DOS command-line tricks

Remember DOS? It's still with us, in the form of the Windows command prompt, and it still has some useful tricks up its sleeve. I recently needed to automate the daily copying of some database backup files from one server to another. I combined several DOS, Windows and Windows task schedule techniques to make this work.

The goal: At 7:30 AM each day, copy all files named ynot_backup_*.bak from the folder G:\sqlbackup on the database server to the folder G:\ynot_backup on one of the web servers. Both servers are running Windows Server 2003.

First, I came up with an xcopy command to copy the appropriate files: xcopy /Y g:\SQLBackup\ynot_backup_*.bak \\10.2.66.30\g$\ynot_backup.A few points of interest:

• This command uses a UNC path (a path starting with two backslashes) to access the web server across the LAN. Specifically, \\10.2.66.30\g$ refers to the default share of the G: drive on the web server, and I've configured the permissions, both in the share and in the file system -- to give write access to authenticated users. (This is safe, because the share is accessible only to authenticated users using a non-routable private IP address on a local area network.)
• The /Y flag tells xcopy to overwrite any existing files without prompting the user for confirmation.

The above xcopy command works fine when executed in a DOS window on the database server. But to be able to schedule it, two changes are needed.

• First, we need to give the full path to xcopy.
• Second, we need to execute the command shell, cmd.exe, passing it the /c flag and the command to execute.

It ends up looking like this: C:\WINDOWS\system32\cmd.exe /c "xcopy /Y g:\SQLBackup\ynot_backup_*.bak \\10.2.66.30\g$\ynot_backup".

The final step is to go to Control Panel | Scheduled Tasks and create a new scheduled task to execute the above command at 7:30 AM each day. The only trick here is choosing an appropriate account under which to run the task. I chose an administrator account that has sufficient permissions and whose password doesn't change too frequently -- because each time the password changes, we must inform the scheduled task of the new password.

Now all I need to do is keep an eye on the web server and make sure the whole G: drive doesn't fill up with old database backups!