Can I create override dns similar to writing in /etc/hosts without root access

Question

I want to set a dns record that my browser will use, but I don't have root access, so I can't modify /etc/hosts. I need to do this for testing vhosts with apache, whose dns hasn't yet been set up. I have access to firefox, and chrome, so if there's a plugin that could facilitate it; or other options are helpful.

update: the alternative to overriding the dns is probably modifying the HTTP headers, if the correct ones are sent to apache, the correct content should be returned.

The last line is unclear. Also, wouldn't this fit more in SF? — tshepang, Feb 04 '11 at 08:40
@tshepang ... no because I need to do this on a linux desktop? — xenoterracide, Feb 04 '11 at 10:03
Still not so clear. What does "or other options are helpful" mean exactly? Don't make me guess. — tshepang, Feb 04 '11 at 10:53
@tshepang I don't know what I'm looking for... if I knew why would I be asking? there might be options that I haven't considered. I feel like you're asking me to explain how apache virtual hosts, http, and dns work together. — xenoterracide, Feb 06 '11 at 05:20
I think you're looking for this: https://unix.stackexchange.com/a/104511/135943 — Wildcard, Jul 03 '17 at 21:42

score 75 · Accepted Answer · edited Jan 07 '16 at 08:37

75

I was looking for a way to run a program with modified DNS resolution for testing purposes. For me, the solution was using the HOSTALIASES environment variable:

$ echo "foo www.google.com" >> ~/.hosts
$ HOSTALIASES=~/.hosts wget foo

See hostname(7).

(Side note: In the example the HOSTALIASES environment variable only affects the wget process. Of course, you can export HOSTALIASES to have it take effect for all subprocesses of the current shell.)

edited Jan 07 '16 at 08:37

Community

1

answered Nov 21 '12 at 11:37

matlehmann

976

1

really this should be like +10k, unfortunately I can only give you +1 – xenoterracide Nov 21 '12 at 22:03
I agree! +10k!! – Anders Hansson Sep 21 '13 at 16:45
3

Thanks a lot! The example should prepend export in most cases: export HOSTALIASES=~/.hosts. – ezequiel-garzon Apr 26 '14 at 22:04
11

it seems only support hosts to hosts alias, not IP and hosts can not contain ".". – netawater Apr 16 '15 at 05:26
Is there the same solution for Windows? – Akceptor Jun 09 '17 at 07:39
For a one-time use, in some shells (e.g. zsh) the following one-liner works: HOSTALIASES==(printf 'foo www.google.com') wget foo – liori Aug 30 '17 at 18:03
One weak point, this doesn't work for setuid root programs, like ping and ssh – jmd Mar 24 '22 at 12:40

score 11 · Answer 2 · answered Feb 04 '11 at 14:14

11

You can write a wrapper around the libc function to resolve hostnames and look them up in a different file than /etc/hosts. Then run any application you'd like to use your hosts file with

LD_PRELOAD=wrapper.so firefox

answered Feb 04 '11 at 14:14

chris

1,142

5

Most usefully, make your wrapper redirect the opening of /etc/nsswitch.conf to ~/.nsswitch.conf, and make a ~/.nsswitch.conf that queries your DNS databases. – Gilles 'SO- stop being evil' Feb 04 '11 at 23:49

score 6 · Answer 3 · answered Feb 04 '11 at 14:30

I think the best way to do this would be to set up a SOCKS5 proxy and tell firefox to send the DNS requests over the SOCKS5 proxy (network.proxy.socks_remote_dns). You could set up a socks5 proxy with openssh fairly easily (the -D option) and have a remote host running with a custom /etc/hosts, or something like DNSMasq for more complex DNS settings. Effectively, though, this is pushing the configuration of the DNS settings to a system you can make system-wide changes to.

easier said than done, considering the great firewall that's been erected to block us from ssh-ing out... — xenoterracide, Feb 06 '11 at 05:21

score 5 · Answer 4 · edited Mar 20 '17 at 10:18

5

Check out following question at superuser:

https://superuser.com/questions/184643/override-dns-in-firefox

If the discussed options and the SO link are not viable solutions then check out:

https://superuser.com/questions/100239/hostname-override-in-firefox

Especially check out:

https://addons.mozilla.org/en-US/firefox/addon/redirector/

It sounds like this addon could help - but I depends on its actual implementation.

edited Mar 20 '17 at 10:18

Community

1

answered Feb 04 '11 at 08:41

maxschlepzig

57,532

unfortunately much like the op in that question none of these seem viable. – xenoterracide Feb 04 '11 at 10:28
@xenoterracide - I updated my answer - perhaps the redirector add-on is an option? – maxschlepzig Feb 04 '11 at 19:38
I don't think so from the way it's worded.. what I really need to do is modify the HTTP headers that are sent... as an alternative option to hacking around using hosts – xenoterracide Feb 06 '11 at 05:14
I poked around the SO solution (TamperData) but I didn't see how to modify the host in that. I wonder if the live http headers thing really does allow me to modify headers, it says it's a viewer. – xenoterracide Feb 06 '11 at 05:18
I think the Modify Headers extension listed down a bit in the SO one works... if you use Host hostname... in it... not yet tested... outside of breaking sites using it. – xenoterracide Feb 06 '11 at 05:32

score 2 · Answer 5 · answered Feb 06 '11 at 22:42

2

To test vhosts, you might set the Apache server as the proxy in Firefox. The name you entered will be forwarded to Apache. This will break browsing other sites so set the proxy back when you are done.

answered Feb 06 '11 at 22:42

BillThor

8,965

score 0 · Answer 6 · answered Feb 10 '21 at 18:26

overlayfs + chroot : )

problem: mount requires root access

#!/bin/sh
D=/tmp/my-overlay
mkdir -p $D/{upper,work,merged}
mount -t overlay overlay -o lowerdir=/,upperdir=$D/upper,workdir=$D/work $D/merged
echo '1.2.3.4 myhost' >>$D/merged/etc/hosts
chroot $D/merged wget http://myhost/

score 0 · Answer 7 · answered Aug 21 '22 at 03:27

It is possible to override dns resolution in google chrome in windows, mac and linux without root/admin access. All we need to do is to start google chrome process with a switch and supply the required DNS entries there.

https://devopslife.io/resolve-dns-locally-using-google-chrome/

score -1 · Answer 8 · answered May 17 '16 at 07:53

I needed something similar for ssh, scp etc. for a server which keeps changing IP every couple weeks (and our IT has a couple weeks delay in setting the host). I solved it using a special variable for this server: export FOO='131.227.aaa.bbb and then I can do just ssh bar@$FOO and I change the IP in my ~/.bashrc any time it changes...

tmow · Answer 9 · 2011-02-04T13:35:06.510

-2

Unlucky not, you cannot, except you write your own internet browser.

If you have to do some tests you need a test machine, whatever is a virtual machine or a real one, so you have to ask your Unix admin (or hosting provider) how you can put in place a development environment.

You can also install a VM on your PC, install a Linux distribution, Apache and test your changes (it's not as hard as it sounds)

Update

To better explain, each application is written using the standard libraries, this way nobody has to rewrite the low level library and functions like the gethostbyname().

These functions normally are set to use file (/etc/hosts) and DNS, so, unlucky, if you need that your browser will resolve a name than the one is set in the /etc/hosts you don't have too many alternatives.

You can set up your own DNS server and ask who has root rights to change the /etc/resolve.conf
You can install a proxy server like DeleGate and set some rules for your VirtualHost
Ask sudo rights on that customer host
Change the behavior of the application you are using to test the connection (I guess the browser), for example https://addons.mozilla.org/en-US/firefox/addon/switchhosts/

edited Feb 04 '11 at 13:35

answered Feb 04 '11 at 08:53

tmow

1,255

4

-1 worded poorly and patronizing. I AM the hosting provider, and it's the damn customers site on our server that I need to test. We have a network boot linux that I do not have admin access to, and I don't believe I can boot a VM on it. – xenoterracide Feb 04 '11 at 10:01
@xenoterracide there is not too much to say. It's really not feasible what you are asking for, except you change the way a SOCKET is created. – tmow Feb 04 '11 at 13:01
1

@xenoterracide BTW, there wasn't any intention to offend. – tmow Feb 04 '11 at 13:08
well as the hosting provider... I have "sudo rights" actually, I have real root on every box, and full access to everything... except my desktop (eyeroll) but if they haven't wanted to change their nameservers yet.. I can't help that... – xenoterracide Feb 06 '11 at 05:02
1

with LD_PRELOAD you can 'override' specific 'low level' functions and do what you want, eg. telling the program about your own '/etc/hosts' on open() and any other low level call .. as long as dynamic loading of code is invovled (.so) – akira Feb 06 '11 at 05:34

Can I create override dns similar to writing in /etc/hosts without root access

9 Answers9