Error message "sudo: unable to resolve host (none)"

Question

When I run sudo the terminal is stuck for a few seconds and then outputs an error message. My terminal looks like this:

ubuntu@(none):~$ sudo true
sudo: unable to resolve host (none)

What can I do to solve it?

Please post the contents of /etc/hostname and /etc/hosts. — arrange, Aug 31 '11 at 20:24
I recommend against closing this question as too localized. There are many users who may mistakenly think they've put one name in their hosts file but put in a different name instead, especially since on many networks, computers are similarly named. This question (and answer) would show up when someone searches with that problem, and the answer would prompt them to check for such discrepancies, even though the exact misspelling would be different. — Eliah Kagan, Aug 18 '12 at 11:09
make sure your hostname same with hosts. e.g. the hostname is ubuntu-pc and hosts is ubuntu-pc must be same. — Muhammad Sholihin, Apr 01 '13 at 08:17
I ran into this today. The problem was that what I had in hostname wasn't in /etc/hosts. To wit: $ hostname => 'mybox' $ grep 'mybox' /etc/hosts => 192.168.1.2 mybox.example.com. I needed to add 'mybox' after my domain name in /etc/hosts => 192.168.1.2 mybox.example.com mybox — Jim, Mar 25 '17 at 21:16
I can't post an answer because this question is protected and I don't have enough reputation here. In my case, I solved the problem by restarting network-manager: sudo /etc/init.d/network-manager restart. However, I'm wondering why in the first place sudo wastes time waiting for network-related stuff. Shouldn't sudo work without problems when network is not available? — bli, Jul 31 '17 at 08:45
Why does the question have <USER> at the end? This contradicts the actual output shown in the body of the question as (none) Suggestion for improvement: remove <USER> from title and/or replace it with (none) — arielf, Dec 14 '18 at 21:32
@arielf You can improve questions on here. It was changed by another user. I don't know either. :P — Kit Sunde, Dec 16 '18 at 08:46

score 1299 · Accepted Answer · edited Dec 22 '16 at 00:23

1299

Two things to check (assuming your machine is called my-machine, you can change this as appropriate):

That the /etc/hostname file contains just the name of the machine.

That /etc/hosts has an entry for localhost. It should have something like:

 127.0.0.1    localhost.localdomain localhost
 127.0.1.1    my-machine

If either of these files aren't correct (since you can't sudo), you may have to reboot the machine into recovery mode and make the modifications, then reboot to your usual environment.

edited Dec 22 '16 at 00:23

Thomas Ward

74,764

answered Sep 01 '11 at 03:26

Jeremy Kerr

27,199

46

The hostname will not change until you reboot. If you wish to change it without rebooting the machine then follow the above steps and after that run:- "sudo hostname my-machine" to see if this has worked run "sudo hostname" It will show your machine's host name. This method maybe used as a temporary method to change hostname also. after a restart, the value from the /etc/hostname file is used. – Yashvit May 05 '13 at 15:22
2

Note: since you can't sudo to begin with, it is difficult to edit those files. My solution was I was somehow able to sudo visudo and change #%admin ALL=(ALL) ALL to %admin ALL=NOPASSWD: ALL , then reboot, and sudo su -, edit those files, set/correct hostname, reboot again, and everything worked. – Ian M Jul 17 '16 at 20:19
4

I'm using Linux Subsystem in Windows and I faced this problem. After following your answer, It has been resolved. – amarVashishth Dec 28 '16 at 15:43
@amarVashishth can you list the steps taken? I am facing the same problem. I tried what the answer tells to do but failed – Meet Taraviya Feb 03 '17 at 12:08
@MeetTaraviya I followed same steps as he told. It worked for me. – amarVashishth Feb 03 '17 at 13:42
@amarVashishth "reboot the machine into recovery mode" . Does that mean the actual pc or just the linux subsystem? – Meet Taraviya Feb 03 '17 at 15:12
doesn't work, now I can't TV into my server – wayofthefuture Sep 05 '17 at 19:54
3

you may also need to add ::1 localhost to /etc/hosts (this is the IPv6 version of 127.0.0.1, aka the loopback address) – Woodrow Barlow Sep 27 '17 at 14:51
It worked for me with sudo gedit /etc/hosts, then changing and saving the file. – Shamim Oct 03 '17 at 16:47
@MeetTaraviya I just skipped the reboot step. For WSL (Windows Linux Subsystem) it is enough to just edit /etc/hosts. Note that you have to replace my-machine with the host name from the error message on your computer. – ossbuntu Nov 10 '17 at 10:58
22

Why does your example have 127.0.0.1 localhost but 127.0.1.1 my-machine? – Adam Dec 21 '17 at 23:11
2

in my case the reason was that hostnamectl set-hostname ... change /etc/hostname but no /etc/hosts. – Pablo Bianchi Jan 31 '19 at 03:40
good find. Now I wonder if a bug should be reported against gnome-settings, because that's where I changed by hostname after moving disks... – Vincent Gerris Apr 06 '20 at 11:44
Do you really, really use 127.0.1.1 and not 127.0.0.1 for the new hostname? Just asking because the second highest rated answer only uses 127.0.0.1, and 127.0.1.1 doesn't work for me. – crobar Jun 03 '20 at 10:05
@crobar: yep, that's what I have; 127.0.0.1 for localhost, and 127.0.1.1 for the hostname. – Jeremy Kerr Jun 05 '20 at 04:06
@JeremyKerr thanks, actually it wasn't working for me because of a setting in nsswitch.conf i can confirm it does work for me now with 127.0.1.1 – crobar Jun 05 '20 at 08:46
edit the /etc/hostname file and make sure it has only the name provided at cat hostname. Then make sure this name is the same even in /etc/hosts. It worked for me just fine! – NMukama Jan 22 '21 at 11:19
This question does not define what "my-machine" means or how to even get that value. Rated down till resolved. My assumption is /etc/hostname will output "my-machine", but I cannot be certain. – Matthaeus Gaius Caesar Mar 29 '22 at 22:50

score 248 · Answer 2 · edited Apr 13 '17 at 12:24

248

Edit /etc/hosts and append your new hostname to the 127.0.0.1 line (or create a new line if you prefer that).

Mine looks like:

127.0.0.1       localhost localhost.localdomain penguin

# The following lines are desirable for IPv6 capable hosts
::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

Replace penguin in the above example by your new hostname as stated in the /etc/hostname file.

edited Apr 13 '17 at 12:24

Community

1

answered Apr 07 '12 at 13:39

Lekensteyn

174,277

4

How can he edit the /etc/hosts file if he can't sudo? Unless he created a rood account with a password (bad idea) – Dennis Mar 29 '15 at 22:31
12

@Dennis You can still execute sudo even if that message is displayed. IIRC you still have to enter your password at each invocation though. If this does not work, you can reboot into the recovery console and apply the changes. A root account with password is discouraged. – Lekensteyn Mar 29 '15 at 23:31
helpful answer. – Bonn Jun 27 '20 at 07:25
as a debian user, there is no gksudo or gksu, i had to resort to using sed: step 1. run touch myscript step 2. edit "myscript" (you can do this without sudo most of the time) and insert sed -i 's/127.0.0.1 localhost/127.0.0.1 localhost NEWHOSTHERE/' /etc/hosts step 3. sudo bash myscript. Please note the tabs are there on purpose because it searches for 127.0.0.1 localhost to be replaced with 127.0.0.1 localhost NEWHOSTHERE. – petrosmm Aug 27 '20 at 20:35

score 91 · Answer 3 · answered Sep 15 '14 at 16:03

91

Add your hostname to /etc/hosts like so:

echo $(hostname -I | cut -d\  -f1) $(hostname) | sudo tee -a /etc/hosts

answered Sep 15 '14 at 16:03

Collin Anderson

3,206

9

It's clever, but I don't think it tends to be a good idea to automate something like this. – mwfearnley Jan 04 '18 at 13:59
1

This does an append of the hostname to the hosts file. There is an inherent assumption that there is nothing in between the loopback ip the mapping to localhost and end of file, but there is now some IPv6 stuff between this line and end of file, in which case this solution does not really end up giving you what you would want. A related comment: Editing this or other files requires use of sudo and it is sudo that we are trying to fix. We still need to be able to run sudo. In this case sudo -h hostname can be used to first change permissions on the files or gain the elevation to edit them. – shivesh suman Sep 21 '18 at 21:05
3

this fails because I can't "sudo tee.." but this did the trick:
echo $(hostname -I | cut -d\ -f1) $(hostname) | sudo -h 127.0.0.1 tee -a /etc/hosts
– Ronny Elflein r11lein Jan 07 '19 at 11:31
working completely fine – code by Abhishek Bharti Feb 12 '23 at 14:45

score 38 · Answer 4 · edited Apr 13 '17 at 12:23

38

Note, this is an answer to this question which has been merged with this one.

Your hostname (dave00-G31M-ES2L) is not represented in /etc/hosts. Add an L to this line:

127.0.1.1   dave00-G31M-ES2

So it becomes:

127.0.1.1   dave00-G31M-ES2L

In order to accomplish this, open a console (press Ctrl+Alt+T) and type:

sudo gedit /etc/hosts

Add the letter L as mentioned, save and exit.

edited Apr 13 '17 at 12:23

Community

1

answered Aug 18 '12 at 11:02

Thor

3,578

11

Remember! Use sudoedit (or sudo -e). To specify preferred editor, use the EDITOR environment variable (eg. export EDITOR=vim) as it creates an offline copy for editing and then cleanly overwrites after editing. – Jan Sep 26 '14 at 13:54
2

And there is another one here who suggest sudo when there is no longer sudo. sudo doesn't work, sir. sudo: unable to resolve host ... – Green Jul 12 '16 at 20:18
@Green: No sudo? The error message you mention comes from the sudo command. Perhaps you meant something different? – Thor Jul 14 '16 at 13:49
@Green sudo works just fine. It just can't store any state (i.e. as Lekensteyn said elsewhere you have to enter your password every time). – Wlerin Jul 28 '16 at 19:16
4

If you have this issue on W10's Bash and came to this question from google, this is the answer that worked for me. I changed the 127.0.0.1 to look like "127.0.0.1 localhost DESKTOP-SLQK4CV" (by doing "sudo vim /etc/hosts" (quick tip for vim newbies: press i before typing to switch to insert mode, press esc to exit that, write ":wq" to save and exit or ":q!" to exit without saving), in my case sudo worked but just said that it can't connect to DESKTOP-SLQK4CV) and it started worked for me. – ave Aug 05 '16 at 02:13

score 20 · Answer 5 · answered Apr 01 '13 at 01:18

20

I had this issue when I was using ubuntu on a VPS. I solved it editing /etc/hosts file.

run this command:

sudo nano /etc/hosts

and then add:

127.0.0.1   localhost.localdomain localhost
127.0.1.1   ubuntu

I hope that will solve your issue :)

PS: Remember to reboot your computer!

answered Apr 01 '13 at 01:18

Luca D'Amico

554

2

Also, see if your device name (printed on the Terminal title bar after the @ sign) matches the name on the second line of the hosts file ("ubuntu" in Luca's example). The first line may also be just "localhost". – Waldir Leoncio Oct 26 '13 at 14:33
2

Remember! Use sudoedit (or sudo -e). To specify preferred editor, use the EDITOR environment variable (eg. export EDITOR=vim) as it creates an offline copy for editing and then cleanly overwrites after editing. – Jan Sep 26 '14 at 13:55
Isn't this answer essentially the same as this older one? – Dan Dascalescu Jun 29 '20 at 10:20

score 14 · Answer 6 · answered Aug 13 '14 at 13:50

I was having the same issue even though the hostname in my /etc/hostname file and /etc/hosts file matched.

My hostname was "staging_1". It turns out that you can't have an underscore in your hostname, which is why I was getting this error. Changing the underscore to a hyphen fixed my problem.

score 12 · Answer 7 · answered Jan 15 '15 at 05:15

12

In AWS, go to your vpc and turn on "DNS Hostnames".

answered Jan 15 '15 at 05:15

Erick

137
1
2

2

Welcome to askubuntu! Can you expand a bit on this? It's not abundantly clear what you mean (at least to me).. – Elder Geek Jan 15 '15 at 13:56
2

This was the answer that helped me. Amazon AWS changed since the last time I looked at it. VPCs have DNS options, and they need to be turned on before any DNS resolution will work. – Chris Moore Jul 01 '15 at 01:16
1

the Enable DNS Hostnames option can be found (for example) in the right-click menu of the vpc entry – Matteo Scotuzzi Jan 03 '16 at 17:32
There is no DNS Hostnames – Green Jul 12 '16 at 20:11
Similar issue occurred on Azure for me when I changed the default DNS servers in the VNet. I fixed it by adding my current hostname to the hosts file using sudo --host 127.0.0.1 vi /etc/hosts, as suggested in other answers. – ManSamVampire Sep 04 '22 at 09:28

score 10 · Answer 8 · answered Jul 28 '18 at 17:24

Everybody advises to modify /etc/hosts. But in some cases this may not be possible (for example inside a docker container). So, I had to find a better way and I came up with this:

echo "alias sudo='sudo -h 127.0.0.1'" >> ~/.bash_aliases
source ~/.bashrc

Aliases don't work in bash scripts, but we can use variables: sudo='sudo -h 127.0.0.1'

Brent Bradburn · Answer 9 · 2017-09-18T22:23:24.730

10

The symptom given in the question may correlate strongly with this more specific problem:

$ hostname --fqdn
hostname: Temporary failure in name resolution

There are different ways that this could be resolved, one of which is to add your hostname as localhost in /etc/hosts (as shown in several other answers). This may be the right thing to do in general, but it isn't the only possible resolution.

A "fully qualified domain name" may be supplied by an external DNS server or similar (if such is available on your network). In this case, sudo will not complain, despite the missing entry in /etc/hosts.

Note: sudo attempts to dereference the hostname, even though it isn't necessarily required, due to optional capabilities in the sudoers file. See sudo command trying to search for hostname.

As long as the delay isn't too long, this error message is typically harmless.

edited Sep 18 '17 at 22:23

answered Sep 18 '17 at 22:17

Brent Bradburn

2,836

2

Somewhat faster: sudo --host=localhost – Brent Bradburn Apr 15 '19 at 23:50
Upvote for the sudo command trying to search for hostname link – x-yuri Oct 02 '19 at 16:43
This is interesting: Bash hangs in Linux subsystem in Windows 10 – Brent Bradburn May 11 '20 at 22:51

score 6 · Answer 10 · answered Feb 13 '16 at 11:44

I encountered this same error message. I think this discussion thread at AWS Developer Forums is a better solution:

"Go the the VPC management console, select the VPC, click on Actions, select Edit DNS Hostnames and select Yes."

https://forums.aws.amazon.com/thread.jspa?messageID=699718

score 6 · Answer 11 · answered Jun 19 '16 at 16:29

6

Some terminal emulators will not update prompt with the correct hostname until you close and restart the emulator (lxterminal, I'm talking to you).

I spent 30min fighting with this error after editing my hostname and hosts files and running sudo service hostname restart until I ran sudo hostname and saw that the hostname was the new value, even though the prompt was showning the old value.

answered Jun 19 '16 at 16:29

dagbel

61

1

The issue isn't the terminal emulators, it's the shells that have cached the value. – Mark Stosberg Feb 16 '17 at 19:53

score 5 · Answer 12 · answered Jan 09 '14 at 22:24

In my case it was the problem, I changed the hostname to man because I wanted to know if there are some parameters you can use on hostname. Instead it changed my hostname to man and I always got the same message like you

sudo: unable to resolve host (none)

after changing the hostname back to `localhost everything worked fine again

hostname localhost

score 3 · Answer 13 · answered Aug 31 '11 at 19:16

3

Sorry I can't help you much but, since it says "can't resolve host" try running:

hostname

And see if the output is the hostname of the machine. If not, the problem is the host configuration, not sudo.

answered Aug 31 '11 at 19:16

animaletdesequia

8,354

I did that got the hostname of my machine. I also have entry in /etc/hosts. I'm still getting the error. – CKM May 06 '17 at 13:22
Did you reboot the machine after changing the hosts file? – animaletdesequia May 07 '17 at 18:52
No. Though my IT team said there was issue with lock file as well as gpg key with puppetlabs. Now, it got resolved without restart.. – CKM May 08 '17 at 09:28

score 2 · Answer 14 · answered May 21 '19 at 06:45

In case your problem is that /etc/hostname file and /etc/hosts, both files have your desired hostname and still your machine is showing the error

sudo: unable to resolve host

Try, forcing the hostname

sudo hostname -F /etc/hostname

You will probably still get the same error, but try logging out and logging back in. It worked for me.

score 2 · Answer 15 · answered Apr 13 '14 at 05:19

OP wrote:

It was all in /etc/hostname. On two of our sick servers it looked like this:
ubuntu@(none):~$ cat /etc/hostname
linux-web-n ip-10-128-##-##
While on a server without this issue we had:
ubuntu@ip-10-128-##-###:~$ cat /etc/hostname
ip-10-128-##-###
Removed the linux-web-n portion, rebooted and everything was fine.

score 2 · Answer 16 · answered Jan 18 '15 at 03:26

2

you might be getting an error if your hosts or hostname file contain illegal characters. Only these symbols are permitted: a-z, A-Z, 0-9

answered Jan 18 '15 at 03:26

M.G.

121
2

score 2 · Answer 17 · answered Aug 24 '16 at 15:07

2

if you can't sudo you CAN log in as root via su. IE: su root (in an x-term). then give the root password when prompted, then you can edit the files with nano. The root password in 'buntu is the same as the password you would use for sudo.

answered Aug 24 '16 at 15:07

ken scharf

21

5

The root password in Ubuntu is not the same password for sudo. root is its own account, which doesn't have a password set by default. – TheWanderer Aug 24 '16 at 19:38

score 2 · Answer 18 · answered Jan 10 '17 at 02:18

I had this same problem! I changed my VPS's name through the online admin control panel which did not change the machine name in the hosts file All I did was run:

sudo nano /etc/hosts

Then I edited it from this:

127.0.1.1 Megabyte Megabyte
127.0.0.1 localhost

To this:

127.0.1.1 Debian Debian
127.0.0.1 localhost

and that fixed my error! Hope this helped!

score 1 · Answer 19 · edited Mar 26 '16 at 17:59

1

I had the same problem. I solved it by editing the /etc/hosts and /etc/hostname files... on the /etc/hosts file, just edit the top part as shown below.

#vi /etc/hosts
    127.0.0.1   localhost
    127.0.1.1   localhost  myhostname




#vi /etc/hostname
    myhostname

edited Mar 26 '16 at 17:59

muru

197,895
55
485
740

answered Mar 26 '16 at 17:53

Centy

21
1

127.0.1.1 localhost myhostname or 127.0.1.1 myhostname? – Mostafa Ahangarha Mar 26 '16 at 18:43
2

How can you edit /etc/hosts without sudo. sudo doesn't work sudo: unable to resolve host ... – Green Jul 12 '16 at 20:02

score 1 · Answer 20 · answered Jul 13 '17 at 07:27

1

If you are using Vagrant, then login into the guest and run apt-get --no-install-recommends install virtualbox-guest-utils

answered Jul 13 '17 at 07:27

tanmoy

101
1
4

Error message "sudo: unable to resolve host (none)"

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