107

Is it possible to alias a hostname in Linux?

It has been asked by jmillikin at various Ubuntu forums as follows:

Is it possible to create a hostname alias? Sort of like /etc/hosts, but with other hostnames rather than IP addresses. So that with some file like this, you could ping "fakehost1", and it would be re-mapped to "realhost", and then "realhost" would be resolved to an IP address.

# Real host        # Aliases
realhost           fakehost1 fakehost2 fakehost3

Somebody has answered about ssh, but not about ping, etc. My main purpose is to use it as an alias for a Subversion server. In my case, realhost is under a dynamic IP address. So, the "/etc/hosts" alias doesn't work. I want to access my Subversion server as svn://my_svnserver/my_repos instead of svn://realhost/my_repos.

Peter Mortensen
  • 2,319
  • 5
  • 23
  • 24
  • I guess I may be missing something. Are you saying you couldn't have /etc/hosts look like 10.0.3.4 some.host.org another.domain.com You have to use a reference for some programmatic reason? – jim_m_somewhere Nov 16 '12 at 23:23

7 Answers7

75

For those who don't have an account on the forums (or don't wish to login):

if your main issue is not to ping but to ssh, you can create/edit your ~/.ssh/config adding lines like these:

Host fakehost1
  Hostname real-hostname

Host fakehost2
  Hostname real-hostname2

Host fakehost3
  Hostname real-hostname3
Te Ri
  • 109
  • 6
Xiong Chiamiov
  • 2,874
  • 2
  • 26
  • 30
  • 1
    The Hostname part needs to be on a new line. Here is a good tutorial on how to make a config file like this: http://mattryall.net/blog/2008/06/ssh-favourite-hosts – Code Commander Aug 06 '12 at 18:41
  • 1
    good workaround, thanks. But of course, better solution would be to use cnames on dns – Yuriy Vasylenko Jan 19 '16 at 22:54
40

Linux supports aliasing by setting the HOSTALIASES env variable.

echo "fakehost realhost" > /etc/host.aliases
echo "export HOSTALIASES=/etc/host.aliases" >> /etc/profile
. /etc/profile

then you can 

ping fakehost

N.B. ping requires you to set this up as root, but you can do it as any user for any application that runs as that user. ping suids to root.

teknopaul
  • 594
  • 4
  • 4
  • 4
    didn't work for me on Ubuntu 12.04 :( – Dimitry K Nov 17 '14 at 17:36
  • 3
    The HOSTALIASES only work for executables that are don't have the setuid flag set. So it won't work for ping (unless you're already root when executing ping). I guess this is done to avoid tricking setuid-executables into connecting to a different host than it intented. – Boris Jun 04 '15 at 14:13
  • 2
    Also does not work for curl – Benubird Jun 17 '15 at 09:55
  • Works great for maven with poms from Windows users :-) – selalerer Jul 19 '15 at 10:51
  • does not work on centos 6.4 either. – minghua Jun 09 '16 at 23:45
  • 7
    it will rarely end up in the expected result. **HOSTALIASES only works for applications using getaddrinfo(3) or gethostbyname(3)** - This mean that it will work for applications trying to explictly resolve the hostname by a specific system call: It is never the case. see http://unix.stackexchange.com/questions/10438/can-i-create-a-user-specific-hosts-file-to-complement-etc-hosts so the only solution is local dns (dnsmasq) – Nadir Sep 17 '16 at 09:19
  • 1
    Seems this is trick is deprecated. The gethostbyname*(), gethostbyaddr*(), herror(), and hstrerror() functions are obsolete. If your system runs DNSMasq locally you can alias in that for any resolution that uses DNS. – teknopaul Mar 16 '17 at 15:44
  • Does not work. When pinging, got the following: `ping: fakehost: No address associated with hostname` – Ashark Apr 02 '19 at 10:54
  • Ashark, try ping as root (with the env var), or try anything that does not use setuid to see if this works for your desired application. – teknopaul Apr 05 '19 at 15:05
  • teknopaul, yes pinging from root user works. – Ashark Apr 12 '19 at 05:12
  • Works for me on CentOS 8... – einpoklum Dec 03 '19 at 14:18
  • does not work on my debian 11.3 – Setop Jun 03 '22 at 08:57
26

You can setup this on your DNS server, CNAME records allow a machine to be known by more than one hostname. So add CNAME records to your DNS server like that : 


fakehost1 IN CNAME realhost 
fakehost2 IN CNAME realhost 
fakehost3 IN CNAME realhost
Ali Mezgani
  • 3,810
  • 2
  • 23
  • 36
21

I often do this with environment variables. I know this only works for the command line, but it is where I am most often craving hostname aliases (I worked with several supercomputer accounts, all with long URLs). Here's an example, if you're using BASH. In ~/.bashrc:

export fakehost="long.ass.annoying.url.org"

then, in a fresh shell:

ssh christopher@$fakehost

11

The only way this can be done is if you have your own local dns server.

theotherreceive
  • 8,235
  • 1
  • 30
  • 44
  • 1
    Yeah, now it seems the only solution. Thanks. Cannot upvote since I don't have enough reputation. –  Sep 14 '09 at 16:11
  • If the ever-changing IP address of a DSL or dialup connection is the issue, dyndns is a better solution, IMHO. – Sven Sep 14 '09 at 16:16
  • 1
    No, it's not a better solution. Once the server has a hostname that is handled by something else then all the OP needs is a CNAME for the first hostname. DYNDNS and similar rely on the host informing the dns server that it's ip has changed. – theotherreceive Sep 14 '09 at 16:37
6

You'll need an dyndns server that will map your current IP address to a hostname. You'll tell this server about your current IP address whenever you login, and it will update your hostname record.

Sven
  • 97,248
  • 13
  • 177
  • 225
5

The use of /etc/hosts.aliases is a standard feature of the bind resolver libraries. It's more robust than adding entries to /etc/hosts and can be used if you can not add CNAMES to your DNS (don't have access to it).

In general the best practice is to use CNAMES in the DNS with appropriate SEARCH defined in /etc/resolv.conf.

Updating /etc/hosts is not very robust as entries have to be kept in sync with IP changes. This only really works on a small scale or when you are using a name service to distribute the hosts map (eg via ldap).

Another solution may be DNSMasq http://en.wikipedia.org/wiki/Dnsmasq

Tom Hallam
  • 385
  • 3
  • 6
  • I tried using /etc/hosts.aliases in CENTOS 6 but this feature does not seem to work. Nor can I find any documentation on its use or existance. Where should I be looking? – mdpc Jun 15 '17 at 19:43