How do I set up cron to run a file just once at a specific time? [closed]

Answer 1

For those who is not able to access/install at in environment, can use custom script:

#!/bin/bash
if [ $# -lt 2 ]; then
echo ""
echo "Syntax Error!"
echo "Usage: $0  "
echo " format: %Y%m%d%H%M"
echo "Example: $0 /home/user/scripts/server_backup.sh 202008142350"
echo ""
exit 1
fi

while true; do
  t=$(date +%Y%m%d%H%M);      
  if [ $t -eq $2 ]; then
    /bin/bash $1
    echo DONE $(date);
    break;
  fi;
  sleep 1;
done

Let's name the script as run1time.sh Example could be something like:

nohup bash run1time.sh /path/to/your/script.sh 202008150300 &