Linux – Changing hostname reboot reverts back to original

hostnamelinux

So, What I'm trying to do is simply change the hostname permanently. I can update the hostname but when a reboot is issued the original hostname is used!

I'm aware there is a file hostname located at: /etc/hostname. I update this file and issue a reboot, however the hostname is back to the previous setting!

What I've tried:

Updating /etc/hosts file newhostname
Updating hosts file – 127.0.0.1 newhostname
reboot

I've also tried with sudo user and root!

Why is this happening?!

Thanks for any advice or suggestions, I feel like I've tried every other solution with no avail.

EDIT:

I've just updated the /etc/hostname file on a VM running debian 7 locally and it works as expected. Why doesn't this work when connected to a remote server with SSH?

Best Answer

hostnamectl set-hostname servername.example.com

That's for RHEL 7 that is.

Related Solutions

In which file is hostname alias persistent, if not /etc/hosts

If you are on Fedora / RHEL / CentOS, the hostname is set by the rc.sysinit script after retrieving the desired value from the /etc/sysconfig/network file.

As to why it can only be changed once per boot - it can be changed anytime. You have to provide a new hostname to the hostname command to change it, just editing a file won't do so. Keep in mind though that if you change it this way, any programs that were running before you changed it may still have the old value cached.

Linux – Where does `hostname` store the hostname that I’ve set

Take a look at this related U&L Q&A titled: Where does uname get its information from?. Information such as the hostname persists within a data structure within the Linux kernel, while the system is running. During a system's boot this information can be reattained through a variety of mechanisms that is typically distro specific.

If you look at the man 2 uname man page there's a data structure mentioned there:

           struct utsname {
               char sysname[];    /* Operating system name (e.g., "Linux") */
               char nodename[];   /* Name within "some implementation-defined
                                     network" */
               char release[];    /* Operating system release (e.g., "2.6.28") */
               char version[];    /* Operating system version */
               char machine[];    /* Hardware identifier */
           #ifdef _GNU_SOURCE
               char domainname[]; /* NIS or YP domain name */
           #endif
           };

The 2nd element of that structure, nodename[] is one place where the hostname is stored within the Linux kernel.

/proc

If you take a look at /proc/sys/kernel/hostname, the hostname is exposed here as well. This is a virtual location, /proc, but it does give you an alternative method for accessing the hostname. The system's domainname is here too, /proc/sys/kernel/domainname.

NOTE: Of interest, these values are UTS namespace specific.

Example

$ sudo hostname
oldhost
$ sudo unshare --uts /bin/bash
$ sudo echo newhost > /proc/sys/kernel/hostname 
$ hostname
newhost
$ exit
$ hostname
oldhost

Manipulating the hostname

On system's with Systemd you can use the cli tool hostnamectl to get/set the hostname. This will change it permanently between reboots.

$ sudo hostnamectl set-hostname --static somehostname

You can also find out it's value through sysctl:

$ sudo sysctl -a | grep kernel.hostname
kernel.hostname = myhostname

For Fedora releases, this ask.fedoraproject.org Q&A covers the topic pretty thoroughly, titled: Correctly setting the hostname - Fedora 20 on Amazon EC2.