jumphost.md

ssh host:

create jumpy user, for that user, create a keypair, private key goes in the contest image(group_vars/all)

root@jumpbox:~# useradd -m -U -s /bin/bash jumpy
ssh-keygen -t ed25519 -f jumpbox_key

public key goes in the authorized_keys file for the jumpy user: command="echo 'This account can only be used for opening a reverse tunnel.'",no-agent-forwarding,no-X11-forwarding ssh-ed25519 SSH_PUBKEY jumpy@ssh.yourserver.com

Now generate a second key, this will be used to actually ssh into the machines as root, and needs to be kept private/secret

ssh-keygen -t ed25519 -f ~/.ssh/id_ed25519

Make sure the jumpbox listens on port 443 for ssh connections as wel

install parallel-ssh sudo apt-get update && sudo apt-get install pssh create discover-hosts.sh file with contents:

#!/bin/bash
set -euo pipefail

echo -n "" > ~/.ssh/config
PORTS=$(sudo lsof -i4TCP -sTCP:LISTEN -P -n | sed -r 's/.*:([0-9]+).*/\1/' | tail -n +2 )
idx=0
for p in $PORTS; do
  let idx=idx+1
  # Skip localhost
  if [[ $p == 443 || $p == 22 ]]; then continue; fi
  TEAM=$(ssh localhost -p $p -i ~/.ssh/id_ed25519 -l root -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no cat /icpc/TEAM 2>/dev/null| sed 's/team//')
  if [[ -z $TEAM ]]; then
    HOST=unknown-$idx
  else
    HOST=t$TEAM
  fi
  echo "$HOST - $p"
  cat >> ~/.ssh/config <<EOF
Host $HOST
    Hostname localhost
    Port $p
    User icpcadmin
    IdentityFile ~/.ssh/id_ed25519
EOF
done

edit bashrc, add the following alias:

tssh () { SSTART=$1; shift; SEND=$1; shift; declare -a SERVERS; HOSTS=($(grep -w -i "Host" /.ssh/config | sed 's/Host//')); for i in $(seq $SSTART $SEND); do if [[ " ${HOSTS[@]} " = " t$(printf %03d $i) " ]]; then SERVERS+=("-H t$(printf "%03d" $i)"); fi; done; echo -e "$ parallel-ssh \033[34m--timeout ${TIMEOUT:-10} --outdir /tmp/ \033[32m${SERVERS[@]} \033[31m$* \033[0m"; read -n 1 -p "Run it? [${#SERVERS[@]} servers] " doit; echo; case $doit in y | Y) parallel-ssh -O StrictHostKeyChecking=no --timeout ${TIMEOUT:-10} --outdir /tmp/ ${SERVERS[@]} $* ;; *) return ;; esac }

Run discover-hosts.sh once things are booted. Then you can use tssh 0 100 command to run a command across teams 0 to team 100.