How to Change the Pool Master

xe pool-emergency-transition-to-master

xe pool-designate-new-master host-uuid=

cat /etc/xensource/pool.conf

How to unhide a VM in XenServer?

To find the UUID of the hidden VM, type the following xe command:

xe vm-list

Make note of the UUID of the hidden VM.

b. To unhide the VM, type the following xe command:

xe vm-param-clear param-name=other-config uuid=<vm uuid> 

How to Set Locales (i18n) On a Linux or Unix

/etc/sysconfig/i18n

The /etc/sysconfig/i18n file sets the default language, any supported languages, and the default system font. For example:

LANG="en_US.UTF-8" 
SUPPORTED="en_US.UTF-8:en_US:en" 
SYSFONT="latarcyrheb-sun16"

How to Increase the size of CentOS 7 LVM by expanding the virtual machine disk

1. Identifying the partition type

As this method focuses on working with LVM, we will first confirm that our partition type is actually Linux LVM by running the below command.

fdisk -l

2. Increasing the virtual hard disk

3. Partition the new disk space

As outlined in my previous images the disk in my example that I am working with is /dev/sda, so we use fdisk to create a new primary partition to make use of the new expanded disk space. Note that we do not have 4 primary partitions already in place, making this method possible.

fdisk /dev/sda

We are now using fdisk to create a new partition, the inputs I have entered in are shown below in bold. Note that you can press ‘m’ to get a full listing of the fdisk commands.

‘n’ was selected for adding a new partition.

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): n

‘p’ is then selected as we are making a primary partition.

Command action
   l   logical (5 or over)
   p   primary partition (1-4)
p

As I already have /dev/sda1 and /dev/sda2 as shown in previous images, I have gone with using ‘3’ for this new partition which will be created as /dev/sda3

Partition number (1-4): 3

We just press enter twice above as by default the first and last cylinders of the unallocated space should be correct. After this the partition is then ready.

First cylinder (2611-3916, default 2611): "enter"
Using default value 2611
Last cylinder, +cylinders or +size{K,M,G} (2611-3916, default 3916): "enter"
Using default value 3916

‘t’ is selected to change to a partition’s system ID, in this case we change to ‘3’ which is the one we just created.

Command (m for help): t
Partition number (1-5): 3

The hex code ‘8e’ was entered as this is the code for a Linux LVM which is what we want this partition to be, as we will be joining it with the original /dev/sda5 Linux LVM.

Hex code (type L to list codes): 8e
Changed system type of partition 3 to 8e (Linux LVM)

‘w’ is used to write the table to disk and exit, basically all the changes that have been done will be saved and then you will be exited from fdisk.

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

You will see a warning which basically means in order to use the new table with the changes a system reboot is required. If you can not see the new partition using “fdisk -l” you may be able to run “partprobe -s” to rescan the partitions. In my test I did not require either of those things at this stage (I do a reboot later on), straight after pressing ‘w’ in fdisk I was able to see the new /dev/sda3 partition of my 10gb of space as displayed in the below image.

For CentOS/RHEL run a “partx -a /dev/sda3” to avoid rebooting later on.

That’s all for partitioning, we now have a new partition which is making use of the previously unallocated disk space from the increase in VMware.

4. Increasing the logical volume

We use the pvcreate command which creates a physical volume for later use by the logical volume manager (LVM). In this case the physical volume will be our new /dev/sda3 partition.

root@Mega:~# pvcreate /dev/sda3
  Device /dev/sda3 not found (or ignored by filtering).

In order to get around this you can either reboot, or use partprobe/partx as previously mentioned to avoid a reboot, as in this instance the disk does not appear to be there correctly despite showing in “fdisk -l”. After a reboot or partprobe/partx use the same command which will succeed.

root@Mega:~# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created

Next we need to confirm the name of the current volume group using the vgdisplay command. The name will vary depending on your setup, for me it is the name of my test server. vgdisplay provides lots of information on the volume group, I have only shown the name and the current size of it for this example.

root@Mega:~# vgdisplay
  --- Volume group ---
  VG Name               Mega
...
VG Size               19.76 GiB

Now we extend the ‘Mega’ volume group by adding in the physical volume of /dev/sda3 which we created using the pvcreate command earlier.

root@Mega:~# vgextend Mega /dev/sda3
  Volume group "Mega" successfully extended

Using the pvscan command we scan all disks for physical volumes, this should confirm the original /dev/sda5 partition and the newly created physical volume /dev/sda3

root@Mega:~# pvscan
  PV /dev/sda5   VG Mega   lvm2 [19.76 GiB / 0    free]
  PV /dev/sda3   VG Mega   lvm2 [10.00 GiB / 10.00 GiB free]
  Total: 2 [29.75 GiB] / in use: 2 [29.75 GiB] / in no VG: 0 [0   ]

Next we need to increase the logical volume (rather than the physical volume) which basically means we will be taking our original logical volume and extending it over our new partition/physical volume of /dev/sda3.

Firstly confirm the name of the logical volume using lvdisplay. This name will vary depending on your setup.

root@Mega:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/Mega/root

The logical volume is then extended using the lvextend command.

root@Mega:~# lvextend /dev/Mega/root /dev/sda3
  Extending logical volume root to 28.90 GiB
  Logical volume root successfully resized

There is then one final step which is to resize the file system so that it can take advantage of this additional space, this is done using the resize2fs command for ext based file systems. Note that this may take some time to complete, it took about 30 seconds for my additional space.

root@Mega:~# resize2fs /dev/Mega/root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/Mega/root is mounted on /; on-line resizing required
old desc_blocks = 2, new_desc_blocks = 2
Performing an on-line resize of /dev/Mega/root to 7576576 (4k) blocks.
The filesystem on /dev/Mega/root is now 7576576 blocks long.

Alternatively if you’re running the XFS file system (default as of RedHat/CentOS 7) you can grow the file system with “xfs_growfs /dev/Mega/root”.

With this method we have increased the virtual disk drive through VMware, created a new partition out of this newly unallocated space within the guest OS, turned it into a physical volume, extended the volume group, and then finally extended the original logical volume over the newer physical volume resulting in overall disk space being increased successfully.

https://youtu.be/KW1ScgdCIfs

CentOS 7 minimal Network configuration

#nmtui

#systemctl restart network

#ip addr

Amazon to Launch Cloud Data Center in Korea

Amazon’s announcement, which the company’s chief cloud evangelist Jeff Barr made in a blog post Wednesday, is yet another example of US-based cloud giants going aggressively after Asia’s rapidly growing cloud services market.
Other recent examples are IBM’s deal with Chinese data center provider 21Vianet to provide its Bluemix Platform-as-a-Service to customers in China and the launch of IBM’s first SoftLayer data center in India. Microsoft launched three cloud data centers in India earlier this year.
Asian cloud service providers are expanding data center capacity in the region too. Chinese e-commerce and cloud giant Alibaba recently brought online a new data center in the Zhejiang Province.
Barr listed existing Korean customers that will be able to take advantage of Amazon’s new cloud data center capacity when it comes online. They include startups, gaming companies, and enterprises, the latter category including the electronics giant Samsung.
“These customers (and many others) have asked us for a local region,” Barr wrote. “We are looking forward to making it available to them and to many other enterprises, startups, partners, government agencies, and educators in Korea.”

http://www.datacenterknowledge.com/archives/2015/11/05/amazon-to-launch-cloud-data-center-in-korea/

Amazon brings Microsoft users into AWS with Active Directory service

Amazon has launched an AWS Directory Service for Active Directory, a fully managed implementation of Microsoft's authentication and user management service.

Using Active Directory in Amazon's cloud will enable companies to bring applications including SQL Server, SharePoint and custom applications built with .NET onto AWS. That's useful for businesses trying to move into the cloud from an on-premises deployment of Microsoft's software. 

When companies start using the service, it creates a pair of domain controllers connected to a user's virtual private cloud running Windows Server 2012 R2. Each domain controller runs in a different availability zone of a user's choosing inside a single region, and Amazon will handle the nuts-and-bolts of managing things like host monitoring, data replication and snapshots.

Administrators will be able to configure a trust relationship between their on-premises Active Directory and the AD in Amazon's cloud, so that users can sign in to both systems using one login. 

Companies can try the service for free for one month or 750 hours, whichever comes first. After that, the service costs US$0.40 per hour. 

It's an interesting move for Amazon, since one of the key products Microsoft uses to push its cloud services into large enterprises is Azure Active Directory -- a fully managed, cloud-based implementation of Microsoft's authentication and user management service with a whole bunch of other services and integrations baked in. It's an easy way to get one part of a business into Azure, which Microsoft can then use to try and upsell companies on other cloud services. 

How Amazon plans to expand this service to better compete against Azure AD remains to be seen, especially as it continues to fight with Microsoft to pursue dominance in the public cloud market.