Administering SQL Server 2008 with PowerShell : Step-By-Step Examples (part 2) - Common OS-Related Tasks

Common OS-Related Tasks

Now let’s look at some more OS-related tasks, while keeping our focus on SQL Server–related tasks.

Let’s check the status of the SQL Server service using the Get-Service cmdlet in the regular PowerShell console:

PS>Get-Service "mssqlserver"
Status   Name               DisplayName
------   ----               ------------
Stopped  MSSQLSERVER   SQL Server (MSSQLSERVER)
PS>

The service is stopped. When you use the pipeline feature of PowerShell, the service is started:

PS>Get-Service "mssqlserver"|Start-Service
WARNING: Waiting for service 'SQL Server (SQLSERVER)
  (MSSQLSERVER)' to finish starting...
WARNING: Waiting for service 'SQL Server (SQLSERVER)
  (MSSQLSERVER)' to finish starting...
PS>

This example demonstrates using the pipeline to chain commands together. Alternatively, you could use Start-Service directly:

PS>Start-Service "mssqlserver"

The difference between the two methods demonstrates some of the power in PowerShell. When you use Get-Service, a service object is retrieved. When you use the pipeline, this object is passed to Start-Service. Start-Service is built to basically accept input from the pipeline and autofills its parameters based on what was input; thus, it knows to start the SQL Server service.

Most administrators have probably already used the Windows Task Manager to look at the SQL Server processes. Perhaps it was to determine whether SQL seemed to be using too much memory or some other issue. PowerShell provides the Get-Process cmdlet, shown here, to look at running processes:

PS>Get-Process sqlservr
Handles  NPM(K)    PM(K)      WS(K) VM(M)   CPU(s)
  Id ProcessName
-------  ------    -----      ----- -----   ------
  -- ------------
    318      45    64156      44288  1554     2.03
  572 sqlservr
PS>

Another common OS-related task is to look for events in the Windows application event log:

PS>Get-EventLog Application -New 10
PS>Get-EventLog Application -New 10| `
  Where {$_.EntryType -eq "Error"}
PS>Get-EventLog Application -New 10| `
  Where {$_.EntryType -eq "Error"}|Select-Object TimeWritten

The preceding example demonstrates another useful feature of the PowerShell pipeline where you can join several commands together to get specific results. First, only the 10 newest entries are retrieved; then a pipe is used to get only the entries classified as an error, and finally, only the TimeWritten property is displayed.

WMI is packed full of features that are useful for system administration. A few examples of using PowerShell’s built-in WMI features are shown here.

• Getting a listing of all the fixed local logical drives:

  PS>Get-WmiObject -query "select * from Win32_LogicalDisk   where
  DriveType='3'"
  

• Getting a listing of all the fixed remote logical drives:

  PS>Get-WmiObject -computerName server -query
    "select * from Win32_LogicalDisk where DriveType='3'"
  

• Getting a listing of all the local patches/hotfixes installed (the –computerName parameter could be used with a value to retrieve this information from a remote system):

  PS>Get-WmiObject Win32_QuickFixEngineering
  

The preceding examples show only the beginning of all the things WMI can provide quick access to. Another common task is trying to find files or folders. You can use the Get-ChildItem cmdlet to recursively search through a directory structure. The following example shows how to search for the location of the powershell.exe executable:

PS>Get-ChildItem c:\ -recurse powershell.exe

SQL Server–Specific Tasks

Before jumping into more hardcore SQL Server PowerShell features, let’s briefly look at the SQL Server event log. Fortunately, the log simply contains text-based files, which PowerShell can read. You could use the Get-Content cmdlet to view the entire log, but instead you can use the Select-String cmdlet to look for a specific string or pattern in the error log file. First, you change the current location to the SQL Server log directory:

PS>Set-Location "C:\Program Files\Microsoft SQL Server"
PS>Set-Location (join-path $pwd "MSSQL10_50.MSSQLSERVER\MSSQL\Log")
PS>Select-String "error" ERRORLOG

The PowerShell prompt in the preceding example is simply a generic one because the preceding commands would work both in the default PowerShell console and in the SQL Server PowerShell minishell.

An example of taking this further would be to retrieve all the errors in the ERRORLOG file. When you use Get-Member and Format-List to look at the object output by Select-String, the date is hidden inside a string in the Line property:

PS >
Select-String "error" ERRORLOG|foreach{$_.line}|where{$_ -match "^20*"}|
foreach{$date,$time=$_.split()[0],$_.split()[1];[datetime]$($date+" "+$time) }
PS >


					  

The preceding example demonstrates how to look for the string "error" in the current SQL Server ERRORLOG file. For all the lines that match, the Line property is passed along the pipeline. Next, based on some testing, it appears that you want to search only lines that start with "20*-". From that object, two values are retrieved: $_.split()[0] and $_.split[1]. These values are placed in the $date and $time variables, respectively. From there, they are recombined, and a type accelerator is used to indicate that this is a date/time object, so any calculations against this value will be simplified. What is finally output is the time stamp showing when the error occurred.

Using the Provider

Using the SQL Server provider can be very handy in navigating the system. Starting PowerShell from SSMS, DBAs can easily find their way through different objects as if working with files and directories.

When the SSMS is used to start PowerShell at the server level, the databases are down one level, and from there tables and users, for example, can also be easily accessed.

In the session shown in Figure 1, we navigated to a particular database and entered a dir Tables command. The output from the last command would scroll beyond the current screen, so only the first part of the output is displayed.

Figure 1. Navigating the SQL Server provider.