps to install Google Chrome to RHEL 6.

Step1:
Goto http://www.google.com/chrome/eula.html?platform=linux_fedora_i386 location

Step2: download the 32 bit .rpm (For Fedora/openSUSE) or 64 bit .rpm (For Fedora/openSUSE) with respect to your Operating System.

Step3: install the rpm by right clicking it.

Step4: Select the menu option as follows
Applications-> Internet -> Google Chorme.

Note: the rpm that is designed for Fedora and openSUSE works good for RHEL6 also.

RAID 5 Configuration in RHEL5.3

2011-03-31T05:04:00.000-07:00

Step 1: Create 3 partitions by using #fdisk /dev/sda (say /dev/sda6, /dev/sda7, /dev/sda8) and change the system id as fd (Linux raid autodetect)
Step 2: #partprobe or #reboot -f
Step 3: #mdadm -C /dev/md0 -l 5 -n 3 /dev/sda6 /dev/sda7 /dev/sda8
            #mkfs.ext3 /dev/md0
Step 4: #mkdir /raid5
            mount in /etc/fstab (/dev/md0 /raid5 ext3 defaults 0 0) (add an entry in /etc/fstab)
            #mount -a
Step 5: #mdadm --detail /dev/md0 (viewing the raid device)
            #cat /proc/mdstat (viewing the raid device configuration)
Step 6: #mdadm -f /dev/md0 /dev/sda8 (disabling device from the existing RAID)
           #mdadm -a /dev/md0 /dev/sda9 (adding a new device in the existing RAID)
           #mdadm -r /dev/md0 /dev/sda8 (for removing a device from the existing RAID)

HTTP or Apache Server with Authentication

2011-03-24T02:34:00.000-07:00

Step1: Install rpms
#rpm -ivh http*
or
#yum install http*

Step2: Setting up the configuration file
#vim /etc/httpd/conf/httpd.conf
ESC+shift+g

<Directory "/var/www/html/test"> create index.html file in this location
AuthType Basic
AuthName "password protected"
AuthUserFile /etc/httpd/testpass
Require user pna
<Directory>

Step3:
#htpasswd -c /etc/httpd/testpass pna
give the password two times
#service httpd restart
#chkconfig httpd on

Step4:
#elinks http://192.168.0.254/test (it will ask for username and password for accessing the website.)

Swap file creation & Swap partition creation

2011-03-16T04:19:00.000-07:00

Step:1 Adding virtual memory (adding swap file)

#dd if=/dev/zero of=/var/local/swapfile bs=1k count=1M (creating a file)
#mkswap /var/local/swapfile

Step:2 add an entry to /etc/fstab

/var/local/swapfile swap swap defaults 0 0

Step:3 enabling the swap partitions

#swapon -a (enabling all swap partitions)
#swapon -s (showing all swap partitions)

Creating swap partition

1.create a partition (eg:/dev/sda6)
2.#mkswap -L swap2 /dev/sda6 (creating a partition and label as swap2)

add an entry to /etc/fstab
LABEL=swap2 swap swap defaults 0 0
save and quit /etc/fstab

#swapon -a (enabling all swap partitions.)
#swapon -s (showing all swap partitions)

DHCP is working good in RHEL6

2011-03-11T21:57:00.000-08:00

Server Configuration:
Step1: install the following rpm

rpm -ivh dhcp-4.1.1-12.P1.el6.i686.rpm

Step 2: cp /usr/share/doc/dhcp-4.1.1/dhcpd.conf.sample /etc/dhcp/dhcpd.conf
Step 3: change the range of ip address as per your wish.
Step 4: service dhcpd restart
Step 5: chkconfig dhcpd on

Client Configuration:
Step 1: dhclient
Step 2: check the following file
            /etc/resolv.conf

Sample file: Copy and paste the specified location /etc/dhcp/dhcpd.conf and get the dhcp service

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

# option definitions common to all supported networks...
option domain-name "jetking.com";
option domain-name-servers ns1.example.org, ns2.example.org;

default-lease-time 600;
max-lease-time 7200;

# Use this to enble / disable dynamic dns updates globally.
#ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
log-facility local7;

# No service will be given on this subnet, but declaring it helps the
# DHCP server to understand the network topology.

subnet 192.168.0.0 netmask 255.255.255.0 {
range 192.168.0.1 192.168.0.10;
}

# This is a very basic subnet declaration.

subnet 10.254.239.0 netmask 255.255.255.224 {
range 10.254.239.10 10.254.239.20;
option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

subnet 10.254.239.32 netmask 255.255.255.224 {
range dynamic-bootp 10.254.239.40 10.254.239.60;
option broadcast-address 10.254.239.31;
option routers rtr-239-32-1.example.org;
}

# A slightly different configuration for an internal subnet.
subnet 10.5.5.0 netmask 255.255.255.224 {
range 10.5.5.26 10.5.5.30;
option domain-name-servers ns1.internal.example.org;
option domain-name "internal.example.org";
option routers 10.5.5.1;
option broadcast-address 10.5.5.31;
default-lease-time 600;
max-lease-time 7200;
}

# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

host passacaglia {
hardware ethernet 0:0:c0:5d:bd:95;
filename "vmunix.passacaglia";
server-name "toccata.fugue.com";
}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
host fantasia {
hardware ethernet 08:00:07:26:c0:a5;
fixed-address fantasia.fugue.com;
}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

class "foo" {
match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
}

shared-network 224-29 {
subnet 10.17.224.0 netmask 255.255.255.0 {
    option routers rtr-224.example.org;
}
subnet 10.0.29.0 netmask 255.255.255.0 {
    option routers rtr-29.example.org;
}
pool {
    allow members of "foo";
    range 10.17.224.10 10.17.224.250;
}
pool {
    deny members of "foo";
    range 10.0.29.10 10.0.29.230;
}
}

Call kickstart file from client machine

2011-02-27T22:32:00.000-08:00

Command for
Call kickstart file from client machine, if the server is running nfs
linux ks=nfs:192.168.0.254:/var/ftp/pub/ks.cfg

Installing fonts in Ubuntu 9.04

2011-02-23T04:20:00.000-08:00

Step 1: Copy the fonts to /usr/share/fonts or /home/.fonts directory
Step 2: Run the command sudo fc-cache -fv
Step 3: Check the font in any of the Open Office Packages.

PXE Server Configuration

2011-02-16T00:14:00.000-08:00

step1: copy the DVD into /var/ftp/pub

step2: vim /etc/exports
          /var/ftp/pub *(ro,sync)
          /tftpboot *(ro,sync)

step3: configure dhcp server
    vim /etc/dhcpd.conf
    insert the below two lines after
   #ignore-client updates

    allow booting;
    allow bootp;
    insert the below two lines after
    range

    filename "pxelinux.0";
    next-server 192.168.0.254;

step4: install tftp rpm
    vim /etc/xinetd.d/tftp
    disable=no

step5: disable iptables and tcp wrappers

step6: cp /usr/lib/syslinux/pxelinux.0 /tftpboot

step7: cd /tftpboot
    mkdir pxelinux.cfg
    cd /var/ftp/pub/isolinux
    cp * /tftpboot
    cd /tftpboot
    mv isolinux.cfg /tftpboot/pxelinux.cfg/default

step8: service portmap restart
    service nfs restart
            service vsftpd restart
            service network restart
            service dhcpd restart
            chkconfig tftp on
            chkconfig portmap on
            chkconfig nfs on
            chkconfig vsftpd on
            chkconfig network on
            chkconfig dhcpd on

User Permissions

2011-02-12T04:57:00.000-08:00

1.syntax: useradd username
eg: useradd bharat

2.syntax:ls -ld dirname
eg:ls -ld success

File permissions:

10 different attributes;
1-directory/file/link
2,3&4 - root permissions
5,6&7 - group permissions
8,9&10 - other permissions

permissions in terms of numbers:
4-read
2-write
1-execute

Example:
#chmod 766 success/
#chmod 777 success/
#chgrp -R bharat success
drwxrwxrwx 3 root bharat 4096 Feb 12 22:02 success/
#chown -R bharat success/
drwxrwxrwx 3 bharat bharat 4096 Feb 12 22:02 success/
#chmod u+x success/ - change mode as executable

Browsing File system

2011-02-12T04:51:00.000-08:00

1.copy - copying files
syntax:cp sourcefile destinationfile

2.rename -rename/move the files
i)syntax:mv sourcefile destinationfile (if the destination available it will be moved. Otherwise it will be renamed.)

3.create new files and manage nautilus
Applications-->system tools-->File browser

4.touch filename - command for creating dummy files / updating time stamp
5.cat filename - viewing the contents of a particular file
6.vim filname - editing the file.(saving esc+shift+:wq)
7.mkdir dir - creating a directory
8.cd dir -change directory
9.pwd :present working directory
10.cd - :previous working directory
11.cd :goto the home directory of the current user

12.Removing the file/directoy:
rmdir dirname - remove directory (if directory is empty)
rm -rf dirname - remove directory recursively (directory has some contents)

13.cd .. - going back the parent directory
14.syntax: file filename -for checking what type file the given is

Hardware configuration & Installation:I & II

2011-02-10T04:54:00.000-08:00

Hardware configuration & Installation:I

New hardware:
1. cdrom - automount/manual mount
2. pendrive    ""
3. printer
4. scanner

verification:
/dev/hdd on /media type iso9660 (ro)
#mount /dev/cdrom /media/ - linking/attaching
#umount /media/    - for unmounting/detaching.

mounting pendrive
#mount /dev/sdb1 /mnt/

unmounting pendrive:
#umount /mnt/

Harddisk categories
1.sata & scsi sda,sdb,sdc,& sdd Primary master, primary slave, secondary master & secondary slave
2.IDE harddisk
hda,hdb,hdc & hdd - primary master, primary slave, secondary master & secondary slave
3.Virtual harddisk
vda,vdb,vdc,vdd - primary master, primary slave, secondary master & secondary slave

Kudzu
Kudzu is a service that is used to check and mount new hardware.(camera,scanner)
#whereis kudzu    - location of the command kudzu

files for checking new hardware
/etc/sysconfig/hwconf
/etc/modprobe.conf
/etc/sysconfig/network-scripts/
/etc/X11/xorg.conf

kudzu
service kudzu status
service kudzu start
service kudzu stop
chkconfig kudzu on

Hardware configuration & Installation:II
1.mount the file system
2.mount ntfs file system
    i) read only mount
    11) read write mount
3.syntax of mount
#mount sourcepath mountpoint
eg: mount /dev/cdrom/ /mnt/

mount 192.168.0.254:/var/ftp/pub/ on /mnt type nfs (rw,addr=192.168.0.254
#fdisk -l |grep NTFS - for viewing ntfs file system only.