How do you backup a database within SQL Server 2005 from the command line?
Solution 1:
OSQL -E -Q "BACKUP DATABASE database_name TO DISK = 'path and filename'"
As in:
OSQL -E -Q "BACKUP DATABASE master TO DISK = 'C:\master.bak'"
Be sure you're running that as a user who has rights to backup that database (or, alternatively, use the "-U" and "-P" arguments to supply a username/password on the command line... not a good idea, thought.)
Solution 2:
Actually better here is to use SQLCMD instead of OSQL. OSQL is considered deprecated as of SQL Server 2005, though it's still around in SQL Server 2008.