Windows Server 2008 DHCPv6 Stateless and Stateful Mode

Windows Server® 2008 supports stateless and stateful DHCPv6 server functionality. DHCPv6 stateless mode clients use DHCPv6 to obtain network configuration parameters other than the IPv6 address, such as DNS server addresses. Clients configure an IPv6 address through a non-DHCPv6 based mechanism such as IPv6 address auto-configuration (based on the IPv6 prefixes included in router advertisements), or static IP address configuration.

In DHCPv6 stateful mode, clients acquire both the IPv6 address as well as other network configuration parameters through DHCPv6.

Reference: http://technet.microsoft.com/en-us/library/cc753493.aspx

Fix “could not locate entry in sysdatabases” Error

Problem: I ran into this error when executing a script on a SQL database.  I could attach or deattach the database, and SQL Management Studio showed the database was fine.

Fix: it turns out the database has ‘-‘ in the name, e.g. database_2008-10-01.  Renaming the database by removing ‘-‘ fixed the problem.

Do not use ‘-‘ in SQL database name.

Cannot Add User Account in Windows 7 Home Premium

Local Users and Groups management console (MMC) is not available in Windows 7 Starter and Home Premium.  Adding use account in these versions is through Control Panel / User Account.  If you get an error “The specified account is not valid, because account names cannot contain the following character…. Please type a different name”,

Here is how to troubleshoot

1. Verify the user account name do not contain the listing characters.
2. This error also happens when the user account name already exists.  Because the disabled account is hidden from Control Panel / User Account, type “net user” in the command prompt to view all user accounts.

Hide User Account in Windows 7 Logon Screen

One way to hide user account in Windows 7 logon screen is to disable the account if it is no longer in use.  This is probably the easiest way.

User account management usually is in Local Users and Groups management console (MMC).  For Windows 7 Professional and Enterprise Edition, user account can be disabled there.  However Local Users and Group MMC is not available in Windows 7 Starter and Home Premium Edition.  But it can be done through “net user” in the command line.

1. Launch Command Prompt as administrator.
2. Enter “net user” to list all the local user account.
3. Enter “net user <user name> /active:no” to disable the account.
4. Once the account is disabled, it is hidden from the logon screen and Control Panel/User Accounts.
5. To reactivate the account, enter “net user <user name> /active:yes”.

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Exchange Server 2010 Migration Articles

Some articles about Exchange Server 2010 Migration

• Migrating from Exchange Server 2003 to Exchange Server 2010: A Small Organization Perspective
• Real-World Exchange Server 2010 Migration: Preparing for the Move

SQL Server Authentication and Authorization

Just read a blog post illustrating the SQL account problem when moving or restoring SQL database between servers.  As the blog says:

“SQL Server security is a little complex, but for our purposes it’s enough to consider two core artifacts: logins and users. Logins are instance-level objects (stored in master) and users are database-level objects (stored in the user database). Each of these are responsible for authorization in their respective domains, i.e., used to grant permissions at the instance and at the database respectively. But only logins are used for authentication. So in order to even log on to the server you have to have a login.

Users and logins are associated with each other through a matching identifier called a SID, and in order for a person to connect to and use a database, he must have a user in the target database and matching login on the instance. And here’s where our problem comes from: while users are stored in and move with the database, logins are not and do not. They’re left behind:

The result of this is that someone who could connect to D when it lived on S may no longer be able to do so when it moves to T because their login is missing. This is reparable, of course: you just need to manually add the required logins to the new instance. It’s also not easily automatable, since the target instance may already have a different login with the same name, which would cause a collision.”

It sounds the Contained Database in the next version of SQL Server “Denali” solved the authentication problem.  For now, we can resync the user login by using

sp_change_users_login 'update_one', 'username', 'username'