Where to start with power cli

Why use PowerCLI
 The biggest question to ask is:
 Why would I use PowerShell (PoSH) if there
is a perfectly good Graphical User Interface?
 When there is Administration of Multiple
systems there is always a need for
scripting.
 Basic Example:
○ Get a list of all VM, just by their names

Script and Output
Get-VM | select Name
Name
====
Server1
Server2
Server3
Server4
Server5
Server6
Server7
…

Real World Scenario
 Joe is an Administrator at a small Oil
and Gas company that has 4 ESXi
servers and 120 VMs running on them.
 Joe’s manager requests a report for a
list of Servers in the environment, with
the amount of CPUs, Memory, Disk
Space used.
 “Piece of Cake” Joe says as he goes to
the VIClient to pull a report from the
GUI.

Using the GUI
 Joe selects Inventory 
Hosts and Clusters,
Selects the vCenter host
and then selects the
“Virtual Machines” Tab.
 He sorts the Virtual
Machines by name and
examines what fields are
able to be displayed.

Shortcomings of Using the GUI
 Joe assesses that using the GUI can be
done but he knows his manager and he
will ask for this report again, and again,
and again, and he would like to either
automate this or have this running via a
single script.
 Joe also wants to exclude certain
servers as they are test machines and
are not needed for this report for his
manager. (Names Start with Test)

Attempting the first script
Needs:
Name, vCPUs, Memory and Disk Used
Script:
Get-VM | Select Name, NumCPU, MemoryGB,
UsedDiskGB

First Script Output
Output:
Name NumCPU MemoryGB UsedDiskGB
==== ====== ======== ==========
Server1 2 4.0000008 31.0103883
Server2 4 7.999293 48
TestServer1 1 1.9199201 48
 As you can see the script produced the
results we were looking for, however with
some mixed output results, and what about
the exclusion of Test machines.

First Script Revamp
Script:
Get-VM | Select Name, NumCPU,
@{Name=“Memory”;Expression={[System.Math]::Round(
$_.MemoryGB, 2)}}, UsedSpaceGB
Explanation:
 Okay, this looks complicated but when you break it down it is
very similar to the first attempt, but we are naming the
MemoryGB – “Memory” and using a system method using a
Math Function to Round the variable to 2 decimal points.
 We could also do this to the UsedSpaceGB to make it easier
to read.

First Script Revamp Output
Output:
Name NumCPU Memory UsedDiskGB
==== ====== ======== ==========
Server1 2 4 31.0103883
Server2 4 7.99 48
TestServer1 1 1.91 48
 As you can see the script produced the
results we were looking for, however with
some mixed output results, and what about
the exclusion of Test machines.

First Script Revamp (part 2)
Script:
Get-VM | where{$_.Name –notmatch “Test”} | Select
Name, NumCPU, @{Name=“Memory”; Expression=
{[System.Math]::Round($_.MemoryGB, 2)}},
@{Name=“Used Disk”; Expression=
{[int]$_.UsedSpaceGB}}
Explanation:
 We added two additional components to this one
 First to remove the VMs with the name Test within it.
 Second to format the usedSpaceGB to a number with no decimal places.

Script Revamp Output (2)
Output:
Name NumCPU Memory Used Disk
==== ====== ======== ==========
Server1 2 4 31
Server2 4 7.99 48
Notice the formatting is good
the test server is removed
balance to the force has been restored.

Now for Something Useful
 Who has to deal with aging snapshots
when other administrators in your group
think that a snapshot is a backup?
 Your datastores show a red exclamation
mark and seem to be almost full???
 Script:
The easiest would be to blanket remove all the
snapshots via this script
Get-VM | Get-Snapshot | Remove-Snapshot

Snapshot Script
 The problem with this is that it may take
DAYS to reconcile the snapshots and you
want to see how bad the damage is before
you run this.
 So you run a variation on the original script
to firstly produce a list and size of the
snapshots and secondly limit the scope of
reconciliation.
Get-VM | Get-Snapshot | Where {$_.SizeGB -lt 1 -and
$_.Created.Day -lt (Get-Date).Day}

Snapshot Script Output
Script:
Get-VM | Get-Snapshot | Where {$_.SizeGB -lt 1 -and
$_.Created.Day -lt (Get-Date).Day}
Output:
Name Description PowerState
---- ----------- ----------
Test PoweredOff
 Here is an example of the typical output from that
script. You can pull the information about the
Snapshot by adding a “| fl *” after it. This
displays all the information available (fl is an alias
for Format-List)

Where to go next
 I started by using Powershell.exe as my
main command line interpreter, instead of
cmd.exe.
 I also tried to use the command line
wherever possible to ensure memory of the
commands
 Document your findings!
 Maintain a script repository with specific
naming. Native commands use Get, New
and Set, consider using different verbs to
differentiate your scripts (Do, Put, or
Change)

Questions?
Where do YOU want to go next?
1 Liners Link
http://darusintegration.blogspot.ca/2011/11
/quick-and-easy-powershell-one-
liners.html

Where to start with power cli

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