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?
20 Answers
Two things to check (assuming your machine is called my-machine, you can change this as appropriate):
That the
/etc/hostnamefile contains just the name of the machine.That
/etc/hostshas an entry forlocalhost. 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.
answered Sep 1, 2011 at 3:26
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45The 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.– YashvitMay 5, 2013 at 15:22
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2Note: 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) ALLto%admin ALL=NOPASSWD: ALL, then reboot, and sudo su -, edit those files, set/correct hostname, reboot again, and everything worked.– Ian MJul 17, 2016 at 20:19 -
4I'm using Linux Subsystem in Windows and I faced this problem. After following your answer, It has been resolved. Dec 28, 2016 at 15:43
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2you may also need to add
::1 localhostto/etc/hosts(this is the IPv6 version of 127.0.0.1, aka the loopback address) Sep 27, 2017 at 14:51 -
22Why does your example have
127.0.0.1 localhostbut127.0.1.1 my-machine?– AdamDec 21, 2017 at 23:11
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.
answered Apr 7, 2012 at 13:39
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4How can he edit the /etc/hosts file if he can't sudo? Unless he created a rood account with a password (bad idea)– DennisMar 29, 2015 at 22:31
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12@Dennis You can still execute
sudoeven 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. Mar 29, 2015 at 23:31 -
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as a debian user, there is no gksudo or gksu, i had to resort to using sed: step 1. run
touch myscriptstep 2. edit "myscript" (you can do this without sudo most of the time) and insertsed -i 's/127.0.0.1 localhost/127.0.0.1 localhost NEWHOSTHERE/' /etc/hostsstep 3.sudo bash myscript. Please note the tabs are there on purpose because it searches for127.0.0.1 localhostto be replaced with127.0.0.1 localhost NEWHOSTHERE.– petrosmmAug 27, 2020 at 20:35
Add your hostname to /etc/hosts like so:
echo $(hostname -I | cut -d\ -f1) $(hostname) | sudo tee -a /etc/hosts
answered Sep 15, 2014 at 16:03
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9It's clever, but I don't think it tends to be a good idea to automate something like this. Jan 4, 2018 at 13:59
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1This 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. Sep 21, 2018 at 21:05
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3this 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/hostsJan 7, 2019 at 11:31 -
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.
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11Remember! Use
sudoedit(orsudo -e). To specify preferred editor, use theEDITORenvironment variable (eg.export EDITOR=vim) as it creates an offline copy for editing and then cleanly overwrites after editing.– JanSep 26, 2014 at 13:54 -
2And there is another one here who suggest
sudowhen there is no longersudo.sudodoesn't work, sir.sudo: unable to resolve host ...– GreenJul 12, 2016 at 20:18 -
@Green: No
sudo? The error message you mention comes from thesudocommand. Perhaps you meant something different?– ThorJul 14, 2016 at 13:49 -
@Green
sudoworks just fine. It just can't store any state (i.e. as Lekensteyn said elsewhere you have to enter your password every time).– WlerinJul 28, 2016 at 19:16 -
4If 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.– aveAug 5, 2016 at 2:13
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 1, 2013 at 1:18
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2Also, see if your device name (printed on the Terminal title bar after the @ sign) matches the name on the second line of the
hostsfile ("ubuntu" in Luca's example). The first line may also be just "localhost". Oct 26, 2013 at 14:33 -
2Remember! Use
sudoedit(orsudo -e). To specify preferred editor, use theEDITORenvironment variable (eg.export EDITOR=vim) as it creates an offline copy for editing and then cleanly overwrites after editing.– JanSep 26, 2014 at 13:55 -
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.
In AWS, go to your vpc and turn on "DNS Hostnames".
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2Welcome to askubuntu! Can you expand a bit on this? It's not abundantly clear what you mean (at least to me).. Jan 15, 2015 at 13:56
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2This 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. Jul 1, 2015 at 1:16
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1the Enable DNS Hostnames option can be found (for example) in the right-click menu of the vpc entry Jan 3, 2016 at 17:32
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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. Sep 4, 2022 at 9:28
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.
answered Sep 18, 2017 at 22:17
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2
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This is interesting: Bash hangs in Linux subsystem in Windows 10 May 11, 2020 at 22:51
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'
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."
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.
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1The issue isn't the terminal emulators, it's the shells that have cached the value. Feb 16, 2017 at 19:53
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
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, 2011 at 19:16
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-nportion, rebooted and everything was fine.
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
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.
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5The root password in Ubuntu is not the same password for
sudo.rootis its own account, which doesn't have a password set by default. Aug 24, 2016 at 19:38
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!
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.
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
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2How can you edit
/etc/hostswithoutsudo.sudodoesn't worksudo: unable to resolve host ...– GreenJul 12, 2016 at 20:02
If you are using Vagrant, then login into the guest and run
apt-get --no-install-recommends install virtualbox-guest-utils
/etc/hostnameand/etc/hosts.hostsfile 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.hostnamesame withhosts. e.g. the hostname is ubuntu-pc and hosts is ubuntu-pc must be same.sudo /etc/init.d/network-manager restart. However, I'm wondering why in the first placesudowastes time waiting for network-related stuff. Shouldn'tsudowork without problems when network is not available?