chroot0.sh is a bash script to create a custom sandbox based on chroot0.sh from book Core Kubernetes. Christopher Love, Jay Vyas. More information on https://www.manning.com/books/core-kubernetes

README.md

chroot0

chroot0.sh is a bash script to create a custom sandbox based on chroot0.sh from book Core Kubernetes. Christopher Love, Jay Vyas.

More information on https://www.manning.com/books/core-kubernetes

chroot0.sh

#!/bin/bash

### A bash script to create a custom sandbox based on chroot0.sh from book Core Kubernetes. Christopher Love, Jay Vyas
### https://www.manning.com/books/core-kubernetes

is_path_mounted() {
    local path_to_check="$1"

    # Get the list of mounted filesystems
    mounted_path=$(mount |grep "${path_to_check}" |awk '{print $3}')

    # Check if the specified path is in the list of mounted paths
    if [ "$mounted_path" = "$path_to_check" ]; then
       echo "The path $path_to_check is already mounted ($mounted_path)."
      return 0  # true
    fi

    echo "The path $path_to_check is not mounted ($mounted_path)."
    return 1  # false
}



if [ -z "$1" ]
then
  SANDBOX_PATH="/home/namespace/box"
else
  SANDBOX_PATH=$1
fi


echo "SANDBOX_PATH=${SANDBOX_PATH}"


creating_minimal_sandbox(){
  ### Creating sandbox
  local sbox_path=$1
  mkdir -p ${sbox_path} ${sbox_path}/bin ${sbox_path}/lib ${sbox_path}/lib64 ${sbox_path}/proc ${sbox_path}/data

  ### Customizing sandbox
  cp -v /usr/bin/kill /usr/bin/ps /usr/bin/grep /bin/bash /bin/ls ${sbox_path}/bin/

  ### Copying kernel libs
  CP_COMMAND="cp -v -r -p --reflink=auto --update"
  ${CP_COMMAND} /lib/* ${sbox_path}/lib/
  ${CP_COMMAND} /lib64/* ${sbox_path}/lib64/
}

mounting_volumes(){
  local sbox_path=$1
  ### Mounting proc
  if is_path_mounted "${sbox_path}/proc"
  then
    echo "Already mounted ${sbox_path}/proc"
  else
    echo "Mounting ${sbox_path}/proc"
    mount -t proc proc ${sbox_path}/proc
  fi

  ### Binding local tmp as data folder
  if is_path_mounted "${sbox_path}/data"
  then
    echo "Already mounted ${sbox_path}/data"
  else
    echo "Mounting ${sbox_path}/data"
    mount --bind /tmp/ ${sbox_path}/data
  fi
}

running_sandbox(){
  local sbox_path=$1
  chroot ${sbox_path} /bin/bash
}
main(){
  creating_minimal_sandbox "${SANDBOX_PATH}"
  mounting_volumes "${SANDBOX_PATH}"
  running_sandbox "${SANDBOX_PATH}"
}

main $@