Generarea de SSH chei

Generam cheia publica pe masina de pe care vrem sa avem access

[root@xt-ipxqa3 .ssh]# ssh-keygen -t dsa
Generating public/private dsa key pair.
Enter file in which to save the key (/root/.ssh/id_dsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
3d:b3:a5:1a:15:2c:1c:ba:b7:b7:75:88:08:33:a5:54 root@xt-ipxqa3.cd
[root@xt-ipxqa3 .ssh]#

Continutul fisierului id_dsa.pub (/root/.ssh/id_dsa.pub, adica cheia publica) vezi mai jos i-l copiem in fisierul /root/.ssh/authorized_keys pe masina la care dorim sa avem acces fara a introduce parola.

[root@xt-ipxqa3 .ssh]# cat id_dsa.pub
ssh-dss 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 root@xt-ipxqa3.cd
[root@xt-ipxqa3 .ssh]#

In rezultat pe masina care dorim sa avem acces fisierul /root/.ssh/authorized_keys va arata in felul urmator:

[root@xt-ipxdev .ssh]# cat authorized_keys
ssh-dss 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 root@xt-ipxdev.cd
[root@xt-ipxdev .ssh]#


Dupa acest schimb de chei accesul de pe masina xt-ipxqa3 pe masina xt-ipxdev nu va fi authentificat prin parola, ex:

[root@xt-ipxqa3 .ssh]# ssh xt-ipxdev
Last login: Mon May 25 19:00:47 2009 from 172.16.34.239
[root@xt-ipxdev root]#

How to change ROOT password when it is lost on Red Hat

1. Reboot your system
2. When GRUB bootloader appear select "e" to edit boot options
3. Select to boot with following options: kernel /vmlinuz-2.4.21-20.EL ro root=LABEL=/ single , the word single need to be added at the end so you will boot in singlemode
4. When command shell appears go to: cd /etc
5. Using vi or other editors avilable select to edit passwd file, vi passwd
6. Look in the file for the line root:x:0:0:root:/root:/bin/bash and replace it with root::0:0:root:/root:/bin/bash, replace "x" with empty
7. Reboot in normal mode
8. When asking to enter the username, enter root username it will login without password, now useing command passwd enter the new password
9.