Pawan’s Blog

A brief description of the steps which occurs in a simple SCCM OSD task sequence

PingPawan — Sun, 11 May 2014 23:34:00 GMT

Hello People,

In continuation to my last blog PXE Deep Dive, I am writing this one next in the series

Before the Task Sequence begins, there are series of steps which occur:

Once the PC boots into WinPE from Boot Media or PXE , the machine connects to the Management point to download the policies.

Point of failures at this stage are:-

MP communication
NIC and storage drivers

To verify if the drivers are correct or not, enable Command line support in the boot image.

Once winPE initializes, open Command prompt by pressing F8, type ipconfig.

If you see an IP address assigned to the machine, it can be concluded that PC has the correct NIC drivers.

Next type DISKPART in command prompt hit enter

Type List Disk

If you see the HDD listed there, your storage drivers are OK.

To verify MP communication, go through SMSTS log which is located at X:\windows\Temp\SMSTSLOG

In ConfigMgr 2012, you can directly open the log in WINPE as CMTRACE is included in WINPE and. Depending on the architecture of the boot image it is located under

X:\SMS\BIN\I386\cmtrace.exe or X:\SMS\BIN\x64\cmtrace.exe

Once we verify the above are working OK, assuming there are only optional deployments , we should be prompted with the list of task sequences available for that machine.

If the machine has a required task sequences deployment, it will start the task sequences execution.

The first thing the PC will do is to check the task sequences dependencies. i.e. it will verify the distribution point location for all the packages referenced in the task sequence.

Once it gets at least one Distribution point location for all the packages, then only it initiates the Task Sequence execution.

The first thing it does is, it creates a list of steps which it will perform in the entire execution

It does so by parsing the TS as shown in the screenshot

The above screenshot shows extract of the steps which the TSmanager will execute. Please notice that this is a truncated log and you may not see your log exactly the same way as you see here.

This log tracks the initial policy download and MP communication. Please note that the log is truncated and only shows the points of interest

Contd..

Following are the bare minimum steps which you would generally see the Task sequence to deploy an OS :-

Restart in WINPE

This step is required so that that actual WIM file can be laid down on to the hard drive. This step is only needed when the Task Sequence starts in the full OS and its purpose is to lay down WinPE on the hard drive so it can reboot into WinPE from the hard drive. WinPE is a mini OS for purposes of deploying Windows

Logs will always be under X:\Widows\Temp\SMSTSLog. They should ALWAYS be obtained from this location

This step does not run when booted from PXE or boot media due to a condition that is placed on it. The condition evaluates the variable SMSTSinWinPE to determine if it is FALSE. If in WinPE, SMSTSinWinPE will evaluate to TRUE. If not in WinPE, SMSTSinWinPE will evaluate to FALSE. Booting from PXE or boot media boots directly in to WinPE so SMSTSinWinPE will evaluate to TRUE, causing the step to be skipped.

Next is:-

Format and Partition Disk

In this step the HDD is formatted so that OS can be laid down.

The associated executable with this step is OSDDiskPart.exe

Below is the truncated log for Format and partition log.

This log is truncated and you may not see as is.

The disk is formatted per the settings configured at this step.

In this step, notice that by default from Win7 onwards OS’s it actually creates two partitions one which is 350MB in size and other which utilizes 100% of the remaining Hard drive. (You can always customize this as per your preference.)

The “System Reserved” partition is created so that it can contain the boot files on a separate partition than the Windows partition. This allows additional features such as Bitlocker, WinRE, and recovery tools to be used. Also, the above only applies to BIOS PCs. It does not apply to UEFI PCs which use a completely different partitioning scheme.

The command that runs in this step is:-

Set command line: "X:\windows\system32\diskpart.exe" /s "X:\windows\TEMP\DiskPartScript.txt

The text file is immediately deleted after the completion of this step.

Apply Operating System Image

Then drive is wiped excluding C:\_SMSTaskSequence, c:\SMSTSClientCache and %OSDStateStorePath%. Boot files are then copied to root of drive and BCD is written. It then finally saves the initial windows configuration to C:\windows\panther\unattend\unaddend.xml. The component which does all these is ApplyOperatingSystem.

Once the Disk is formatted, the next step is the Apply Operating System task. In this step, the wim file is copied to C:\_SMSTaskSequence\Packages if the download settings for package is "download and run".

The image is applied to the hard drive which basically copies all of the contents in the WIM file to the hard drive.

The image is applied by using wingapi.dll

Boot files are copied and the BCD is created on the boot partition and not necessarily the Windows partition. This goes back to the System Reserved partition which I clarified on in the Format and Partition Disk step. The System Reserved partition is the boot partition and this is where boot files are copied to and the BCD created.

It then finally saves the initial windows configuration to %Windir%\panther\unattend\unaddend.xml

The associated executable with this step is ApplyOperatingSystem.exe

Below is another truncated log while OS is getting applied :-

Points of interest are highlighted

Cont.…

Cont…

Apply Windows Settings/ Apply Network Settings :

In both these steps, the OS/network specific settings are added to the existing %windir%\panther\unattend.xml file.

The associated executables with these steps are OSDWinSettings.exe and OSDNetSettings.exe

In these two steps the settings are not actually applied to Windows but only added to the unattend.xml file. The settings are not actually applied until the Windows Setup runs during the Setup Windows and ConfigMgr task.

Apply Network settings:-

Apply Device Drivers:

In this step, the search is done on entire Drivers catalogue and a list of drivers is prepared which will be installed once the Full OS boots.

The associated executable with this step is OSDDriverClient.exe.

In the above case, the PC was a virtual machine hence no drivers were installed.

Setup Windows And Configmgr:

The Client installation files are copied to C:\_SMSTaskSequence\Packages. The boot manager is updated to boot into the Windows OS installed at the Apply Operating System task and the machine is rebooted to full blown OS and windows setup is run. In this phase windows and network settings, are actually executed using the unattend.xml file which was created earlier.

Before booting out of WinPE and into the full OS, this task creates a SetupComplete.cmd file in the Windows installation under Windows\Setup\Scripts. In this file it adds the following line

%windir%\system32\osdsetuphook.exe /execute

SetupComplete.cmd is a Windows Setup file that gets executed once Windows Setup completes. In this way, the Task Sequence continues once Windows Setup is complete.

Once the task sequence continues, the ConfigMgr client install is completed, if there are additional steps, the task sequence will execute them. e.g. install application, apply software updates.

SMSTS log at this stage moves to C:\_smsTaskSequence. And after the client gets installed , it moves to C:\windows\ccm\logs

If everything goes as expected, the C:\_smstaskSequence folder is deleted and You will have the Operating system ready to use.

Deep Dive PXE boot flow for SCCM 2007/2012

PingPawan — Sun, 12 Jan 2014 01:06:00 GMT

Deep Dive PXE boot flow for SCCM 2007/2012

Hello All,

I have seen many people do not have their concepts clear about OSD PXE for SCCM. Hence I thought if writing this blog and I tried to elaborate as much as I can on this topic.

Machine does a network boot, it sends a broadcast to entire network with option 60. Both DHCP and WDS/PXE server gets the broadcast. DHCP offers the IP address to the client. But before the client machine requests for the offered IP, it waits for a green signal from WDS. WDS/PXE sever runs a stored procedure, LOOKUPDEVICE for the client machine against SCCM DB. If the machine is found in the DB or If there is an advert for Unknown collection, WDS signals client to proceed with the PXE boot.

Client machine now requests for the IP offered by DHCP and DHCP then acknowledges this IP assignment. Machine finally has an IP address and is ready to proceed further. (DORA completes).

Please Note

The above scenario is only true if we have the client machine PXE and DHCP all are in same subnet. If any of these 3 are in a separate subnet, necessary arrangement needs to be made so that the Broadcast sent by client could reach to both DHCP and PXE server.

Preferably, we configure IP helpers on the routers so that the broadcast can be forwarded to the DHCP and PXE server in the other subnet. One of the caveats here is if there are any king of security/firewall on the router/switches, proper arrangement needs to be made to allow the traffic.

For instance if DHCP snooping is used, the same needs to be allowed on the router/switches on the network as they potentially block the network traffic in these cases.

Now after the client machine gets an IP address, It downloads WDSNBP.COM from PXE server.

This file detects the hardware architecture on the machine and this information is later used at the time of boot image download.

Points of failure till this point:-

Client Machine may not be part of SCCM DB and there is not advert on Unknown collection. This can be tracked in SMSPXE.LOG which is available on PXE service point in MP directory.
Client machine is not in the same subnet as of the PXE and DHCP server. In this situation if the IP helper table is not configured, the broadcast sent by client will not be forwarded to the other subnet.
Ports: 66, 67 and 4011 should be open for IP assignment and WDS file download.

Let’s now look at the logs snippet from SMSPXE.

Screenshot from A failed machine and corresponding logs from SMSPXE

Client lookup reply:

00:15:5D:0B:02:4F, D4EE23C0-E33F-4AD1-8C11-17058ABE0C4E: device is in the database. SMSPXE 1/12/2014 11:13:13 AM 3156 (0x0C54)

Client boot action reply:

00:15:5D:0B:02:4F, D4EE23C0-E33F-4AD1-8C11-17058ABE0C4E: no advertisements found

00:15:5D:0B:02:4F, D4EE23C0-E33F-4AD1-8C11-17058ABE0C4E: No boot action. Aborted.

00:15:5D:0B:02:4F, D4EE23C0-E33F-4AD1-8C11-17058ABE0C4E: Not serviced. SMSPXE 1/12/2014 11:13:14 AM 3156 (0x0C54)

Client boot action reply:

SMSPXE 1/12/2014 11:13:17 AM 3156 (0x0C54)

00:15:5D:0B:02:4F, D4EE23C0-E33F-4AD1-8C11-17058ABE0C4E: no advertisements found SMSPXE 1/12/2014 11:13:17 AM 3156 (0x0C54)

================================================================================================================================

Screenshot from a successful PXE boot and corresponding SMSPXE log…

Client lookup reply:

SMSPXE 1/12/2014 11:23:51 AM 3156 (0x0C54)

00:15:5D:0B:02:64, 773FBA8A-EB14-453C-9EB1-B8F4657199BD: device is not in the database. SMSPXE 1/12/2014 11:23:51 AM 3156 (0x0C54)

Getting boot action for unknown machine: item key: 2046820352 SMSPXE 1/12/2014 11:23:51 AM 3156 (0x0C54)

Client boot action reply: 87776601-61c0-45d4-8425-363cf7803315

SMSPXE 1/12/2014 11:23:51 AM 3156 (0x0C54)

00:15:5D:0B:02:64, 773FBA8A-EB14-453C-9EB1-B8F4657199BD: found optional advertisement BLR20000 SMSPXE 1/12/2014 11:23:51 AM 3156 (0x0C54)

Getting boot action for unknown machine: item key: 2046820353 SMSPXE 1/12/2014 11:23:59 AM 3156 (0x0C54)

Client boot action reply: 304cce6c-b4ec-46fc-9f28-98c017b854f8

SMSPXE 1/12/2014 11:23:59 AM 3156 (0x0C54)

00:15:5D:0B:02:64, 773FBA8A-EB14-453C-9EB1-B8F4657199BD: found optional advertisement BLR20000 SMSPXE 1/12/2014 11:23:59 AM 3156 (0x0C54)

Looking for bootImage CAS00005 SMSPXE 1/12/2014 11:23:59 AM 3156 (0x0C54)

==============================================================================================================================================================================

So once client machine architecture detection is completed using WDSNBP.com, it proceeds further with the PXE boot. And it downloads the PXE boot files from PXE server. Depending upon the advertisement Client machine download the PXE boot files. The file downloaded at this step is controlled/ monitored by SMSPXE. SMSPXE runs a stored procedure called getbootaction and depending on the result, it gives the PXE boot files to client.

For Optional advertisement: PXE.COM (User to press F12 to continue with the Network boot)

For Mandatory Adverts: PXEBOOT.n12

If for any reason PXE boot has to aborted, machine downloads abortpxe.com. Possible reasons for aborting PXE boot could be machine is not allowed for PXE boot, Client has already done the PXE boot once and PXE boot flag is set to yes. No advert found for machine in DB. Etc…

The client machine now downloads the Boot image, bootmgr.exe and BCD store. BootMGR and BCD store are used to initialize the WINPE environment. Boot image downloaded here would be dependent on the result of the architecture detection done earlier by WDSNBP file.

Once the Boot image and the other two files are downloaded completely, it initializes the WINPE which in itself is a mini OS.

NOTE:

I have seen a couple of instances where the boot image download fails and you would see the Generic OS boot failure error message. Please do troubleshoot that error message as it is irrelevant to PXE boot. It just means that there is no OS found on the machine.

Once WINPE initializes, it does a DORA again and attain an IP address from DHCP server. In 99% cases the IP address is same as of the initial IP address. What’s important to know here is machine retries for the IP address and it’s not the one which it had originally while PXE booting

Once machine attains the IP address it finds the MP from AD and then connects to MP to download all the policies. And it gets all the policies are downloaded, user will be presented with the option to select the Task sequence. (If machine only has optional adverts)

Possible Failures at this stage:-

Machine reboots the moment WINPE screen appears.

Enable command prompt in WINPE and open CMD by hitting F8 once WinPE initializes. Make sure machine has an IP address and the HDD is getting detected. Command which you can run here is IPCONFIG and DISKPART. DISKPART will confirm the presence of storage while ipconfig will confirm network connectivity.

Chances are there that even though these two tests succeeds, the machine still reboots after winPE initialization.

Check if machine is able to find the MP and if yes if the communication is happening OK with MP or not.

Collect SMSTS log to see the detailed error and troubleshoot accordingly.

SMSTS log at this phase will be found at

X:\SMSTSLOG\SMSTS.lOG

X:\WINDOWS\TEMP\SMSTSLOG\SMSTS.LOG

Once you see the TS execution has started, we conclude PXE boot is working …

I will cover the TS execution steps in details in my upcoming blog!!!