AWS Notes

Elastic Load Balancing Deep Dive and Best Practices: https://www.youtube.com/watch?v=K-YFw9-_NPE

Redhat Tech Exchange 2015

Due to the recent tragic events last week in Bangkok, the RHTE organization is doing an effort to relocate the event out of Bangkok and Thailand to ensure your safety. While we have continuously monitored the news and travel advisories from various sources, we decided that the situation at this moment is not stable enough to proceed with the current locations.

Please allow us some time to rearrange the location and work on the logistics. In case of any questions please contact the staff atrhte@circusmax.com for more information. For now, please suspend all travel planning until you recieve a confirmation message with the new location and additional instructions.

more info @ http://redhat.events/rhte/

update: event was relocated to Ho Chi Minh City Vietnam

DevOpsDays Singapore

Reserve your ticket @ http://www.devopsdays.org/events/2015-singapore/registration/

Linux RAID Devices

To list disk

parted -l |grep sd #sd-scsi disks

Use in command line

parted parted /dev/sdb print

Creating a raid5

mdadm -Cv /dev/md0 --level=5 -n3 /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm --detail /dev/md0

Use the command below to create a copy of the partition of an existing disk then format then use mdadm --add to the array.

sfdisk -d /dev/ |sfdisk /dev/ Example: sfdisk -d /dev/sda | sfdisk /dev/sdb

Fail a disk

mdadm /dev/md0 -f /dev/sdb1

Remove a disk

mdadm /dev/md0 -r /dev/sdb1

Add a disk

mdadm /dev/md0 -a /dev/sdb1

Stopping md

mdadm --stop /dev/md0 

Start md

mdadm --assemble --scan

Saving mdadm config

echo 'DEVICE /dev/sd*' > /etc/mdadm.conf mdadm --detail --scan >> /etc/mdadm.conf

Removing array

mdadm -S /dev/md0 >> stop md mdadm --zero-superblock /dev/sdb1 mdadm --zero-superblock /dev/sdc1

Creating RAID 0

mdadm -Cv /dev/md0 --level=0 -n2 /dev/sdb1 /dev/sdc1

Creating RAID 1

mdadm -Cv /dev/md0 --level=1 -n2 /dev/sdb1 /dev/sdc1

Creating RAID 5

mdadm -Cv /dev/md0 --level=5 -n3 /dev/sdb1 /dev/sdc1 /dev/sdd1 --spare-disk=1 /dev/sde1 

 

 

Enable Wifi Dongle in Raspberrypi OSMC

Go to the command line interface of OSMC. Click the Power Icon. Select Exit, wait for the OSMC logo then press ESC.
Use username: osmc password: osmc

 Run the following Command:

 connmanctl  
 technologies  
 enable wifi  
 scan wifi  
 agent on  
 services  
 connect wifi_xxxxx #it will be a long string, hit tab for completion  

ref: https://osmc.tv/help/wiki/console
      https://discourse.osmc.tv/t/enable-wifi-under-gui/430/6

How to get the last IP address on the Subnet using Ruby

 >> require 'ipaddr'  
 >> ip=IPAddr.new("192.168.1.0/24")  
 => #<IPAddr: IPv4:192.168.1.0/255.255.255.0>  
 >> gateway=IPAddr.new(ip.to_range.last.to_i-1,ip.family).to_s  
 => "192.168.1.254"  
 >> ip=IPAddr.new("192.168.1.0/20")  
 => #<IPAddr: IPv4:192.168.0.0/255.255.240.0>  
 >> gateway=IPAddr.new(ip.to_range.last.to_i-1,ip.family).to_s  
 => "192.168.15.254"  

KVM Commands

To install with prompt

 virt-install --prompt  

List virtual machine

 virsh list 

Stop virtual machine

 virsh destroy

Configure VM autostart

 virsh autostart

Unconfigure VM autostart

 virsh autostart --disable

To install using kickstart

 virt-install --name=rhel03.localdomain -r 768 --disk path=/var/lib/libvirt/images/rhel03.localdomain.img,size=8 -l http://192.168.122.1/pub/inst -x "ks=http://192.168.122.1/pub/ks/rhel03.cfg"

To create VM snapshot

 virsh save centos01 centos01.snap.$(date +%y%m%d)

To restore VM snapshot

 virsh shutdown centos01  
 virsh restore centos01.snap  

Clone vm

 virt-clone --original centos01 --name centos02 --file /home/penoycentral/images/centos02.img  

Troubleshooting KVM

Error when starting the VM snapshot
error restoring domain unable to read from monitor


To fix

 virsh managedsave-remove domain-name