05. Remote Access - some exercises for ssh and parallel-ssh
Chapter 5 gives some examples for ssh and parallel-ssh (pssh...). As a note, in Debian/Ubuntu etc. pssh etc. has been renamed to:
I have 5 VMs running on my PC - master, worker1...worker4. The workers are Ubuntu 18.04 servers, so they use the /etc/netplan/...yaml file for network configuration. I had already manually configured all of them, except for the ~/.ssh/config file.
I created a ~/.ssh/config file on the host with the following content:
Host master HostName 192.168.0.130 User student Host worker1 HostName 192.168.0.131 User student Host worker2 HostName 192.168.0.132 User student Host worker3 HostName 192.168.0.133 User student Host worker4 HostName 192.168.0.134 User student
I then ran the following script as an exercise:
#!/bin/bash # Exercise using parallel-scp and parallel-ssh # # ips.txt contains the IP addresses of the hosts, one per line # -h hostfile -- provides list of hosts (IP addresses) # -i inline -- print output inline on localhost # # This script does the following: # 1. Copies the ~.ssh/config file on LOCALHOST to the remote hosts # specified in ips.txt. # 2. Shows the remote config files using cat. # 3. Deletes the remote config files. # 4. Shows the remote config files using cat - this gives an error. # 5. Copies again the ~.ssh/config file on LOCALHOST to the remote hosts. # 6. Shows the remote config files using cat. parallel-scp -h ips.txt ~/.ssh/config /home/heiko/.ssh/ parallel-ssh -ih ips.txt cat ~/.ssh/config parallel-ssh -ih ips.txt rm ~/.ssh/config parallel-ssh -ih ips.txt cat ~/.ssh/config parallel-scp -h ips.txt ~/.ssh/config /home/heiko/.ssh/ parallel-ssh -ih ips.txt cat ~/.ssh/config
Since I already defined aliases for all my VMs, I could also use the aliases inside ips.txt:
worker1 worker2 worker3 worker4
The following is an exercise using parallel-slurp to copy remote files to the local host under ~/outdir:
#!/bin/bash # # Copy /etc/netplan/0....yaml files on remote hosts to local host: parallel-slurp -L ~/outdir -h remhosts.txt /etc/netplan/0* . # Copy the /etc/hosts and /etc/hostname files to local host: parallel-slurp -L ~/outdir -h remhosts.txt /etc/hosts . parallel-slurp -L ~/outdir -h remhosts.txt /etc/hostname .
Using the aliases, these files are then neatly stored in folders worker1...worker4.
I wonder if I could use pscp / parallel-scp to copy configuration stanzas to remote hosts and then manually change e.g. the IP. I'm talking specifically about the /etc/netplan/...yaml config file where I would have to change just the IP.
If I understand correctly, the IP would only change with the "netplan apply" command?