SAP Basis Consultants manage lot of Operating system level commands, some major commands i listed here, 

Commands	Description
dpmon d	Dispatcher queue monitor
PS	Running work process
ps -eaf|grep dw	Process overview
ps -eaf|grep ora	Check oracle service is running
Ps –eaf | grep dw kill -9	Kill work process
msmon pf=profile path name=sid	Check the message server status
gwmon pf=profile path nr=num	Check the gateway status
Ps –eaf | grep lsnrctl	Listener status
Rslgview pf =-r –ft | pg	System logs
Disp + work –v	Check the version of r3 kernel
R3trans –d ,tnsping	Checking the connection with database
Df –k	File system monitor
saplicence  -get	Get hardware key
saplicense -install	Install SAP license
sappfpar all pf=profile path	Display all profile parameters
sappfpar check path=profile path	Checks the required space for memory
memlimits	Check the available space for heap memory and swap memory
telnet	Remote system login
telnet <ipaddress><dispatcherportnum>	Check the remote sap system is up and running
ftp	File transfer protocol
rcp	Remote copy of files
start/stop sap	Start / Stop Sap instance
ping	Check destination host reachable
niping	Check connection between server and a client by transferring packets
systeminfo	Check the configuration of system
Ps -aef	Processes status
lsps -a	Swap space
topas	Memory

hope it helps you...