SSH login without password

SSHloginwithoutpassword

Youraim

YouwanttouseLinuxandOpenSSHtoautomizeyourtasks.ThereforeyouneedanautomaticloginfromhostA/useratoHostB/userb.Youdon'twanttoenteranypasswords,becauseyouwanttocallsshfromawithinashellscript.

Howtodoit

Step1:Generatepubkeyinsshserverwithoutpassword"ssh-keygen-trsa"

Step2:Copythepubkeytosshclientfile"~/.ssh/authorized_keys"

Step3:Accessthesshserverfromsshclientuse"sshusername@ip"

Step4:Checkthesshclientfile~/.ssh/known_hostsand~/.ssh/authorized_keyshasthematchedipaddress.

FirstloginonAasuseraandgenerateapairofauthenticationkeys.Donotenterapassphrase:

a@A:~> ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/a/.ssh/id_rsa): 
Created directory '/home/a/.ssh'.
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/a/.ssh/id_rsa.
Your public key has been saved in /home/a/.ssh/id_rsa.pub.
The key fingerprint is:
3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Nowusesshtocreateadirectory~/.sshasuserbonB.(Thedirectorymayalreadyexist,whichisfine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password:

Finallyappenda'snewpublickeytob@B:.ssh/authorized_keysandenterb'spasswordonelasttime:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password:

FromnowonyoucanlogintoBasbfromAasawithoutpassword:

a@A:~> ssh b@B hostname
B

Anotefromoneofourreaders:DependingonyourversionofSSHyoumightalsohavetodothefollowingchanges:

* Put the public key in .ssh/authorized_keys2
    * Change the permissions of .ssh to 700
    * Change the permissions of .ssh/authorized_keys2 to 640