Cannot SSH using hostname

[stii]

Hello.

I cannot SSH into machine using machine's hostname, but I can with IP address.

This is the output of nslookup hostname:

Server:        192.168.1.1
Address:    192.168.1.1#53

Name:    hostname
Address: 192.168.1.5
Name:    hostname
Address: 192.168.1.5

ping hostname:

ping: hostname: Name or service not known

And my resolv.conf:

# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
# 127.0.0.53 is the systemd-resolved stub resolver.
# run "systemd-resolve --status" to see details about the actual nameservers.

nameserver 192.168.1.1
nameserver fe80::1
nameserver 127.0.0.53

[TheFu]

If you can't ping by the name you want, then you haven't setup your network name resolution correctly. It isn't automatic.

There are 3 popular solutions.
1) modify the /etc/hosts on all the systems you want to know the IP -to- name mapping. This is what I use on my subnet. I use ansible to push updates for the hosts file out to all the systems here. We use ansible for many other solutions too.
2) use a DNS server, which you manually maintain on the network. Some routers can do this, but most require complex manual setups.
3) use avahi on all systems. This means using {hostname}.local as the name to ping/ssh/access.

IP networking doesn't include any automatic announcement that "I'm here, I'm here" like some other network protocols (smb/cifs) from other OSes do. Those broadcasts don't really scale beyond a tiny network and aren't part of the IP standards.

Welcome to the forums.

[stii]

If you can't ping by the name you want, then you haven't setup your network name resolution correctly. It isn't automatic.

There are 3 popular solutions.
1) modify the /etc/hosts on all the systems you want to know the IP -to- name mapping. This is what I use on my subnet. I use ansible to push updates for the hosts file out to all the systems here. We use ansible for many other solutions too.
2) use a DNS server, which you manually maintain on the network. Some routers can do this, but most require complex manual setups.
3) use avahi on all systems. This means using {hostname}.local as the name to ping/ssh/access.

IP networking doesn't include any automatic announcement that "I'm here, I'm here" like some other network protocols (smb/cifs) from other OSes do. Those broadcasts don't really scale beyond a tiny network and aren't part of the IP standards.

Welcome to the forums.

But the other PC (the one I am trying to SSH into) can SSH into this one with hostname, and can ping this one using hostname too. Both of them are on the same router. So (I think) I already have DNS server.

[SeijiSensei]

You're sure that 192.168.1.5 is the correct address for that host?

What if you add the entry

192.168.1.5     hostname

to /etc/hosts. (Use "sudo nano /etc/hosts" to edit the file if you've not modified system files like this before.) Now try to connect with ping and ssh. Any better? If not, I'd check the target's IP address again.

[stii]

You're sure that 192.168.1.5 is the correct address for that host?

What if you add the entry

192.168.1.5     hostname

to /etc/hosts. (Use "sudo nano /etc/hosts" to edit the file if you've not modified system files like this before.) Now try to connect with ping and ssh. Any better? If not, I'd check the target's IP address again.

192.168.1.5 is correct. After all, I can SSH into the machine with that IP.
Adding

192.168.1.5    hostname

to /etc/hosts does work, but I don't want to use that since IP changes sometimes (I use DHCP) so I have to change entry in /etc/hosts manually every time address changes. I know I don't need

192.168.1.5    hostname

in /etc/hosts because the other machine also doesn't have that entry for this machine but it always connects succesfully to this machine even when IP of this machine changes, only using hostname.

[TheFu]

Setup dhcp reservations on your network so that machines always get the same IP.
http://blog.jdpfu.com/2011/07/18/use...ice-management

Troubleshooting ssh: http://blog.jdpfu.com/2015/08/17/tro...sh-connections
* check the logs and
* up the debug "verbosity"
is basically what it says.

[stii]

I solved it. Here is where I found the solution: https://askubuntu.com/a/81807

[TheFu]

I solved it. Here is where I found the solution: https://askubuntu.com/a/81807

Happy that you found a solution - it would be helpful if you summarized which of the choices worked.

The more the "new kids" try to make things better, the more often they mess up the 40 yr old stuff that has been working all this time, just without as much automation. mdns is one of those things. resolvconf is another. Good intentions on both, but they don't handle all the old-school methods which are commonly deployed well at all.

IMHO.

[SeijiSensei]

I solved it. Here is where I found the solution: https://askubuntu.com/a/81807

I have no .local or any similar domain. I use the .com and .org domains that I control. Never would have guessed the problem lay where it did. Hosts do not need to belong to a domain, so the command "ssh hostname" is perfectly valid and need not be munged to "ssh hostname.local". I'm with TheFu on these kinds of "innovations."

[stii]

The link leads to the first chosen answer.