Install Hadoop Multinode Cluster using CDH4 in RHEL/CentOS 6.5

I have published my Article on this at tecmint.com

http://www.tecmint.com/install-hadoop-multinode-cluster-in-centos/

 

How To Fix Status 7 Error with CWM Recovery on Rooted Android!

I was installing Cynogen 10.2(and many other custom ROMs) on samsung galaxy ace plus and got very frustrating error with Status 7. google'ed it and found below video which is awesome and helped me :)


http://www.youtube.com/watch?v=QW1znjDLe-k

Best android apps 2014

• android device mgr
• cal
• pixlr express
• startup mgr
• flesky
• feedly
• cleaner master
• mx player
• big oven
• sketch book mobile
• assistance
• duolingo
• toucher pro
• trubackup
• themer
• applock
• 500 firepapers
• the android cop
• cpu-z

And my host got up :)

This is not any knowledge sharing post but one amazing experience that I should never forget and would like to share with you so that in future if you stuck like me this can help you :)

Sunday Afternoon (16 Feb 2014 ). Yes I work on weekends too :( I was working on some database maintenance activity and wanted to install one of the package on XYZ linux server. I typed rpm -qa command to check something and suddenly got an error “Connection refused” ! Nagios started shouting that server is down !!  Then I logged into our vm stack and found that kernel crashed because of corrupt/missing C libraries..now no option, tried maintenance mode but no luck :(  Only one option was left – boot that vm using live centos image, find existing file system and see if you can correct it.. from where to get live centos DVD ? I searched in entire storage volume and got one :) Booted VM using DVD in rescue mode and found corrupt file. Now how to correct it? I knew that server ABC is centos 5.5 tried copied file from it, matched md5sum and voila!! Server got up! J

MegaCli Commands

Adapter parameter -aN
The parameter -aN (where N is a number starting with zero or the string ALL) specifies the PERC5/i adapter ID. If you have only one controller it’s safe to use ALL instead of a specific ID, but you’re encouraged to use the ID for everything that makes changes to your RAID configuration.

Physical drive parameter -PhysDrv [E:S]
For commands that operate on one or more pysical drives, the -PhysDrv [E:S] parameter is used, where E is the enclosure device ID in which the drive resides and S the slot number (starting with zero). You can get the enclosure device ID using "MegaCli -EncInfo -aALL". The E:S syntax is also used for specifying the physical drives when creating a new RAID virtual drive.

Virtual drive parameter -Lx
The parameter -Lx is used for specifying the virtual drive (where x is a number starting with zero or the string all).

Controller information

MegaCli -AdpAllInfo -aALL
MegaCli -CfgDsply -aALL
MegaCli -AdpEventLog -GetEvents -f events.log -aALL && cat events.log

Enclosure information

MegaCli -EncInfo -aALL

Virtual drive information

MegaCli -LDInfo -Lall -aALL

Physical drive information

MegaCli -PDList -aALL
MegaCli -PDInfo -PhysDrv [E:S] -aALL

Battery backup information

MegaCli -AdpBbuCmd -aALL

Controller management

Silence active alarm

MegaCli -AdpSetProp AlarmSilence -aALL

Disable alarm

MegaCli -AdpSetProp AlarmDsbl -aALL

Enable alarm

MegaCli -AdpSetProp AlarmEnbl -aALL

Physical drive management


Set state to offline

MegaCli -PDOffline -PhysDrv [E:S] -aN

Set state to online

MegaCli -PDOnline -PhysDrv [E:S] -aN

Mark as missing

MegaCli -PDMarkMissing -PhysDrv [E:S] -aN

Prepare for removal

MegaCli -PdPrpRmv -PhysDrv [E:S] -aN

Replace missing drive

MegaCli -PdReplaceMissing -PhysDrv [E:S] -ArrayN -rowN -aN

The number N of the array parameter is the Span Reference you get using "MegaCli -CfgDsply -aALL" and the number N of the row parameter is the Physical Disk in that span or array starting with zero (it’s not the physical disk’s slot!).

Rebuild drive

MegaCli -PDRbld -Start -PhysDrv [E:S] -aN
MegaCli -PDRbld -Stop -PhysDrv [E:S] -aN
MegaCli -PDRbld -ShowProg -PhysDrv [E:S] -aN

Clear drive

MegaCli -PDClear -Start -PhysDrv [E:S] -aN
MegaCli -PDClear -Stop -PhysDrv [E:S] -aN
MegaCli -PDClear -ShowProg -PhysDrv [E:S] -aN

Bad to good (or back to good as I like to call it)

MegaCli -PDMakeGood -PhysDrv[E:S] -aN

This changes drive in state Unconfigured-Bad to Unconfigured-Good.

Walkthrough: Change/replace a drive

Set the drive offline, if it is not already offline due to an error

MegaCli -PDOffline -PhysDrv [E:S] -aN

Mark the drive as missing

MegaCli -PDMarkMissing -PhysDrv [E:S] -aN

Prepare drive for removal

MegaCli -PDPrpRmv -PhysDrv [E:S] -aN

Change/replace the drive

If you’re using hot spares then the replaced drive should become your new hot spare drive:

MegaCli -PDHSP -Set -PhysDrv [E:S] -aN

In case you’re not working with hot spares, you must re-add the new drive to your RAID virtual drive and start the rebuilding

MegaCli -PdReplaceMissing -PhysDrv [E:S] -ArrayN -rowN -aN
MegaCli -PDRbld -Start -PhysDrv [E:S] -aN

How to setup passwordless ssh - linux

Tired of typing passwords every time ? then you might want to check below method :)
  
In this tutorial I will guide you regarding how to setup passwordless ssh (key based ssh) between two linux hosts.

I have 2 VMs and I would like to setup key based ssh from ansible-ground (first VM) to qabox (second VM) as root user.

Steps :

1. Generate ssh key pair on host A i.e. ansible-ground in my case.

ssh-keygen -t rsa

2. Copy public key generated in above step to host B i.e. qabox in my case.

ssh-copy-id -i ~/.ssh/id_rsa.pub root@qabox

Note : root is the username for which you need password less ssh and qabox is host B


3. On host B - set the correct permissions for copied public key.

chmod 0600 ~/.ssh/authorized_keys


4. We are done!  now try to login from A-->B with root user.


Please let me know in case of issues.

Install Apps, Transfer music to/from your iPhone without iTunes !

iOS (previously iPhone OS) is a mobile operating system developed and distributed by Apple Inc. Unlike computer operating system, iOS places each app (including its preferences and data) in a sandbox at install time for security reasons. So most of users don't care about the iOS file system since they don't have an access.
However, some software developers brought several options that allow you to browse and explore the iPhone iPad iOS file system just like viewing files in Windows Explorer. And iFunbox is one of my favorite.

iFunbox Classic Window

Although iFunbox is primarily preferred by senior iPhone users, this is an easy-to-use and intuitive app. In iFunbox Classic window, you can browse and transfer User Applications, manage App file sharing, explore general storage, cameras, ibooks, voice memos, etc.

iFunbox Managing App Data Window

On iFunbox Managing App Data window, all your apps are listed there. Double click one of them and you'll see its inner file structure.



As an alternative to iTunes, iFunbox allows you to copy and move files within iTunes File Sharing supported apps so you won't get confused about Apple ID or other iTunes limits any more.
But an interesting paradox is that both iTunes File Sharing and iFunbox require internet connection so you have to make sure the network is working when using iFunbox.

iFunbox Quick Toolbox

iFunbox Quick toolbox provide several interesting quick shortcuts, such as import music to iPhone, transfer iPhone photos to computer, etc. I don't recommend to use iFunbox to transfer iPod music or iPhone photos because there is no option to choose which song or picture do you want to export.

For example, if you want to transfer a few songs from iPhone to computer, you can only select the whole library by default instead of picking up particular ones to move. For a professional iPhone Music Transfer software, I highly recommend you "PhoneTrans".



Stay connected for more ;-)