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Overview of Unix
Activity Guide11
[Edition 1]
[Last Update 130815]
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Administering Remote System in Linux
- 1. If there is any issue at setup or connection contact support@k21technologies.com Overview of Unix Activity Guide11 [Edition 1] [Last Update 130815] For any issues/help contact : support@k21technologies.com
- 2. If there is any issue at setup or connection contact support@k21technologies.com Administering Remote System There are couple of waysthat youcan access a shell(commandline) remotelyonmostLINUX/UNIX systems.One of the olderwaysisto use the telnetprogram, whichis available onmostnetworkcapable operatingsystems.Accessingashell accountthroughthe telnetmethodthoughposesadangerinthat everythingthatyousendorreceive overthattelnetsessionisvisibleinplaintexton yourlocal network, and the local networkof the machine youare connectingto.Soanyone whocan "sniff"the connection inbetweencansee yourusername,password,email thatyouread,andcommandthat yourun. For these reasonsyouneedamore sophisticated programthantelnettoconnecttoa remote host. SSH, whichisan acronymfor secure shell,wasdesignedandcreatedtoprovide the bestsecuritywhen accessinganothercomputerremotely,Notonlydoesitencryptthe session,italsoprovidesbetter authenticationfacilities. SSH configurationfile is /etc/ssh/sshd_config SSH daemonor service is sshd Accessingthe remote machine using ssh Syntax: ssh<ip address/ host name ofremote machine> Note:hostname canonlybe usedwhenthe hostname issavedin/etc/hostsfile or,if DNSisconfigured The firsttime aroundit will askyouif you wishtoadd the remote hostto a listof known_hosts,go aheadand say yes Enter the passwordof the remote systemcorrectly,onnce loggedincheckhostname andipaddressto confirmlogin.
- 3. If there is any issue at setup or connection contact support@k21technologies.com To leave the session,justtype exitorlogoutcommandandyouwill be back to your ownmachine throughwhichyouare loggedin PasswordlessloginusingSSHKeys As a systemadmin,one personwillbe assignedtomanage manysystems,forexampleone person hasto manage more than10 systemsat a time.Inthissituationadminhas to transfer some filesfromone systemtoanother9 systemsorvice versa,foreveryloginonremote system it will promptforpassword.Evenfortransferringfilesforeverytransferwe needtoenterthe password. Above situationwill be be veryannoying forsystemadmintotype passwordforeverystep. therefore SSHprovidesabestwayto escape passwordpromptingeverynow andthen. By generatingSSHkeys,apublickeyandaprivate key,anadmincancopy the publickeyinto othersystemanddone,itwill workas authorizedaccessfromthe admin'ssystem.Now wheneverwe are loggingfromadmin'ssystemtoothersysteminwhichwe have storedthe publickeyof admin'ssystem,itwill notpromptusfor passwordandwe can loginto that system as many time as we want withoutbeingpromptforthe password. SSH keysare an implementationof public-keycryptography.Theysolvethe problemof brute- force passwordattacks bymakingthemcomputationallyimpractical.
- 4. If there is any issue at setup or connection contact support@k21technologies.com PublickeycryptographyusesaPUBLIC KEY to encrypt data and a PRIVATEKEY to decryptit. It will promptabove tomentionthe file where thesekeysshouldbe stored,tokeepitsdefaultdirectory justpress "Enter". The defaultlocationwill be /root/.ssh/directory Nowit will askforpassphrase, whichwillbe usedinsteadof password.The passphrase will onlybe askedonce persession.Enteryourdesired passphrase twice asshownonnextpage,andpressenter Okaynow our keysare successfullygenerated,goto/root/.ssh/directoryandcheckfor the keys. The id_rsa isa private keyand id_rsa.pub isthe publickeywhichwill be usedlatertomake password lesslogin Copyingthe publickeyonclientsystem(some otherserver/node) to copy the server'spublickeyinthe clientsystem,the commandis
- 5. If there is any issue at setup or connection contact support@k21technologies.com #ssh-copy-id -i<publickeylocation><clientsIPaddress>(oruser@ clientIP) #ssh-copy-id -i/root/.ssh/id_rsa.pub 192.168.10.95 =============End of the Activity 11 Guide========