Thursday, October 13, 2022

SSH Setup (on two Ubuntu machines), Error Messages and Resolution 

System 1: ashishlaptop


(base) ashish@ashish-Lenovo-ideapad-130-15IKB:~$ ifconfig

enp1s0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 9c:5a:44:09:35:ee  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 375  bytes 45116 (45.1 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 375  bytes 45116 (45.1 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp2s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.131  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::5154:e768:24e1:aece  prefixlen 64  scopeid 0x20<link>
        inet6 2401:4900:47f6:d7d1:b724:d299:1a51:567  prefixlen 64  scopeid 0x0<global>
        inet6 2401:4900:47f6:d7d1:239a:fc2d:c994:6e54  prefixlen 64  scopeid 0x0<global>
        ether b0:fc:36:e5:ad:11  txqueuelen 1000  (Ethernet)
        RX packets 7899  bytes 8775440 (8.7 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 5299  bytes 665165 (665.1 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

(base) ashish@ashish-Lenovo-ideapad-130-15IKB:~$ hostname
ashish-Lenovo-ideapad-130-15IKB


To Change The Hostname


(base) ashish@ashish-Lenovo-ideapad-130-15IKB:~$ sudo nano /etc/hostname
(base) ashish@ashish-Lenovo-ideapad-130-15IKB:~$ cat /etc/hostname
ashishlaptop


System restart required at this point for new hostname to reflect everywhere.



To Setup Addressing of Connected Nodes and Their IP Addresses



Original File Contents



(base) ashish@ashishlaptop:~$ cat /etc/hosts
127.0.0.1	localhost
127.0.1.1	ashish-Lenovo-ideapad-130-15IKB

# 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


File "/etc/hosts" After Change


(base) ashish@ashishlaptop:~$ sudo nano /etc/hosts
(base) ashish@ashishlaptop:~$ cat /etc/hosts
192.168.1.131	ashishlaptop
192.168.1.106	ashishdesktop


Checking Connectivity With The Other Machine


(base) ashish@ashishlaptop:~$ ping 192.168.1.106


PING 192.168.1.106 (192.168.1.106) 56(84) bytes of data.
64 bytes from 192.168.1.106: icmp_seq=1 ttl=64 time=5.51 ms
64 bytes from 192.168.1.106: icmp_seq=2 ttl=64 time=115 ms
64 bytes from 192.168.1.106: icmp_seq=3 ttl=64 time=4.61 ms
64 bytes from 192.168.1.106: icmp_seq=4 ttl=64 time=362 ms
64 bytes from 192.168.1.106: icmp_seq=5 ttl=64 time=179 ms
64 bytes from 192.168.1.106: icmp_seq=6 ttl=64 time=4.53 ms
^C
--- 192.168.1.106 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5012ms
rtt min/avg/max/mdev = 4.525/111.739/361.954/129.976 ms 


System 2: ashishdesktop


(base) ashish@ashishdesktop:~$ ifconfig

ens33: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 00:e0:4c:3c:16:6b  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 317  bytes 33529 (33.5 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 317  bytes 33529 (33.5 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlx00e02d420fcb: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.106  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 2401:4900:47f6:d7d1:3cc9:20f6:af75:bb28  prefixlen 64  scopeid 0x0<global>
        inet6 2401:4900:47f6:d7d1:73e6:fca0:4452:382  prefixlen 64  scopeid 0x0<global>
        inet6 fe80::1cdd:53e7:d13a:4f52  prefixlen 64  scopeid 0x20<link>
        ether 00:e0:2d:42:0f:cb  txqueuelen 1000  (Ethernet)
        RX packets 42484  bytes 56651709 (56.6 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 28763  bytes 3324595 (3.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

(base) ashish@ashishdesktop:~$ hostname
ashishdesktop


Original Contents of File "/etc/hosts"



(base) ashish@ashishdesktop:~$ cat /etc/hosts
127.0.0.1	localhost
127.0.1.1	ashishdesktop

# 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



Modified Contents of "/etc/hosts"


(base) ashish@ashishdesktop:~$ sudo nano /etc/hosts
(base) ashish@ashishdesktop:~$ cat /etc/hosts
192.168.1.106	ashishdesktop
192.168.1.131	ashishlaptop



SSH Commands



First: Follow steps 1 to 7 on every node.

1) sudo apt-get install openssh-server openssh-client
2) sudo iptables -A INPUT -p tcp --dport ssh -j ACCEPT
3) Use the network adapter 'NAT' in the Guest OS settings, and create a new port forwarding rule "SSH" for port 22.
4) sudo reboot
5) ssh-keygen -t rsa -f ~/.ssh/id_rsa -P ""
6) sudo service ssh stop
7) sudo service ssh start


Second: After 'First' is done, follow steps 8 to 10 on every node. 

8) ssh-copy-id -i ~/.ssh/id_rsa.pub ashish@master
9) ssh-copy-id -i ~/.ssh/id_rsa.pub ashish@slave1
10) ssh-copy-id -i ~/.ssh/id_rsa.pub ashish@slave2


Error Messages And Resolutions



Error 1: Port 22: Connection refused



(base) ashish@ashishlaptop:~$ ssh-copy-id -i ~/.ssh/id_rsa.pub ashish@ashishdesktop
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ashish/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed

/usr/bin/ssh-copy-id: ERROR: ssh: connect to host ashishdesktop port 22: Connection refused


Resolution


First follow SSH steps 1 to 7 on both the machines.


Error 2: Could not resolve hostname ashishlaptop


(base) ashish@ashishdesktop:~$ ssh-copy-id -i ~/.ssh/id_rsa.pub ashish@ashishlaptop
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/ashish/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed

/usr/bin/ssh-copy-id: ERROR: ssh: Could not resolve hostname ashishlaptop: Temporary failure in name resolution


Resolution


Modify contents of two files "/etc/hostname" and "/etc/hosts" as shown above as the starting activity for this task.
Tags: Technology,Linux,SSH,
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