How to get the previous hostname of my linux system? [closed]

Question

I have accidentally changed my system to host name. Now i want to change it to my previous host name. But i don't know the previous host name.

Answer 1

Have a look at these files:

/etc/hostname
/etc/hosts
/etc/ssh/ssh_host_*_key.pub
$HOME/.ssh/id_*.pub

In these typically the host name appears and it might be still unchanged by your renaming action (however you did that).

Also these might contain the old name:

/var/log/Xorg.failsafe.log
/var/log/auth.log.1
/var/log/pm-suspend.log.1
/var/log/Xorg.1.log.old
/var/log/lightdm/x-0.log
/var/log/lightdm/x-1.log
/var/log/lightdm/x-2.log
/var/log/pm-suspend.log
/var/log/Xorg.0.log.old
/var/log/Xorg.1.log
/var/log/syslog
/var/log/Xorg.2.log
/var/log/auth.log
/var/log/kern.log.1
/var/log/kern.log
/var/log/Xorg.failsafe.log.old
/var/log/syslog.1
/var/log/Xorg.0.log

Answer 2

In most cases HOSTNAME is defined in /etc/sysconfig/network file, to be set when boot. In some cases you can find it in /etc/hostname