逛github发现个有趣的项目：100行代码实现docker

    就这一个脚本

    1. #!/usr/bin/env bash
    2. set -o errexit -o nounset -o pipefail; shopt -s nullglob
    3. btrfs_path='/var/bocker' && cgroups='cpu,cpuacct,memory';
    4. [[ $# -gt 0 ]] && while [ "${1:0:2}" == '--' ]; do OPTION=${1:2}; [[ $OPTION =~ = ]] && declare "BOCKER_${OPTION/=*/}=${OPTION/*=/}" || declare "BOCKER_${OPTION}=x"; shift; done
    6. function bocker_check() {
    7.     btrfs subvolume list "$btrfs_path" | grep -qw "$1" && echo 0 || echo 1
    8. }
    10. function bocker_init() { #HELP Create an image from a directory:\nBOCKER init <directory>
    11.     uuid="img_$(shuf -i 42002-42254 -n 1)"
    12.     if [[ -d "$1" ]]; then
    13.         [[ "$(bocker_check "$uuid")" == 0 ]] && bocker_run "$@"
    14.         btrfs subvolume create "$btrfs_path/$uuid" > /dev/null
    15.         cp -rf --reflink=auto "$1"/* "$btrfs_path/$uuid" > /dev/null
    16.         [[ ! -f "$btrfs_path/$uuid"/img.source ]] && echo "$1" > "$btrfs_path/$uuid"/img.source
    17.         echo "Created: $uuid"
    18.     else
    19.         echo "No directory named '$1' exists"
    20.     fi
    21. }
    23. function bocker_pull() { #HELP Pull an image from Docker Hub:\nBOCKER pull <name> <tag>
    24.     token="$(curl -sL -o /dev/null -D- -H 'X-Docker-Token: true' "https://index.docker.io/v1/repositories/$1/images" | tr -d '\r' | awk -F ': *' '$1 == "X-Docker-Token" { print $2 }')"
    25.     registry='https://registry-1.docker.io/v1'
    26.     id="$(curl -sL -H "Authorization: Token $token" "$registry/repositories/$1/tags/$2" | sed 's/"//g')"
    27.     [[ "${#id}" -ne 64 ]] && echo "No image named '$1:$2' exists" && exit 1
    28.     ancestry="$(curl -sL -H "Authorization: Token $token" "$registry/images/$id/ancestry")"
    29.     IFS=',' && ancestry=(${ancestry//[\[\] \"]/}) && IFS=' \n\t'; tmp_uuid="$(uuidgen)" && mkdir /tmp/"$tmp_uuid"
    30.     for id in "${ancestry[@]}"; do
    31.         curl -#L -H "Authorization: Token $token" "$registry/images/$id/layer" -o /tmp/"$tmp_uuid"/layer.tar
    32.         tar xf /tmp/"$tmp_uuid"/layer.tar -C /tmp/"$tmp_uuid" && rm /tmp/"$tmp_uuid"/layer.tar
    33.     done
    34.     echo "$1:$2" > /tmp/"$tmp_uuid"/img.source
    35.     bocker_init /tmp/"$tmp_uuid" && rm -rf /tmp/"$tmp_uuid"
    36. }
    38. function bocker_rm() { #HELP Delete an image or container:\nBOCKER rm <image_id or container_id>
    39.     [[ "$(bocker_check "$1")" == 1 ]] && echo "No container named '$1' exists" && exit 1
    40.     btrfs subvolume delete "$btrfs_path/$1" > /dev/null
    41.     cgdelete -g "$cgroups:/$1" &> /dev/null || true
    42.     echo "Removed: $1"
    43. }
    45. function bocker_images() { #HELP List images:\nBOCKER images
    46.     echo -e "IMAGE_ID\t\tSOURCE"
    47.     for img in "$btrfs_path"/img_*; do
    48.         img=$(basename "$img")
    49.         echo -e "$img\t\t$(cat "$btrfs_path/$img/img.source")"
    50.     done
    51. }
    53. function bocker_ps() { #HELP List containers:\nBOCKER ps
    54.     echo -e "CONTAINER_ID\t\tCOMMAND"
    55.     for ps in "$btrfs_path"/ps_*; do
    56.         ps=$(basename "$ps")
    57.         echo -e "$ps\t\t$(cat "$btrfs_path/$ps/$ps.cmd")"
    58.     done
    59. }
    61. function bocker_run() { #HELP Create a container:\nBOCKER run <image_id> <command>
    62.     uuid="ps_$(shuf -i 42002-42254 -n 1)"
    63.     [[ "$(bocker_check "$1")" == 1 ]] && echo "No image named '$1' exists" && exit 1
    64.     [[ "$(bocker_check "$uuid")" == 0 ]] && echo "UUID conflict, retrying..." && bocker_run "$@" && return
    65.     cmd="${@:2}" && ip="$(echo "${uuid: -3}" | sed 's/0//g')" && mac="${uuid: -3:1}:${uuid: -2}"
    66.     ip link add dev veth0_"$uuid" type veth peer name veth1_"$uuid"
    67.     ip link set dev veth0_"$uuid" up
    68.     ip link set veth0_"$uuid" master bridge0
    69.     ip netns add netns_"$uuid"
    70.     ip link set veth1_"$uuid" netns netns_"$uuid"
    71.     ip netns exec netns_"$uuid" ip link set dev lo up
    72.     ip netns exec netns_"$uuid" ip link set veth1_"$uuid" address 02:42:ac:11:00"$mac"
    73.     ip netns exec netns_"$uuid" ip addr add 10.0.0."$ip"/24 dev veth1_"$uuid"
    74.     ip netns exec netns_"$uuid" ip link set dev veth1_"$uuid" up
    75.     ip netns exec netns_"$uuid" ip route add default via 10.0.0.1
    76.     btrfs subvolume snapshot "$btrfs_path/$1" "$btrfs_path/$uuid" > /dev/null
    77.     echo 'nameserver 8.8.8.8' > "$btrfs_path/$uuid"/etc/resolv.conf
    78.     echo "$cmd" > "$btrfs_path/$uuid/$uuid.cmd"
    79.     cgcreate -g "$cgroups:/$uuid"
    80.     : "${BOCKER_CPU_SHARE:=512}" && cgset -r cpu.shares="$BOCKER_CPU_SHARE" "$uuid"
    81.     : "${BOCKER_MEM_LIMIT:=512}" && cgset -r memory.limit_in_bytes="$((BOCKER_MEM_LIMIT * 1000000))" "$uuid"
    82.     cgexec -g "$cgroups:$uuid" \
    83.         ip netns exec netns_"$uuid" \
    84.         unshare -fmuip --mount-proc \
    85.         chroot "$btrfs_path/$uuid" \
    86.         /bin/sh -c "/bin/mount -t proc proc /proc && $cmd" \
    87.         2>&1 | tee "$btrfs_path/$uuid/$uuid.log" || true
    88.     ip link del dev veth0_"$uuid"
    89.     ip netns del netns_"$uuid"
    90. }
    92. function bocker_exec() { #HELP Execute a command in a running container:\nBOCKER exec <container_id> <command>
    93.     [[ "$(bocker_check "$1")" == 1 ]] && echo "No container named '$1' exists" && exit 1
    94.     cid="$(ps o ppid,pid | grep "^$(ps o pid,cmd | grep -E "^\ *[0-9]+ unshare.*$1" | awk '{print $1}')" | awk '{print $2}')"
    95.     [[ ! "$cid" =~ ^\ *[0-9]+$ ]] && echo "Container '$1' exists but is not running" && exit 1
    96.     nsenter -t "$cid" -m -u -i -n -p chroot "$btrfs_path/$1" "${@:2}"
    97. }
    99. function bocker_logs() { #HELP View logs from a container:\nBOCKER logs <container_id>
    100.     [[ "$(bocker_check "$1")" == 1 ]] && echo "No container named '$1' exists" && exit 1
    101.     cat "$btrfs_path/$1/$1.log"
    102. }
    104. function bocker_commit() { #HELP Commit a container to an image:\nBOCKER commit <container_id> <image_id>
    105.     [[ "$(bocker_check "$1")" == 1 ]] && echo "No container named '$1' exists" && exit 1
    106.     [[ "$(bocker_check "$2")" == 1 ]] && echo "No image named '$2' exists" && exit 1
    107.     bocker_rm "$2" && btrfs subvolume snapshot "$btrfs_path/$1" "$btrfs_path/$2" > /dev/null
    108.     echo "Created: $2"
    109. }
    111. function bocker_help() { #HELP Display this message:\nBOCKER help
    112.     sed -n "s/^.*#HELP\\s//p;" < "$1" | sed "s/\\\\n/\n\t/g;s/$/\n/;s!BOCKER!${1/!/\\!}!g"
    113. }
    115. [[ -z "${1-}" ]] && bocker_help "$0"
    116. case $1 in
    117.     pull|init|rm|images|ps|run|exec|logs|commit) bocker_"$1" "${@:2}" ;;
    118.     *) bocker_help "$0" ;;
    119. esac

    项目是7年前的，很多东西都过时了，还依赖btrfs。不过我们可以从这里面简单一窥docker到底在干嘛。