SQL Server service fails to start

SYMPTOMS

SQL server service fails to start in GINESYS POS application server. 
A error log, can be found in Windows Event viewer under 'Application' section for every service start-up failure. For example:

Event Source: Service Control Manager
Event ID: 9003

Description:

The log scan number (xxxxx) passed to log scan in database 'master' is not valid. This error may indicate data corruption or that the log file (.ldf) does not match the data file (.mdf). If this error occurred during replication, re-create the publication. Otherwise, restore from backup if the problem results in a failure during startup.

CAUSE

One of the system databases of SQL Server, the Master, got marked as invalid as there is a probable data corruption in the SQL Server database. There could be multiple reasons for that. The most common reason being one or several occasions of abnormal shutdown of that system where this Database service is installed.

RESOLUTION

Using Master Db Tool (MasterDBTools.exe), one can try to repair the Master database. 

Following article will guide further to use this tool:

How To: Use the Master DB Tool