Tech Bites

Blog of interesting data center technical tips / tasks / articles which we come across

How to replace text inplace without opening it, using sed

I have always loved range of text searching and editing tools in Linux. Be it grep to search for various patterns in a file. Or awk to print parts of a file in required format. Or the general purpose vi editor. Or the stream editor sed. Am writing this post to highlight just one feature…
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November 8, 2017 0

Scan newly added disks or rescan resized disk in Linux VM

How do we rescan for new disks after adding a VMDK to a Linux Virtual Machine? First, list all disks available in the VM sudo fdisk -l Running the following command will scan for new scsi disks. sudo echo “- – -” > /sys/class/scsi_host/host0/scan .. .. sudo echo “- – -” > /sys/class/scsi_host/hostN/scan Run this…
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November 1, 2017 0

PowerShell for Failover Clustering: CSV Free Disk Space

A one liner that gives the info we need regarding usage of the cluster shared volumes in Windows 2012 Get-ClusterSharedVolume | select -Expand SharedVolumeInfo | select -Expand Partition | ft -auto Name,@{ Label = “Size(GB)” ; Expression = { “{0:N2}” -f ($_.Size/1024/1024/1024) } },@{ Label =”FreeSpace(GB)” ; Expression = { “{0:N2}” -f ($_.FreeSpace/1024/1024/1024) } },@{…
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January 12, 2016 0

How to find architecture of a Linux OS (32 bit or 64 bit)

I have been using getconf to find architecture of a linux os (32 bit or 64 bit) for a quite some time. But today, I came to know that there are several other ways to check this too. This is what I have been using: [root@Enlit.me~]# getconf LONG_BIT 64   Other options are: [root@Enlit.me~]# arch…
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August 2, 2014 0

Add multiple Virtual Machines to Networker VADP backup

Instead of adding clients manually one at a time through the Networker Management Console GUI, you can perform an initial bulk import using cmd line interface: nsradmin -i import-file where the import-file contains many lines like this create type: NSR Client;name:win-vm;comment:SOME COMMENT;aliases:win-vm,win-vm.enlit.me;browse policy:Day;retention policy:Day;group:VM-Image-Daily;Proxy backup host:my-vcenter.enlit.me;Proxy backup type:VADP; Use excel to form a large csv,…
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May 14, 2014 1

SATA, SAS and NL-SAS disks

There are different kinds of hard drives: Serial Attached SCSI (SAS), Near Line SAS (NL-SAS), Serial ATA (SATA), Fiber channel (FC) and Solid State Drives (SSD). FC and SSD are fast and faster disks. Let’s see about the first three. So, what is the real difference between SAS, NL-SAS and SATA disks? SAS Of the…
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April 22, 2014 1

Tape Drive formats or standards

AIT (Advanced Intelligent Tape) AIT is 8mm across and uses helical scanning technique and the MIC (Memory In Cassette) technology to provide increased access. It also supports high data transfer rate up to 78 MB/sec and maximum storage capacity of 500GB compressed using ALDC (adaptive lossless data compression) technologies. DAT (Digital Audio Tape) DAT is…
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April 21, 2014 0

Troubleshooting Auto_ethX issues

With multiple NICs installed, udev would sometimes change order in which they were named. This leads to inconsistent network interface name between reboots. And NetworkManager also creates problems by renaming the interface to Auto_ethX. Ex: auto_eth0 Sometimes, we see that a device is continuously named wrongly or does not allow us to give a specific…
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April 14, 2014 0