Sunday, April 28, 2013

Limit running Powershell script under specific path with AppLocker

Say if you have a management server or a script repository server, sometimes users save/test/run their script from different path, it is different to maintain the script version, and it is hard to determine which script can be removed or kept on the server.

here is a solution,  you can save all scripts in a central directory, and keep script from running in other path with Applocker. let's say my scripts are saved in c:\work:
1. Open "local security policy" by secpol.msc

2. Open "Security Settings" -> "Application Control Policy"->"Applocker"->"Script Rules"

3. Right click "Script Rules", Click "Create New Rule..."

4. Select "Allow", and enter the user name which

5. Select "Path"

6. Enter the script file path "C:\work"

7. Click "Next" if you don't need exception

8. Enter the Name of the Rule

9. Click "Yes" to create default rule if it is the first time you use Applocker

After the rule created, if you run powershell script from other path, for instance "c:\temp", you will get error

Only running powershell script under c:\work is allowed.

Actually no only powershell script, but also other script like(.com,.bat...) can only be run from c:\work,

you can create other rules to meet your requirement.

Wednesday, April 10, 2013

Set DAC port with a specific number

Usually named instance can uses dynamic port, if firewall setup on the server, you can use SQL Server Configuration Manager to assign a specific port to SQL Server instance. However, there is no UI to reconfigure the DAC port, you need to use regedit.exe to configure a specific port number.

1. Run regedit.exe
2. Open registry key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQLX.InstanceName\MSSQLServer\SuperSocketNetLib\AdminConnection\Tcp

"X" is the sql server version number, "InstanceName" is the sql server instance name. for instance, my sql2012 named instance is "SQL2012", the path is like below
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL11.SQL2012\MSSQLServer\SuperSocketNetLib\AdminConnection\Tcp

3. Set Value "TcpDynamicPorts" to a specific port number

here we set the  "TcpDynamicPorts" to 12345.

4. Restart sql server service, then in errorlog you can find the DAC is monitoring port 12345
2013-04-10 15:30:16.22 Server      Server is listening on [ ::1 <ipv6> 12345].
2013-04-10 15:30:16.22 Server      Server is listening on [ <ipv4> 12345].
2013-04-10 15:30:16.22 Server      Dedicated admin connection support was established for listening locally on port 12345.

5. Validate the connection with DAC
sqlcmd -S tcp:localhost,12345 -E

please note, don't need to use parameter -A in sqlcmd command line.

Friday, April 5, 2013

Use delegated session configuration in Powershell 3.0

Powershell 3.0 has many new feature, and they are useful in some circumstance.

let's say User A log in server A, and he wants to access the resource on Server B, however User A doesn't have permission to access the resource, User B has resource access permission, so User A needs to use User B's credential.

Normally if we want to use remote session to access resource , we can use cmdlets
1. Enter-PSSesssion
2. Invoke-Command.

However we need to provide User B's credential and password when create remote session. There is potential risk, sometimes we don't want to give the password to operators, in that case, we can use delegated session configuration.

Here is the step
1. Register a new session configuration with "-RunAsCredential UserB" on Server B

Register-PSSessionConfiguration -Name DomainAdmin -RunAsCredential xxx\administrator -ShowSecurityDescriptorUI

Here we create a session configuration named "DomainAdmin", and the session will be run as user "xxx\administrator" credential

2. Grant full access to User A
In the next popup window, grant full access to User A

3. Verify the session configuration
you can run "Get-PSSessionConfiguration" to view the all session configuration on Server B.
or you can run "Set-PSSessionConfiguration DomainAdmin -ShowSecurityDescriptorUI" to configure the permission.

4. Now on server A, create remote session with "-ConfigurationName" parameter
Enter-PSSession -ComputerName ServerB -Credential xxx\UserA -ConfigurationName DomainAdmin

here we use UserA's credential to create remote session, and use session configuration DomainAdmin. so we just need provide password for UserA when creating remote session, then we can run as User B's credential on Server B

so when we run whoami, it shows the current user is administrator(User B).

delegated session configuration is easy to use, and very useful especially on system maintenance work.

Wednesday, April 3, 2013

Compression Backup with BUFFERCOUNT parameter

If you want to make you backup faster, you can try BUFFERCOUNT parameter with compression backup.

From Book Online description:

BUFFERCOUNT = { buffercount | @buffercount_variable }
Specifies the total number of I/O buffers to be used for the backup operation. You can specify any positive integer; however, large numbers of buffers might cause "out of memory" errors because of inadequate virtual address space in the Sqlservr.exe process.
The total space used by the buffers is determined by: buffercount * maxtransfersize.

Below is my testing result, all backups use compression parameter. the data file is 195GB with 11GB used. by using compression, the backup file is 8.4GB

1. No BUFFERCOUNT parameter

it completed with 88MB/sec throughput, avg cpu% is 45

2. Add BUFFERCOUNT parameter
it completed with 105MB/sec throughput, avg cpu% is 50

Next I tried BUFFERCOUNT = 100, BUFFERCOUNT = 150 and BUFFERCOUNT = 200

here is the result:

based on the diagram upper, when BUFFERCOUNT = 100, Throughput reach the ceiling, comparing with the first command without BUFFERCOUNT parameter(default), we made the backup process 30% faster.

you can also use multiple backup files to reach the same goal. 

3. Test multiple backup files
my sql server has 2 CPU, so I use 2 backup files:
DISK = 'c:\temp\abc1.bak',
DISK = 'c:\temp\abc2.bak'

it completed with 115MB/sec throughput. avg cpu 60%.

4. Test multiple backup files with BUFFERCOUNT parameter
DISK = 'c:\temp\abc1.bak',
DISK = 'c:\temp\abc2.bak'

based on the diagram upper, there is only 5% performance difference between using BUFFERCOUNT and no BUFFERCOUNT.

Although BUFFERCOUNT makes higher CPU %, the backup always runs during off business, so if you can afford the higher CPU% penalty, it is worth to try BUFFERCOUNT. Please test the appropriate BUFFERCOUNT value based on your environment.