Monday, September 19, 2011

Nameserver Types

There are two nameserver configuration types:
Authoritative nameservers answer to resource records that are part of their zones only. This category includes both primary (master) and secondary (slave) nameservers.
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.

Wednesday, September 7, 2011

EXT4 features

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 ( 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."

Thursday, July 21, 2011

New in Red Hat Enterprise Linux 6

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

    High Availability Add-On

    High Availability add-on logoThe 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

    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
    The Conga application of Red Hat Enterprise Linux provides centralized configuration and management for the High Availability Add-On
    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 virtualizationVirtualization 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


    Friday, May 20, 2011

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

    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.

    Friday, May 13, 2011

    Ubuntu 11.04 is available in its official site.

    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, 1.10.1, Mesa 7.10.2, Shotwell 0.9.2, and Evolution 2.32.2.

    Wednesday, April 20, 2011

    User Quota Creation

    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)

    Friday, April 15, 2011

    Adding kickstart file in the remote boot screen itself

    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:

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

    label 6
    kernel rhel6/vmlinuz
    append initrd=rhel6/initrd.img ks=nfs:

    Monday, April 11, 2011

    Compression & Backup

    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)
    #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)
    #bzcat 1lakh.txt.bz2 |less
    8.#bunzip2 1lakh.txt.bz2  (decompressing using bzip2)

    9.#zip 1lakh.txt (compressing using zip)
    10.#unzip (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 (viewing the files)
    17.#tar -xvf myfile.tar.gz (extracting gzip file)
    18.#tar -xvf myfile.tar.bz2 (extracting bzip2 file)

    Tuesday, April 5, 2011

    Google Chrome 10.0.648.204 works good in RHEL6

    Google Chrome 10.0.648.204 works good in RHEL6.

    Steps to install Google Chrome to RHEL 6.

    Goto 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.

    Thursday, March 31, 2011

    RAID 5 Configuration in RHEL5.3

    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)

    Thursday, March 24, 2011

    HTTP or Apache Server with Authentication

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

    Step2: Setting up the configuration file
    #vim /etc/httpd/conf/httpd.conf

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

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

    #elinks (it will ask for username and password for accessing the website.)

    Wednesday, March 16, 2011

    Swap file creation & Swap partition creation

    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)

    Friday, March 11, 2011

    DHCP is working good in RHEL6

    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

    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 "";
    option domain-name-servers,;

    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.

    # 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 netmask {

    # This is a very basic subnet declaration.

    subnet netmask {
      option routers,;

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

    subnet netmask {
      range dynamic-bootp;
      option broadcast-address;
      option routers;

    # A slightly different configuration for an internal subnet.
    subnet netmask {
      option domain-name-servers;
      option domain-name "";
      option routers;
      option broadcast-address;
      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 "";

    # 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;

    # 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 netmask {
        option routers;
      subnet netmask {
        option routers;
      pool {
        allow members of "foo";
      pool {
        deny members of "foo";

    Sunday, February 27, 2011

    Call kickstart file from client machine

    Command for
    Call kickstart file from client machine, if the server is running nfs
    linux ks=nfs:

    Wednesday, February 23, 2011

    Installing fonts in Ubuntu 9.04

    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.

    Wednesday, February 16, 2011

    PXE Server Configuration

    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

        filename "pxelinux.0";

    step4: install tftp rpm
        vim /etc/xinetd.d/tftp

    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

    Saturday, February 12, 2011

    User Permissions

    1.syntax: useradd username
    eg: useradd bharat

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

    File permissions:

    10 different attributes;
    2,3&4 - root permissions
    5,6&7 - group permissions
    8,9&10 - other permissions

    permissions in terms of numbers:

    #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

    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 filename - viewing the contents of a particular file
    6.vim filname - editing the file.(saving esc+shift+:wq)
    7.mkdir dir - creating a directory dir -change directory
    9.pwd :present working directory - :previous working directory :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) ..    - going back the parent directory
    14.syntax: file filename -for checking what type file the given is

    Thursday, February 10, 2011

    Hardware configuration & Installation:I & II

    Hardware configuration & Installation:I

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

    /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 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

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

    Wednesday, February 9, 2011

    New Features in RHEL6

    1. ext4 file system is introduced.
    2. xen is removed and kernel virtualization machine (KVM) is introduced.
    3. neat command is removed.
    4. portmap service is removed.
    5. iscsi is introduced, which supports for SAN.
    6. rpmbuild is available, which is used to create our own rpms.
    7. File encyption is added.
    8. palimpsest is available for disk management.
    9. Virtual machine will run only on 64bit processors.
    10. postfix service is recommended instead of sendmail service.

    Thursday, January 20, 2011

    Wine works good in RHEL 5.3

    Search the below rpm and install it .(i.e., wine).
    Step1: rpm -ivh wine-core-1.1.9-1.el5.test.i386.rpm

    Step2: open the vlc-1.1.5-win32.exe via Wine Loader.

    Step3: Play the desireable video or audio file.

    Wednesday, January 19, 2011

    Transmission Bit Torrent Client works good in RHEL 5.3

    Google the below rpm and download it carefully. Then install the rpm as shows below.
    Step 1: rpm -ivh transmission-1.34-1.el5.i386.rpm
    Step 2: Applications-->Internet-->Transmission BitTorrent Client

    Red Hat Enterprise Linux 5.6 Now Available

    Highlights of Red Hat Enterprise Linux 5.6 include:
    • Hardware enablement
    • The release continues to enable new hardware from Red Hat partners, encompassing processors and chipsets launching in 2011, I/O (iSCSI & iSNS) and multimedia, combined with numerous driver updates. Red Hat Enterprise Linux 5.6 provides updated installation media to allow easier installation on new OEM platforms using the newly enabled hardware.
    • Virtualization improvements
    • Several virtualization feature updates are provided in Red Hat Enterprise Linux 5.6. These include support for sVirt (SELinux virtualization), which enables Mandatory Access Control (MAC) profiles to be applied to virtual guests, enhancing overall system security. Additionally, new I/O fencing capabilities enable Red Hat Enterprise Linux virtual guests configured with the High Availability (HA) Add-On to be supported when layered on a Red Hat Enterprise Virtualization infrastructure. This provides customers with greater flexibility when deploying highly available virtualized and cloud computing environments.
    • Updated Domain Name Service (DNS) packages
    • With updated DNS packages, Red Hat Enterprise Linux 5.6 improves the cryptographic signatures that are valuable for high-security installations, such as in the government sector and environments where signed DNS domains are expanding in importance.
    • Expanded PHP web application stack support
    • By incorporating the new PHP 5.3 release, Red Hat Enterprise Linux 5.6 provides customers with the ability to utilize the latest PHP technology prior to upgrading to Red Hat Enterprise Linux 6.
    • New printing capabilities
    • Red Hat Enterprise Linux 5.6 provides support for new printing capabilities by supporting the OpenVector Printer driver and by including support for the latest models of printers from HP.
    • Red Hat Enterprise Linux 6 backports
    • Red Hat Enterprise Linux 5.6 includes a number of features that bring some improvements introduced with the release of Red Hat Enterprise Linux 6 to 5.6. These include support for the Ext4 file system and incorporation of features, such as the System Security Services Daemon and gcc 4.4 compiler, that are compatible with the respective versions in Red Hat Enterprise Linux 6. Courtesy: