Quick Assorted

Sep 13, 2015

Alter Tablespace with new data file

    ALTER TABLESPACE DEV_MDS
    ADD DATAFILE '/home/oracle/db11203/oradata/orcl/DEV_MDS3.dbf'
    SIZE 200M
    AUTOEXTEND ON
    NEXT 200M
    MAXSIZE UNLIMITED;

select a.tablespace_name,
round(a.bytes_alloc / 1024 / 1024) megs_alloc,
round(nvl(b.bytes_free, 0) / 1024 / 1024) megs_free,
       round((a.bytes_alloc - nvl(b.bytes_free, 0)) / 1024 / 1024) megs_used,
      round((nvl(b.bytes_free, 0) / a.bytes_alloc) * 100) Pct_Free,
       100 - round((nvl(b.bytes_free, 0) / a.bytes_alloc) * 100) Pct_used,
       round(maxbytes/1048576) Max,
      c.status, c.contents
from ( select f.tablespace_name,
               sum(f.bytes) bytes_alloc,
               sum(decode(f.autoextensible, 'YES',f.maxbytes,'NO', f.bytes)) maxbytes
        from dba_data_files f
        group by tablespace_name) a,
      ( select f.tablespace_name,
               sum(f.bytes) bytes_free
        from dba_free_space f
        group by tablespace_name) b,
      dba_tablespaces c
where a.tablespace_name = b.tablespace_name(+)
and a.tablespace_name = c.tablespace_name
union all
select h.tablespace_name,
       round(sum(h.bytes_free + h.bytes_used) / 1048576) megs_alloc,
       round(sum((h.bytes_free + h.bytes_used) - nvl(p.bytes_used, 0)) / 1048576) megs_free,
       round(sum(nvl(p.bytes_used, 0))/ 1048576) megs_used,
       round((sum((h.bytes_free + h.bytes_used) - nvl(p.bytes_used, 0)) / sum(h.bytes_used + h.bytes_free)) * 100) Pct_Free,
       100 - round((sum((h.bytes_free + h.bytes_used) - nvl(p.bytes_used, 0)) / sum(h.bytes_used + h.bytes_free)) * 100) pct_used,
       round(sum(decode(f.autoextensible, 'YES', f.maxbytes, 'NO', f.bytes) / 1048576)) max,
      c.status, c.contents
from   sys.v_$TEMP_SPACE_HEADER h,
       sys.v_$Temp_extent_pool p,
       dba_temp_files f,
     dba_tablespaces c
where p.file_id(+) = h.file_id
and    p.tablespace_name(+) = h.tablespace_name
and    f.file_id = h.file_id
and    f.tablespace_name = h.tablespace_name
and f.tablespace_name = c.tablespace_name
group by h.tablespace_name, c.status, c.contents
ORDER BY 1

Jul 8, 2015

How to Configure Proxy Settings in Linux

Redhat/Fedora – Yum Package Manager

yum proxy settings can be found in the file system at
/etc/yum.conf

Add a line to the file with the following information:
proxy=http://proxy-server:port

The next time you run yum, it will pick up that proxy.

Jun 16, 2015

Error Message: "The local device name is already in use"

Use command "net use W: /delete" to remove the mapped drive

Jan 30, 2015

[HTTP:101216]Servlet: "" failed to preload on startup in Web application: "". java.lang.NullPointerException

Exception while deploying the WebService application having ports defined for http & jms.

#### <[ACTIVE] ExecuteThread: '1' for queue: 'weblogic.kernel.Default (self-tuning)'> <> <1422607756443> java.lang.NullPointerException
    at weblogic.wsee.wsdl.soap11.SoapBindingOperation.narrow(SoapBindingOperation.java:82)
    at weblogic.wsee.ws.WSBuilderHelper.populateParts(WSBuilderHelper.java:1206)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperation(WSBuilderHelper.java:370)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperations(WSBuilderHelper.java:345)
    at weblogic.wsee.ws.WSBuilderHelper.populatePort(WSBuilderHelper.java:244)
    at weblogic.wsee.ws.WSBuilderHelper.buildWsPort(WSBuilderHelper.java:195)
    at weblogic.wsee.ws.WSBuilderHelper.buildService(WSBuilderHelper.java:88)
    at weblogic.wsee.ws.WsBuilder.buildService(WsBuilder.java:197)
    at weblogic.wsee.ws.WsFactory.createServerService(WsFactory.java:54)
    at weblogic.wsee.deploy.ServletDeployInfo.createWsService(ServletDeployInfo.java:91)
    at weblogic.wsee.deploy.DeployInfo.createWsPort(DeployInfo.java:381)
    at weblogic.wsee.server.servlet.BaseWSServlet.init(BaseWSServlet.java:83)
    at javax.servlet.GenericServlet.init(GenericServlet.java:241)
    at weblogic.servlet.internal.StubSecurityHelper$ServletInitAction.run(StubSecurityHelper.java:283)
    at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
    at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
    at weblogic.servlet.internal.StubSecurityHelper.createServlet(StubSecurityHelper.java:64)
    at weblogic.servlet.internal.StubLifecycleHelper.createOneInstance(StubLifecycleHelper.java:58)
    at weblogic.servlet.internal.StubLifecycleHelper.(StubLifecycleHelper.java:48)
    at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:539)
    at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1984)
    at weblogic.servlet.internal.WebAppServletContext.loadServletsOnStartup(WebAppServletContext.java:1958)
    at weblogic.servlet.internal.WebAppServletContext.preloadResources(WebAppServletContext.java:1877)
    at weblogic.servlet.internal.WebAppServletContext.start(WebAppServletContext.java:3173)
    at weblogic.servlet.internal.WebAppModule.startContexts(WebAppModule.java:1527)
    at weblogic.servlet.internal.WebAppModule.start(WebAppModule.java:486)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.ScopedModuleDriver.start(ScopedModuleDriver.java:200)
    at weblogic.application.internal.flow.ModuleListenerInvoker.start(ModuleListenerInvoker.java:247)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.StartModulesFlow.activate(StartModulesFlow.java:27)
    at weblogic.application.internal.BaseDeployment$2.next(BaseDeployment.java:671)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.BaseDeployment.activate(BaseDeployment.java:212)
    at weblogic.application.internal.EarDeployment.activate(EarDeployment.java:59)
    at weblogic.application.internal.DeploymentStateChecker.activate(DeploymentStateChecker.java:161)
    at weblogic.deploy.internal.targetserver.AppContainerInvoker.activate(AppContainerInvoker.java:80)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.activate(AbstractOperation.java:573)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.activateDeployment(ActivateOperation.java:150)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.doCommit(ActivateOperation.java:116)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.commit(AbstractOperation.java:327)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleDeploymentCommit(DeploymentManager.java:844)
    at weblogic.deploy.internal.targetserver.DeploymentManager.activateDeploymentList(DeploymentManager.java:1253)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleCommit(DeploymentManager.java:440)
    at weblogic.deploy.internal.targetserver.DeploymentServiceDispatcher.commit(DeploymentServiceDispatcher.java:163)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.doCommitCallback(DeploymentReceiverCallbackDeliverer.java:195)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.access$100(DeploymentReceiverCallbackDeliverer.java:13)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer$2.run(DeploymentReceiverCallbackDeliverer.java:68)
    at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:545)
    at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
    at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)

    at weblogic.wsee.wsdl.soap11.SoapBindingOperation.narrow(SoapBindingOperation.java:82)
    at weblogic.wsee.ws.WSBuilderHelper.populateParts(WSBuilderHelper.java:1206)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperation(WSBuilderHelper.java:370)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperations(WSBuilderHelper.java:345)
    at weblogic.wsee.ws.WSBuilderHelper.populatePort(WSBuilderHelper.java:244)
    at weblogic.wsee.ws.WSBuilderHelper.buildWsPort(WSBuilderHelper.java:195)
    at weblogic.wsee.ws.WSBuilderHelper.buildService(WSBuilderHelper.java:88)
    at weblogic.wsee.ws.WsBuilder.buildService(WsBuilder.java:197)
    at weblogic.wsee.ws.WsFactory.createServerService(WsFactory.java:54)
    at weblogic.wsee.deploy.ServletDeployInfo.createWsService(ServletDeployInfo.java:91)
    at weblogic.wsee.deploy.DeployInfo.createWsPort(DeployInfo.java:381)
    at weblogic.wsee.server.servlet.BaseWSServlet.init(BaseWSServlet.java:83)
    at javax.servlet.GenericServlet.init(GenericServlet.java:241)
    at weblogic.servlet.internal.StubSecurityHelper$ServletInitAction.run(StubSecurityHelper.java:283)
    at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
    at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
    at weblogic.servlet.internal.StubSecurityHelper.createServlet(StubSecurityHelper.java:64)
    at weblogic.servlet.internal.StubLifecycleHelper.createOneInstance(StubLifecycleHelper.java:58)
    at weblogic.servlet.internal.StubLifecycleHelper.(StubLifecycleHelper.java:48)
    at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:539)
    at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1984)
    at weblogic.servlet.internal.WebAppServletContext.loadServletsOnStartup(WebAppServletContext.java:1958)
    at weblogic.servlet.internal.WebAppServletContext.preloadResources(WebAppServletContext.java:1877)
    at weblogic.servlet.internal.WebAppServletContext.start(WebAppServletContext.java:3173)
    at weblogic.servlet.internal.WebAppModule.startContexts(WebAppModule.java:1527)
    at weblogic.servlet.internal.WebAppModule.start(WebAppModule.java:486)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.ScopedModuleDriver.start(ScopedModuleDriver.java:200)
    at weblogic.application.internal.flow.ModuleListenerInvoker.start(ModuleListenerInvoker.java:247)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.StartModulesFlow.activate(StartModulesFlow.java:27)
    at weblogic.application.internal.BaseDeployment$2.next(BaseDeployment.java:671)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.BaseDeployment.activate(BaseDeployment.java:212)
    at weblogic.application.internal.EarDeployment.activate(EarDeployment.java:59)
    at weblogic.application.internal.DeploymentStateChecker.activate(DeploymentStateChecker.java:161)
    at weblogic.deploy.internal.targetserver.AppContainerInvoker.activate(AppContainerInvoker.java:80)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.activate(AbstractOperation.java:573)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.activateDeployment(ActivateOperation.java:150)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.doCommit(ActivateOperation.java:116)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.commit(AbstractOperation.java:327)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleDeploymentCommit(DeploymentManager.java:844)
    at weblogic.deploy.internal.targetserver.DeploymentManager.activateDeploymentList(DeploymentManager.java:1253)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleCommit(DeploymentManager.java:440)
    at weblogic.deploy.internal.targetserver.DeploymentServiceDispatcher.commit(DeploymentServiceDispatcher.java:163)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.doCommitCallback(DeploymentReceiverCallbackDeliverer.java:195)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.access$100(DeploymentReceiverCallbackDeliverer.java:13)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer$2.run(DeploymentReceiverCallbackDeliverer.java:68)
    at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:545)
    at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
    at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)
    at weblogic.servlet.internal.WebAppModule.startContexts(WebAppModule.java:1529)
    at weblogic.servlet.internal.WebAppModule.start(WebAppModule.java:486)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.ScopedModuleDriver.start(ScopedModuleDriver.java:200)
    at weblogic.application.internal.flow.ModuleListenerInvoker.start(ModuleListenerInvoker.java:247)
    at weblogic.application.internal.flow.ModuleStateDriver$3.next(ModuleStateDriver.java:425)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.flow.ModuleStateDriver.start(ModuleStateDriver.java:119)
    at weblogic.application.internal.flow.StartModulesFlow.activate(StartModulesFlow.java:27)
    at weblogic.application.internal.BaseDeployment$2.next(BaseDeployment.java:671)
    at weblogic.application.utils.StateMachineDriver.nextState(StateMachineDriver.java:52)
    at weblogic.application.internal.BaseDeployment.activate(BaseDeployment.java:212)
    at weblogic.application.internal.EarDeployment.activate(EarDeployment.java:59)
    at weblogic.application.internal.DeploymentStateChecker.activate(DeploymentStateChecker.java:161)
    at weblogic.deploy.internal.targetserver.AppContainerInvoker.activate(AppContainerInvoker.java:80)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.activate(AbstractOperation.java:573)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.activateDeployment(ActivateOperation.java:150)
    at weblogic.deploy.internal.targetserver.operations.ActivateOperation.doCommit(ActivateOperation.java:116)
    at weblogic.deploy.internal.targetserver.operations.AbstractOperation.commit(AbstractOperation.java:327)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleDeploymentCommit(DeploymentManager.java:844)
    at weblogic.deploy.internal.targetserver.DeploymentManager.activateDeploymentList(DeploymentManager.java:1253)
    at weblogic.deploy.internal.targetserver.DeploymentManager.handleCommit(DeploymentManager.java:440)
    at weblogic.deploy.internal.targetserver.DeploymentServiceDispatcher.commit(DeploymentServiceDispatcher.java:163)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.doCommitCallback(DeploymentReceiverCallbackDeliverer.java:195)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer.access$100(DeploymentReceiverCallbackDeliverer.java:13)
    at weblogic.deploy.service.internal.targetserver.DeploymentReceiverCallbackDeliverer$2.run(DeploymentReceiverCallbackDeliverer.java:68)
    at weblogic.work.SelfTuningWorkManagerImpl$WorkAdapterImpl.run(SelfTuningWorkManagerImpl.java:545)
    at weblogic.work.ExecuteThread.execute(ExecuteThread.java:256)
    at weblogic.work.ExecuteThread.run(ExecuteThread.java:221)
Caused by: java.lang.NullPointerException:
    at weblogic.wsee.wsdl.soap11.SoapBindingOperation.narrow(SoapBindingOperation.java:82)
    at weblogic.wsee.ws.WSBuilderHelper.populateParts(WSBuilderHelper.java:1206)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperation(WSBuilderHelper.java:370)
    at weblogic.wsee.ws.WSBuilderHelper.populateOperations(WSBuilderHelper.java:345)
    at weblogic.wsee.ws.WSBuilderHelper.populatePort(WSBuilderHelper.java:244)
    at weblogic.wsee.ws.WSBuilderHelper.buildWsPort(WSBuilderHelper.java:195)
    at weblogic.wsee.ws.WSBuilderHelper.buildService(WSBuilderHelper.java:88)
    at weblogic.wsee.ws.WsBuilder.buildService(WsBuilder.java:197)
    at weblogic.wsee.ws.WsFactory.createServerService(WsFactory.java:54)
    at weblogic.wsee.deploy.ServletDeployInfo.createWsService(ServletDeployInfo.java:91)
    at weblogic.wsee.deploy.DeployInfo.createWsPort(DeployInfo.java:381)
    at weblogic.wsee.server.servlet.BaseWSServlet.init(BaseWSServlet.java:83)
    at javax.servlet.GenericServlet.init(GenericServlet.java:241)
    at weblogic.servlet.internal.StubSecurityHelper$ServletInitAction.run(StubSecurityHelper.java:283)
    at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
    at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:120)
    at weblogic.servlet.internal.StubSecurityHelper.createServlet(StubSecurityHelper.java:64)
    at weblogic.servlet.internal.StubLifecycleHelper.createOneInstance(StubLifecycleHelper.java:58)
    at weblogic.servlet.internal.StubLifecycleHelper.(StubLifecycleHelper.java:48)
    at weblogic.servlet.internal.ServletStubImpl.prepareServlet(ServletStubImpl.java:539)
    at weblogic.servlet.internal.WebAppServletContext.preloadServlet(WebAppServletContext.java:1984)
    at weblogic.servlet.internal.WebAppServletContext.loadServletsOnStartup(WebAppServletContext.java:1958)
    at weblogic.servlet.internal.WebAppServletContext.preloadResources(WebAppServletContext.java:1877)
    at weblogic.servlet.internal.WebAppServletContext.start(WebAppServletContext.java:3173)
    at weblogic.servlet.internal.WebAppModule.startContexts(WebAppModule.java:1527)
>

Solution: This kind of issues were occur when the operation(s) is/are defined either one of the bindings (http or jms). Please check the for all operation defined for http and jms ports

Jan 28, 2015

Weblogic command-line deployment

Weblogic command-line deployment in Linux with Java

1. Set java to PATH
2. Go to $WLS_HOME/server/bin
3. perform ". setWLSEnv.sh" - to set weblogic jars to classpath.
4. perform "echo $CLASSPATH" to check whether jars are properly set to classpath.
5. java weblogic.Deployer -adminurl http://: -username -password -deploy -name -source -targets -securityModel -plan

eg: java weblogic.Deployer -adminurl http://192.168.0.2:7001 -username weblogic -password weblogic1 -deploy -name HelloWorld -source /opt/sureshba/HelloWorld.ear -targets AdminServer -securityModel CustomRoles -plan /opt/sureshba/plan/HelloWorld.xml

For more info: http://docs.oracle.com/cd/E13222_01/wls/docs90/deployment/wldeployer.html

Nov 12, 2014

Router vs Switch

	Router	Switch
Layer	Network Layer (Layer 3 devices)	Data Link Layer. Network switches operate at Layer 2 of the OSI model.
Ports	2/4/8	Switch is multi port Bridge. 24/48 ports
Device Type	Networking device	Active Device (With Software) & Networking device
Data Transmission form	Packet	Frame (L2 Switch) Frame & Packet (L3 switch)
Transmission Type	At Initial Level Broadcast then Uni-cast & Multicast	First broadcast; then unicast & multicast as needed.
Function	Directs data in a network. Passes data between home computers, and between computers and the modem.	Allow to connect multiple device and port can be manage, Vlan can create security also can apply
Table	Store IP address in Routing table and maintain address at its own.	A network switch stores MAC addresses in a lookup table.
Transmission Mode	Full duplex	Full duplex
Used in (LAN, MAN, WAN)	LAN, WAN	LAN
Broadcast Domain	In Router, every port has its own Broadcast domain.	Switch has one broadcast domain [unless VLAN implemented]
Definition	A router is a networking device that connects a local network to other local networks. At the Distribution Layer of the network, routers direct traffic and perform other functions critical to efficient network operation.	A network switch is a computer networking device that is used to connect many devices together on a computer network. A switch is considered more advanced than a hub because a switch will on send msg to device that needs or request it
Device Category	Intelligent Device	Intelligent Device
Bandwidth sharing	Bandwidth sharing is Dynamic (Enables either static or dynamic bandwidth sharing for modular cable interfaces. The default percent-value is 0. The percent-value range is 1-96.)	There no sharing port can be 10, 100, 1000 and 10000 Mbps individual
Speed	1-10 Mbps(Wireless) 100 Mbps (Wired)	10/100Mbps, 1Gbps
Routing Decision	Take faster Routing Decision	Take more time for complicated routing Decision
NAT (Network Address Translation)	Can Perform NAT	Switches can Not perform NAT
Faster	In a different network environment (MAN/ WAN) Router is faster than L3 Switch.	In a LAN environment L3 switch is faster than Router (built in switchning hardware)
Features	Firewall VPN Dynamic hadling of Bandwidth	Priority rt range On/Off setting of port VLAN Port mirroring
Latest Models	Linksys WRT54GL Juniper MX & EX series Cisco 3900,2900,1900	Alcatel's OmniSwitch 9000; Cisco Catalyst switch 4500 and 6500(10 Gbps),
Used for	Connecting two or more networks	Connecting two or more nodes in the same network or different network
Address used for data tramsmission	Uses IP address	Uses MAC address

Source: http://www.diffen.com/difference/Router_vs_Switch

Oct 28, 2014

Reset forgotten/lost main user password in Linux

You can reset your password following the next steps:

Reboot your computer / Turn your computer on.
Hold down the Shift key at the start of the boot process to enable the GNU GRUB boot menu (if it does not show)
Press ESC at the GNU GRUB prompt.
Press e for edit.
Use the Arrow keys to highlight the line that begins with kernel and press the e key.
Go to the very end of the line and add rw init=/bin/bash
Press Enter and then press b to boot your system.
Your system will boot up to a passwordless root shell.
Type in passwd yourusername
Set your new password.
Restart your system.

Note:- Above steps only work with Linux installed with 'grub'

Source:http://community.linuxmint.com/tutorial/view/339