Installation of SVN plugin inside Eclipse , I will use subversive plugin here .

1. Go to Help->Software Updates.
2. Click on the “Available Software” tab.
3. Unfold the Ganymede->Collaboration Tools node, and , you will see the “SVN Team Provider (Incubation)” item , “0.7.1.I20080612-1500″. What you really need is the version from 2008-08-01.
4. Click on “Manage Sites…”.
5. Uncheck the “Ganymede” checkbox (http://download.eclipse.org/releases/ganymede)
6. Scroll down to find “http://download.eclipse.org/technology/subversive/0.7/update-site/”, select it and click “OK”.
7. You should be back on the “Available Software” tab, with only the subversive items present. Note that the version identifier is “0.7.3.I20080814-1500″.
8. Check the box, and click”install”. The install will be change to an update. Restart Eclipse at the end of the install.
9. Go to “Help->Software Updates”.
10. Choose the “Available Software” tab.
11. Click the “Add Site” button, and add “http://www.polarion.org/projects/subversive/download/eclipse/2.0/update-site/”.
12. Check the SVNKit Connectors and click “Install”. Restart Eclipse at the end of the install.
13. Subversive should be working !

Installation of SVN plugin inside Visual Studio IDE

This is very simple just install AnkhSvn exe from the site

http://ankhsvn.open.collab.net/downloads

Install this exe and restart Visual Studio .
This will work on Visual Studio 2005/05/10.

#rpm -Uvh ‘http://plone.lucidsolutions.co.nz/linux/centos/images/jpackage-utils-compat-el5-0.0.1-1.noarch.rpm

#yum update
# yum install tomcat6 tomcat6-webapps tomcat6-admin-webapps
# service tomcat6 start

binutils.i386
compat-gcc-7.3-2.96.128.i386
compat-gcc-c++-7.3-2.96.128.i386
compat-libstdc++-7.3-2.96.128.i386
compat-libstdc++-devel-7.3-2.96.128.i386
cpp.i386
gcc.i386
gcc-c++.i386
glibc.i386
glibc-common.i386
glibc-devel.i386
glibc-headers.i386
glibc-kernheaders.i386
libstdc++.i386
libstdc++-devel.i386
libaio
libai-devel.i386
pdksh.i386
setarch.i386
sysstat.i386

Download the Oracle 10gR2 from ,

http://www.oracle.com/technology/software/products/database/oracle10g/index.html

Preinstallation Steps:
1. Edit /etc/hosts file

2. Edit /etc/sysctl.conf
#kernel.shmall = 2097152
#kernel.shmmax = 2147483648
kernel.shmmni = 4096
# semaphores: semmsl, semmns, semopm, semmni
kernel.sem = 250 32000 100 128
#fs.file-max = 65536
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default=262144
net.core.rmem_max=262144
net.core.wmem_default=262144
net.core.wmem_max=262144

3. Run the following command to change the kernel parameters

/sbin/sysctl -p

4. Add the following security parameter
in /etc/security/limits.conf

oracle soft nproc 2047
oracle hard nproc 16384
oracle soft nofile 1024
oracle hard nofile 65536

5. Edit /etc/pam.d/login and add following line

session required pam_limits.so

6. SElinux and firewall should be turned off

check /etc/selinux/config

SELINUX=disabled

7. Creating following users and Groups

groupadd oinstall
groupadd dba
groupadd oper

useradd -g oinstall -G dba oracle
passwd oracle

8. Oracle will be installed in the following Directories

#mkdir -p /u01/app/oracle/product/10.2.0/db_1
#chown -R oracle.oinstall /u01

9. Login as Root user on the machine in GUI console and execute
#xhost +
This will enable other users to use X console

10. Take backup of the file /etc/redhat-release to /etc/redhat-release.original

and edit /etc/redhat-release
#echo “redhat-4″> /etc/redhat-release

11. Edit the /home/oracle/.bash_profile
add the following lines

# Oracle Settings
TMP=/tmp; export TMP
TMPDIR=$TMP; export TMPDIR

ORACLE_BASE=/u01/app/oracle; export ORACLE_BASE
ORACLE_HOME=$ORACLE_BASE/product/10.2.0/db_1; export ORACLE_HOME
ORACLE_SID=TSH1; export ORACLE_SID
ORACLE_TERM=xterm; export ORACLE_TERM
PATH=/usr/sbin:$PATH; export PATH
PATH=$ORACLE_HOME/bin:$PATH; export PATH

LD_LIBRARY_PATH=$ORACLE_HOME/lib:/lib:/usr/lib; export LD_LIBRARY_PATH
CLASSPATH=$ORACLE_HOME/JRE:$ORACLE_HOME/jlib:$ORACLE_HOME/rdbms/jlib; export CLASSPATH

if [ $USER = "oracle" ]; then
if [ $SHELL = "/bin/ksh" ]; then
ulimit -p 16384
ulimit -n 65536
else
ulimit -u 16384 -n 65536
fi
fi

12. Log into the oracle user. If you are using X emulation then set the DISPLAY environmental variable:

DISPLAY=:0.0; export DISPLAY

13. Copy the file 10201_database_linux32.zip into oracle user home directory ,i.e, /home/oracle

and unzip the file.

14. Now the time to start installation

when u extact the file it will create a database directory.
$cd database
$./runInstaller
This will start Oracle Universal Installer

15 . In Oracle Universal Installer

a. Select Advanced Installation
b. Here Specify Inventory Directory and Credentials

Values are : /u01/app/oracle/oraInventory
and OS group name will be onistall

c. Select Installation Type
Enterprise Edition
d. Specify Home Details
Name; db_1
Path ; /u01/app/oracle/product/10.2.0/db_1

e. Product Specific Prerequisite checks

This should come passed ,otherwise select user varified

f. Select Configuration Options

Create Database

g. Select Database configuration

General Purpose

h. Specify Database configuration options
Global Database Name: TSH1
SID : TSH1

i. Select Database management options

use database control for database management

j. Specify Database Storage Option
File System
location /u01/app/oracle/oradata

k. Specify Backup and Recovery Options

Do not enable

l. Specify Database Schema Passwords

give a password which you must remember .

m. Summery and install
when the installation finishes it will show
Database Configuration Assistant
click ok
Now it will give you 2 scripts which must be run as root
#/u01/app/oracle/oraInventory/orainstRoot.sh
#/u01/app/oracle/product/10.2.0/db_1/root.sh

This is the end of installation part.

16. Post installation Steps

Just copy back
#cp /etc/redhat-release.original /etc/redhat-release

Edit the file /etc/oratab , In last change to Y

TSH1:/u01/app/oracle/product/10.2.0/db_1:Y

17. Autostart and Stop Script , login as root and create a script

This script is required to automatically start/stop  Oracle database

#vim /etc/init.d/dbora

ORA_HOME=/u01/app/oracle/product/10.2.0/db_1
ORA_OWNER=oracle

if [ ! -f $ORA_HOME/bin/dbstart ]
then
    echo "Oracle startup: cannot start"
    exit
fi

case "$1" in
    'start')
        # Start the Oracle databases:
        # The following command assumes that the oracle login
        # will not prompt the user for any values
        su - $ORA_OWNER -c "$ORA_HOME/bin/dbstart $ORA_HOME"
        ;;
    'stop')
        # Stop the Oracle databases:
        # The following command assumes that the oracle login
        # will not prompt the user for any values
        su - $ORA_OWNER -c "$ORA_HOME/bin/dbshut $ORA_HOME"
        ;;
esac

---------------------------------
#chmod 750 /etc/init.d/dbora

#chkconfig --level 345 dbora on

Now we have created the script which will start/stop with Operating system 

#/etc/init.d/dbora stop

#/etc/init.d/dbora start

Note : you may get the listener waring message while starting oracle db

Failed to auto-start Oracle Net Listener using /ade/vikrkuma_new/oracle/bin/tnslsnr

To Resolve the issue ,login as oracle user and  change the file $ORACLE_HOME/bin/dbstart

Nearly 78 line

ORACLE_HOME_LISTNER=/ade/vikrkuma_new/oracle

Change to

ORACLE_HOME_LISTNER=$ORACLE_HOME

18. As oracle user Login in shell

$sqlplus
usename : SYSTEM
password : givenbyyou

Some of the Reference taken from
1. http://dearlinux.wordpress.com/2010/07/01/installing-oracle-database-10g-release-2-on-linux-rhel-5-part-2/
2. http://www.oracle-base.com/articles/10g/OracleDB10gR2InstallationOnRHEL5.php
3. http://ivan.kartik.sk/oracle/install_ora10gR2_redhat.html

When the daemon of xend stops ,the cron task who is
/etc/cron.hourly/mcelog.cron can’t read /sys/hypervisor/uuid.It leads to D
status of “cat /sys/hypervisor/uuid ” which results in high load average

Version-Release number of selected component (if applicable):
In RHEL5.4 for 64 bits x86_64 xen kernel.

How reproducible:
In xen kernel,make the daemon of xend stop.

Steps to Reproduce:
1.#service xend stop
2.#top  (see the load average by hours)
3.#ps aux |grep “^D” (there are lots of “D” status process)

Actual results:
See the result of ‘ps’ ,we will find there are a lot of “D” state
process.Theses process are waiting for cat /sys/hypervisor/uuid.And the load
average become more and more high.
Expected results:

When the daemon of xend stops, the process can read /syst/hypervisor/uuid.The
load average is not high by hours.

[root@server ~]# ps aux | grep /sys/hypervisor/uuid
root       708  0.0  0.0   3796   400 ?        D    05:00   0:00 cat /sys/hypervisor/uuid
root      2313  0.0  0.0   3796   396 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root      4477  0.0  0.0   3796   400 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root      5813  0.0  0.0   3796   396 ?        D    06:00   0:00 cat /sys/hypervisor/uuid
root      6140  0.0  0.0   3796   396 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root      6502  0.0  0.0   3796   400 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root      7403  0.0  0.0   3796   396 ?        D    00:00   0:00 cat /sys/hypervisor/uuid
root      9434  0.0  0.0   3796   396 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root     10902  0.0  0.0   3796   396 ?        D    07:01   0:00 cat /sys/hypervisor/uuid
root     11499  0.0  0.0   3796   400 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root     12471  0.0  0.0   3796   400 ?        D    01:00   0:00 cat /sys/hypervisor/uuid
root     14525  0.0  0.0   3796   396 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root     16579  0.0  0.0   3796   400 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root     16630  0.0  0.0   3796   400 ?        D    08:01   0:00 cat /sys/hypervisor/uuid
root     17055  0.0  0.0  58904   464 ?        D    08:07   0:00 cat /sys/hypervisor/uuid
root     17562  0.0  0.0   3796   396 ?        D    02:00   0:00 cat /sys/hypervisor/uuid
root     18017  0.0  0.0  61160   748 pts/2    S+   08:17   0:00 grep /sys/hypervisor/uuid
root     19598  0.0  0.0   3796   396 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid
root     21655  0.0  0.0   3796   400 ?        D    Aug13   0:00 cat /sys/hypervisor/uuid

Due to this load average is very -2 high ( load average: 22.09, 22.07, 22.01). After stopping xend #service xend stop and i have started again and all cat /sys/hypervisor/uuid process stopped and i have stopped this process again.

After restarting xend services, all /sys/hypervisor/uuid processes killed and also load average was coming donw
[root@server ~]# ps aux | grep /sys/hypervisor/uuid
root     21666  0.0  0.0  61160   736 pts/0    S+   08:30   0:00 grep /sys/hypervisor/uuid
[root@server ~]#

[root@server ~]# uptime
08:30:26 up 22:03,  1 user,  load average: 2.35, 14.47, 19.67
[root@server ~]#

Thanks
Manoj

Note: Before going to upgrade your database take a backup of your database and /etc/my.cnf file.

Now find out the current packages Installed on your system by

[root@localhost~]# rpm –qa | grep mysql
mysqlclient10-3.23.58-4.RHEL4.1
mysql-devel-4.1.7-4.RHEL4.1
mysql-server-4.1.7-4.RHEL4.1
mysql-4.1.7-4.RHEL4.1
mod_auth_mysql-2.6.1-2.1
mysql-bench-4.1.7-4.RHEL4.1
libdbi-dbd-mysql-0.6.5-10.RHEL4.1
php-mysql-4.3.9-3.1

Once you find out the packages now its time to remove the unwanted packages mainly server and client, but the communication packages and authentication packages can be remain as it is; if require you can remove those also.

I have selected the following packages to remove, remove it by following command

rpm -e –nodeps mysql-devel-4.1.7-4.RHEL4.1
rpm -e –nodeps mysql-server-4.1.7-4.RHEL4.1
rpm -e –nodeps mysql-4.1.7-4.RHEL4.1
rpm -e –nodeps mysql-bench-4.1.7-4.RHEL4.1
rpm -e –nodeps mysql-bench-4.1.7-4.RHEL4.1

Once you have removed the mysql packages, restart the server (Not necessary but better to do)
Before restarting the server check the folder name mysql on location /var/lib; this folder is actual repository of your mysql databases.

After restarting deploy the mysql 5 packages by issuing following command

rpm -ivh MySQL-server-community-5.0.51a-0.rhel4.i386.rpm
rpm -ivh MySQL-client-community-5.0.51a-0.rhel4.i386.rpm
rpm -ivh MySQL-shared-compat-5.0.51a-0.rhel4.i386.rpm
rpm -ivh MySQL-devel-community-5.0.51a-0.rhel4.i386.rpm

Here you have upgrade the mysql 4 to mysql 5. Now try to log in to the database by using your previously defined database user and password.

[root@server html]# rm -f *
-bash: /bin/rm: Argument list too long

OR

In our case (Number of files in the folder is around 1 million ) if we run ls or other command, linux shell prompt hung and we need to start new terminal.

What to do when this occurs? You have to combine several Linux commands in order to empty this folder. Here is the command you should use; I will explain what does it do below.

[root@server html]# ls | grep .| xargs rm

This will do the following: the first command ls outputs the list of files. The output is being sent to grep command so you won’t see it in your console. Grep searches for files with “.” symbol (in the example given I think that all your files have so named extension – filenames contain a dot. So grep will extract all the file names that contain a dot and will throw them to the next function – xargs. xargs accepts these filenames and deletes them one by one. This allows to reduce server load and gives us the possibility to delete multiple files in one folder that are no longer necessary.

Thanks
Manoj

1. This is the most basic configuration where anyone will have unrestricted access to the repos. Location is the name that will be used in the browser address bar. In this example it will be ‘http://localhost/svn/repos’

2. This is a configuration with username and password for the client

DAV svn

SVNListParentPath on

SVNParentPath /usr/local/svn/

AuthType Basic

AuthName “Subversion repositories”

AuthUserFile “/etc/httpd/conf.d/svnuserconf”

Require valid-user

1.
* htpasswd -cm /etc/httpd/conf.d/svnuserconf admin — This command is not needed for the first configuration. To create the first user with password
* htpasswd -m /etc/httpd/conf.d/svnuserconf pawan — use this command to add another user
2. Configure your repository
* mkdir /usr/local/svn — create folder svn
* cd /usr/local/svn — change diectory to the newly created svn directory
* svnadmin create repos — create svn repository named repos
* chown apache.apache -R repos — change ownership of ‘repos’ to apache
* /etc/init.d/httpd restart — restart apache
* If you are running different apache change port no from conf file.
3. Open you browser and type ‘http://localhost/svn/repos’. You can see that a page with ‘Revision 0:/’ will appear. Congratulation, you just completed the setup for svn server

Thanks
Manoj Chauhan

For blocked I/O, the dd command has no competition in the standard tool set. One could write a custom utility to do specific I/O or formatting but, as dd is already available almost everywhere, it makes sense to use it.

Like most well-behaved commands, dd reads from its standard input and writes to its standard output, unless a command line specification has been given. This allows dd to be used in pipes, and remotely with the rsh remote shell command.

Unlike most commands, dd uses a keyword=value format for its parameters. This was reputedly modeled after IBM System/360 JCL, which had an elaborate DD ‘Dataset Definition’ specification for I/O devices. A complete listing of all keywords is available from GNU dd with

# dd –help

For more options check dd man page

Using dd you can create backups of an entire harddisk or just a parts of it. This is also usefull to quickly copy installations to similar machines. It will only work on disks that are exactly the same in disk geometry, meaning they have to the same model from the same brand.

full hard disk copy

dd if=/dev/hdx of=/dev/hdy
dd if=/dev/hdx of=/path/to/image
dd if=/dev/hdx | gzip > /path/to/image.gz

Hdx could be hda, hdb etc. In the second example gzip is used to compress the image if it is really just a backup.

Restore Backup of hard disk
copy

dd if=/path/to/image of=/dev/hdx

gzip -dc /path/to/image.gz | dd of=/dev/hdx

MBR backup

In order to backup only the first few bytes containing the MBR and the partition table you can use dd as well.

dd if=/dev/hdx of=/path/to/image count=1 bs=512

MBR restore

dd if=/path/to/image of=/dev/hdx

Add “count=1 bs=446″ to exclude the partition table from being written to disk. You can manually restore the table.

Thanks
Manoj

Thanks
Pankaj Joshi

Thanks
Pankaj

In this article, I’ll show you how to get ReiserFS running under a typical Linux distribution. I’ll also share lots of technical information on a variety of topics, such as performance considerations and more. Since I’ll be covering installation first, I recommend that you read this article in its entirety before following the installation instructions. That way, you’ll have all the technical notes in the back of your head as you start getting ReiserFS running on your systems, allowing you to make any necessary adjustments along the way.

The Search For A Good Kernel

To enable ReiserFS on your system, you’ll first need to find a suitable kernel. At the time this article was orginally written (way back in 2001,) finding a suitable kernel for running ReiserFS required some effort, as ReiserFS was still an experimental filesystem. However, these days ReiserFS is no longer considered to be experimental and it’s quite easy to find a kernel that supports ReiserFS. Unfortunately, Red Hat has removed ReiserFS support from the official Red Hat Enterprise Linux kernel, but it available in the stock Linux kernel sources, as well as various RHEL-based kernels.

If for some reason you are using a 2.4 kernel version, try to avoid early revisions of the kernel and use something that is fairly recent, like 2.4.30 or higher.

Are You Ready?

The first step in using ReiserFS is to make sure that your kernel has ReiserFS support available. To do this, type:

cat /proc/filesystems

If you see “reiserfs” listed in the resultant list, then reiserfs support is currently available. You’re ready to go!

Now, what happens if you don’t see ReiserFS support listed? Well, it’s possible that it’s actually there, but available as a kernel module and not yet loaded. To see if this is the case, first become the root user if you aren’t root already, and type:

# modprobe reiserfs

Was modprobe able to load the reiserfs module? Run the cat /proc/filesystems command again and see if reiserfs is in the list. If it is, great! If not, then it looks like you are going to need to either upgrade to a kernel with ReiserFS support or recompile your existing kernel, if you enjoy doing that kind of thing.

If you’re up for recompiling your own kernel, here’s how you’d go about enabling ReiserFS. First, type make menuconfig in your kernel source tree. Under the Code maturity level options section, make sure that the Prompt for development and/or incomplete code/drivers option is enabled if you are using a 2.4 kernel. Then, head over to the File systems section, and enable ReiserFS support. It’s recommended that you enable ReiserFS support to be compiled directly into your kernel (not as a module.) You may enable the extra ReiserFS capabilities if you wish. Now, save your settings, compile your kernel (make dep (for kernel 2.4 only); make bzImage; make modules; make modules_install) and configure your boot loader to load the new ReiserFS-enabled kernel.
Important:
It’s always a good idea to save your current kernel and configure your boot loader so that you can boot with your original kernel, just in case your new kernel doesn’t work.

Installing the Tools

Now, before you potentially reboot with a brand-new, ReiserFS-enabled kernel, we need to make sure that you have the “reiserfsprogs” tools installed. Most modern distributions will have these tools available. To determine if they are installed, run the following command as root:

# reiserfsck

Was it found? If so, great! This means that the reiserfsprogs are installed and available. If they aren’t available, I recommend using your distribution’s package manager to track down these tools and install them. Once the tools are installed, now would be a good time to reboot to enable a new ReiserFS-enabled kernel if you installed one.

Creating and Mounting the Filesystem

Once rebooted, you’ll be able to create a ReiserFS filesystem on an empty partition as follows:

# mkreiserfs /dev/hdxy

In the above example, /dev/hdxy should be a device node corresponding to a free partition. Mount it as you would any other filesystem:

# mkdir /mnt/reiser
# mount /dev/hdxy /mnt/reiser

And, if you’d like to add a ReiserFS filesystem to your /etc/fstab file, simply set the freq and passno fields to 0, as follows:

/dev/hdc1  /home  reiserfs  defaults  0  0

From this point forward, your ReiserFS filesystems should act identically to their ext2 counterparts, except that you’ll no longer need to worry about long fsck times, and overall performance will be much better — especially for small files.

ReiserFS Technical Notes

Filesystem Stability

With a modern kernel, ReiserFS is generally just as reliable as ext2 or ext3. As with all filesystems, a spattering of older kernels had some filesystem corruption bugs in them and should be avoided. However, if you are relying on your Linux distribution’s selection of kernels, then you should not experience any issues with ReiserFS.

No dump/restore

Yes, it’s true; ReiserFS does not yet have a dump and restore implementation. If you want to user ReiserFS and happen to be a dump fan, you’ll have to find some alternate way of backing data. In reality, this turns out to be a non-issue, since 2.4+ kernels are incompatible with dump and restore in the first place. For more information on the dump/kernel incompatibility, read the LKML posting by Linus Torvalds where he says that “Dump was a stupid program in the first place. Leave it behind.”

Performance Issues

While ReiserFS generally blows the socks off ext2, ReiserFS does have a few special-case performance weaknesses. The first is sparse file performance. ReiserFS sparse file performance will be significantly worse than ext2. This will change at some point, when the Namesys developers get around to optimizing that part of ReiserFS for ReiserFS 4. Until then, ext2 is a better solution for applications that place heavy demands on sparse (small) files.

Performance Tweaks

Fortunately, there are a couple of easy general performance tweaks you can use to make these problems less severe. The first is to mount your ReiserFS filesystem with the noatime mount option (a mount option that’s available for other filesystems as well as ReiserFS). As you probably know, UNIX systems record an atime, or access time, for each object on the filesystem that gets updated every time a file is read. For most people, the atime stamp isn’t very useful and hardly any applications (none I can think of) rely on the atime for any critical task. For this reason, it can usually be safely turned off, which gives a nice all-around performance boost. Generally, unless you specifically know that you need atime support, you should be mounting your filesystems with the noatime option. Use an /etc/fstab entry like this:

/dev/hdc1  /home  reiserfs  noatime  0  0

In first ReiserFS article, I mentioned that ReiserFS has a special feature called “tail packing”. In ReiserFS lingo, “tails” are files that are smaller than a filesystem block (4k) or the trailing portions of files that don’t quite fill up a complete filesystem block. ReiserFS has really excellent small-file performance because it is able to incorporate these tails into its b*tree (its primary organizational data structure) so that they are really close to the stat-data (ReiserFS’ equivalent of an i-node). However, since tails don’t fill up a complete block, they can waste a lot of disk space (relatively speaking, of course). To solve this problem, ReiserFS uses its “tail packing” functionality to squish tails into as small a space as possible. Generally, this allows a ReiserFS filesystem to hold around 5% more than an equivalent ext2 filesystem.

Tail Packing Pros and Cons

However, tail packing also has its disadvantages. For one, it does give you a small but significant performance hit. Fortunately, the ReiserFS guys anticipated that some people would be willing to sacrifice around 5% of their disk capacity for a little extra performance, so they created the notail mount option. When a filesystem is mounted with this option, tail packing will be turned off, giving you greater speed and less storage capacity. In general, filesystem performance freaks mount their filesystems with both notail and noatime enabled, producing a noticeable performance improvement:

/dev/hdc1  /home  reiserfs  noatime,notail  0  0

Even if you want to save some disk space, there are times when temporarily mounting your filesystem with the notail option can be a good thing. In particular, some older boot-loaders have problems loading kernels that were created on a ReiserFS filesystem with tail packing enabled. If you’re using a LILO earlier than version 21.6, you’ll have this problem. You will also have problems with old versions of GRUB, which will not be able to load its stage1 and stage1_5 files. If you’re already experiencing this problem, you can fix it by mounting the filesystem with the notail option, moving the files to another filesystem, and then moving them back. When they’re recreated, they won’t have tails. Also, remember that you can easily remount a filesystem (with new options) without unmounting it. This particular example remounts the root filesystem with the notail option:

# mount / -o remount,notail

Conclusion

I’ve found ReiserFS to be a truly incredible filesystem, offering oodles of small file performance and great (normally better than ext2) regular file performance. For example, updates to source code repositories using cvs and ReiserFS have been observed to complete in only fifteen seconds, where the same source code tree takes about two minutes to update with ext2. ReiserFS makes many peoples’ lives more pleasant, and allows servers to handle large amounts of simultaneous IO without thrashing hard drives and negatively affecting interactive performance.

In future articles, I hope to take a look at Reiser4, a completely new (and incompatible) version of ReiserFS which sports some interesting new capabilities.

Repairing ReiserFS file system with reiserfsck

The idea and commands in this article submitted by Jacques Wagener via email. In his own words, “After nuking my partition by accident (and through my stupidity) I was really disappointed in myself, especially in losing my bookmarks and rss-feeds”. The following article is based upon our email communication. I am just putting them as an article.

We have already written about ext2/ext3 file repair using fsck and other utilities. Linux comes with different filesystems and different repair utilities. To repair a ReiserFS filesystem you need to run reiserfsck command, which is a checking tool for the ReiserFS filesystem (just like fsck command for ext2/ext3 file system).

Reiserfsck searches for a Reiserfs filesystem on a device, replays any necessary transactions, and either checks or repairs the file system. ReiserFS saves data or log in a special file for pending disk updates and later on it commit updates to disk resulting into very good filesystem consistency.

Step # 1: Install reiserfsck

You need to install reiserfsprogs package, which includes reiserfsck user level tools for ReiserFS filesystems.
# apt-get install reiserfsprogs

Or if you are using RedHat/Fedor Core Linux:
# yum install reiserfsprogs

Step # 2: Backup partition/disk

Take system down to runlevel 1.
# init 1

Unmount /dev/sda1 (if it is still mounted as read/write only):
# umount /dev/sda1; umount /dev/sda2

Before using any one of the following command you are strongly advised to make a backup copy of the whole partition using dd or ddrescue (recommended) command.
# ddrescue /dev/sda /dev/sdb

OR use dd command:
# dd if=/dev/sda of=/dev/sdb conv=noerror
Step # 3: Check filesystem consistency

Above command makes a backup of your drive. Next check filesystem consistency which will reports problem to you with the following command (assuming that /dev/sda1 is your partition):
# reiserfsck –check /dev/sda1

If you get an error Bad root block 0If you get following message:
Running with –rebuild-tree is required

Then you need to run following command rebuilds the entire filesystem tree using leaf nodes found on the device (this is nothing but indication of corrupted :
# reiserfsck –scan-whole-partition –rebuild-tree /dev/sda1

Where,

* –scan-whole-partition: This option causes –rebuild-tree to scan the whole partition but not only the used space on the partition. You should always use this option with –rebuild-tree.
* –check: Checks filesystem consistency and reports, but does not repair any corruption that it finds.
* –rebuild-tree: This option rebuilds the entire filesystem tree using leaf nodes found on the device. Once you passed this option, do not stop or interrupt building operating.

Recovering corrupted superblock

Each file system has a superblock, which contains information about file system such as:

* File system type
* Size
* Status
* Information about other metadata structures

If this information lost, you are in trouble (data loss) so Linux maintains multiple redundant copies of the superblock in every file system.

During check (reiserfsck –check /dev/sda1) if you get an error superblock was missing, use following command to fix superblock:
# reiserfsck –rebuild-sb /dev/sda1

Where,

* –rebuild-sb: This option recovers the superblock on a Reiserfs partition. Normally you only need this option if mount reports “read_super_block: can’t find a reiserfs file system”.

Caution: Do not run above command twice on same drive. You will damage your partition (data).
Final note

Next logical step is mount your partition /dev/sda1 and check for your data:
# mkdir -p /mnt/data
# mount /dev/sda1 /mnt/data
# cd /mnt/data
# ls
# ls lost+found/ -l

lost+found is a special directory where recovered files are kept by Linux/reiserfsck. You can examine these files and restore the data.

Better backup entire partition using tar or ssh session:
# tar cvf /dev/nst0 /mnt/data

OR use scp to dump data to remote system:
# scp -r /mnt/data you@myserver.com:/backup

Thanks
Manoj Chauhan

The FEDERATED storage engine enables data to be accessed from a remote MySQL database on a local server without using replication or cluster technology. When using a FEDERATED table, queries on the local server are automatically executed on the remote (federated) tables. No data is stored on the local tables.

federated table in action

check if the federated engine is enabled

Mysql > show engines;

+————+———+—————————————————————-+
| Engine | Support | Comment |
+————+———+—————————————————————-+

| InnoDB | YES | Supports transactions, row-level locking, and foreign keys |
| MyISAM | DEFAULT | Default engine as of MySQL 3.23 with great performance |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) |
| CSV | YES | CSV storage engine |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables |
| FEDERATED | YES | Federated MySQL storage engine |
| ARCHIVE | YES | Archive storage engine |
| MRG_MYISAM | YES | Collection of identical MyISAM tables |
+————+———+—————————————————————-+

if it is not enabled go to /etc/my.cnf add federated=ON int the [mysqld] section and restart the MySQL .

Creating original table on remote server

CREATE TABLE test_table (
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(32) NOT NULL DEFAULT ”,
other INT(20) NOT NULL DEFAULT ’0′,
PRIMARY KEY (id),
INDEX name (name),
INDEX other_key (other)
)
ENGINE=MyISAM
DEFAULT CHARSET=latin1;

Create table on the local server

Two methods

1) Creating a FEDERATED Table Using CONNECTION

CREATE TABLE test_table(
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(32) NOT NULL DEFAULT ”,
other INT(20) NOT NULL DEFAULT ’0′,
PRIMARY KEY (id),
INDEX name (name),
INDEX other_key (other)
)
ENGINE=FEDERATED
DEFAULT CHARSET=latin1
CONNECTION=’mysql://fed_user@remote_host:9306/federated/test_table’;

more details can be checked on http://dev.mysql.com/doc/refman/5.1/en/federated-create-connection.html

2)Creating a FEDERATED Table Using CREATE SERVER

For example, to create a server connection identical to the CONNECTION string:

CREATE SERVER fedlink
FOREIGN DATA WRAPPER mysql

This server name is used while creating the federated table in CONNECTION

CREATE TABLE test_table (
id INT(20) NOT NULL AUTO_INCREMENT,
name VARCHAR(32) NOT NULL DEFAULT ”,
other INT(20) NOT NULL DEFAULT ’0′,
PRIMARY KEY (id),
INDEX name (name),
INDEX other_key (other)
)
ENGINE=FEDERATED
DEFAULT CHARSET=latin1
CONNECTION=’fedlink/test_table’;

more details can be checked at http://dev.mysql.com/doc/refman/5.1/en/federated-create-server.html

Access the data of the federated table on local server

mysql>use test ;

mysql>select * from test_table ;

federate table acts as a local table and all the select and DML operations can be done as if the table is lying on the local server ,
please note that no actual data is stored on the local sever.

now we can have the cross MySQL server data access

mysql > select * from localtable join test_table on localtable.id =test_table.id ;

Important things to remember

• FEDERATED tables may be replicated to other slaves, but you must ensure that the slave servers are able to use the user/password combination that is defined in the CONNECTION string (or the row in the mysql.servers table) to connect to the remote server.
• The remote server must be a MySQL server.
• The remote table that a FEDERATED table points to must exist before you try to access the table through the FEDERATED table.
• The FEDERATED storage engine supports SELECT, INSERT, UPDATE, DELETE, TRUNCATE TABLE, and indexes. It does not support ALTER TABLE, or any Data Definition Language statements that directly affect the structure of the table, other than DROP TABLE. The current implementation does not use prepared statements. Transactions are not supported.
• There is no way for the FEDERATED engine to know if the remote table has changed. The reason for this is that this table must work like a data file that would never be written to by anything other than the database system. The integrity of the data in the local table could be breached if there was any change to the remote database.
• Any DROP TABLE statement issued against a FEDERATED table drops only the local table, not the remote table.
• FEDERATED tables do not work with the query cache.

Thanks
Pankaj Joshi

IndexIgnore */* (It will stop files listing for specific folder)

# deny access to all files of folder

Order allow,deny
Deny from all
Satisfy All

Forbidding a particular file:

You can forbid a particular file using its name and extension.

order allow,deny
deny from all

Need to monitor Linux server performance? Try these built-in command and a few add-on tools. Most Linux distributions are equipped with tons of monitoring. These tools provide metrics which can be used to get information about system activities. You can use these tools to find the possible causes of a performance problem. The commands discussed below are some of the most basic commands when it comes to system analysis and debugging server issues such as:

1. Finding out bottlenecks.
2. Disk (storage) bottlenecks.
3. CPU and memory bottlenecks.
4. Network bottlenecks.

Newer Linux kernels have per-process I/O accounting and you can use the iotop tool to find out what’s performing I/O, but in many cases I’m trying to find the source of an I/O problem in an older kernel. I found sort of a hack-ish way to do that today, while trying to figure out why a system was basically unresponsive.

I found a post on Stack Overflow that showed a way you can get per process I/O statistics from the kernel even in older kernels. I adapted this to my needs, and wrote a little script.

Here’s how you use it. First, get it:

wget http://aspersa.googlecode.com/svn/trunk/iodump

Then turn on kernel messages about I/O:
echo 1 > /proc/sys/vm/block_dump

This makes the kernel start writing messages about every I/O operation that takes place. Now all you have to do is get those messages and feed them into my script:

while true; do sleep 1; dmesg -c; done | perl iodump

Wait a little while, then cancel the script. The results should look something like the following:

[root@manoj]# while true; do sleep 1; dmesg -c; done | perl iodump

Please wait for some time to get the stats from the dmesg and after 4 to 5 minute, please press Ctrl+c to abort the recording and below stats will come to screen.

# Caught SIGINT.
TASK                   PID      TOTAL       READ      WRITE      DIRTY DEVICES
kjournald              442       2849          0       2849          0 dm-0
nfsd                 29036       2731        217       2514          0 dm-0
nfsd                 29041       2495        111       2384          0 dm-0
nfsd                 29037       2120         74       2046          0 dm-0
nfsd                 29039       1996         94       1902          0 dm-0
nfsd                 29038       1380        110       1270          0 dm-0
nfsd                 29040        727        109        618          0 dm-0
pdflush              29423        234          0        234          0 dm-0
nfsd                 29042         89         89          0          0 dm-0
nfsd                 29035         87         87          0          0 dm-0
bash                 19067          2          2          0          0 dm-0
perl                 19066          2          2          0          0 dm-0
bash                 19068          1          1          0          0 dm-0
httpd                16476          1          1          0          0 dm-0

I deliberately generated a bunch of I/O by deleting my Firefox history and cache. If i see the above stats, it shows that NFSD (NFS Deamon) is doing lot’s of I/O and write operation is very -2 high.

Why not write a single script to do everything required, something like:

We can use below shell script to get the same stats, first it will turn on kernel messages about I/O after stats it will turn off kernel messages about I/O, as it is not good practice to keep kernel messages about I/O on.

#!/bin/sh
dmesg -c
/etc/init.d/klogd stop
echo 1 > /proc/sys/vm/block_dump

# allow 30 seconds of stats to be logged
sleep 30

dmesg -c | perl iodump

echo 0 > /proc/sys/vm/block_dump
/etc/init.d/klogd start

Thanks
Manoj