What is the command to truncate a SQL Server log file?

In management studio:

• Don’t do this on a live environment, but to ensure you shrink your dev db as much as you can:
  • Right-click the database, choose Properties, then Options.
  • Make sure “Recovery model” is set to “Simple”, not “Full”
  • Click OK
• Right-click the database again, choose Tasks -> Shrink -> Files
• Change file type to “Log”
• Click OK.

Alternatively, the SQL to do it:

 ALTER DATABASE mydatabase SET RECOVERY SIMPLE
 DBCC SHRINKFILE (mydatabase_Log, 1)

Ref: http://msdn.microsoft.com/en-us/library/ms189493.aspx