added userdocker attach ... sub-command, allowing to re-attach to own containers

Author: joernhees

CHANGELOG

@@ -21,6 +21,8 @@ New features:
   user_home.
 - userdocker version command will include userdocker version information.
 - Use of DOCKER_HOST env var will raise an ERROR.
+- Users can now re-attach to their previously started containers (in case of
+  connection loss for example).
 - Improved support for nvidia-docker's NV_GPU env var, which is now checked
   against admin config options:
 

README.rst

@@ -50,6 +50,9 @@ Sample Usage:
     # (docker run) run a debian image with user (read-only) mounted home
     sudo userdocker run -it --rm -v $HOME:$HOME:ro debian bash
 
+    # (docker attach) re-attach to own container after connection loss
+    sudo userdocker attach 438c7648e76b
+
     # (docker ps) list running containers
     sudo userdocker ps
 

userdocker/config/default.py

@@ -56,6 +56,7 @@
 # The following allows you to specify which docker top level commands a user can
 # run at all (still restricted by the following settings):
 ALLOWED_SUBCOMMANDS = [
+    'attach',  # allows users to re-attach to _their_ containers
     'dockviz',  # tree visualization of images
     'images',
     'load',  # see RUN_PULL as well
@@ -78,6 +79,9 @@
 # The following arguments are available to the user for the given command:
 # (aliases are supported as tuples below, but not in ARGS_ALWAYS)
 ARGS_AVAILABLE = {
+    'attach': [
+        '--no-stdin',
+    ],
     'images': [
         ('-a', '--all'),
         '--digests',
@@ -173,13 +177,6 @@
     ]
 }
 
-# By default userdocker will set USERDOCKER and USERDOCKER_USER ENV vars to the
-# container. They are used by userdocker internally and might in future be used
-# to allow users to interact with their previously started containers for
-# example. Only set to False if you know what you're doing and need a "cleaner"
-# env for some reason.
-ENV_VARS_SET_USERDOCKER_META_INFO = True
-
 
 # nvidia docker specific settings
 # The following settings allow to restrict the way users can use nvidia GPUs

userdocker/subcommands/__init__.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+from .attach import *
 from .dockviz import *
 from .images import *
 from .ps import *

userdocker/subcommands/attach.py

@@ -0,0 +1,66 @@
+# -*- coding: utf-8 -*-
+
+import json
+import logging
+
+from ..config import uid
+from ..helpers.cmd import init_cmd
+from ..helpers.exceptions import UserDockerException
+from ..helpers.execute import exec_cmd
+from ..helpers.logger import logger
+from ..helpers.parser import init_subcommand_parser
+
+
+def parser_attach(parser):
+    sub_parser = init_subcommand_parser(parser, 'attach')
+
+    sub_parser.add_argument(
+        "--detach-keys",
+        help="Override the key sequence for detaching a container",
+    )
+
+    sub_parser.add_argument(
+        "container",
+        help="container's ID or name to attach to"
+    )
+
+
+def exec_cmd_attach(args):
+    cmd = init_cmd(args)
+
+    if args.detach_keys:
+        cmd += ['--detach-keys', args.detach_keys]
+
+    container = args.container
+    container_env = exec_cmd(
+        [
+            args.executor_path, 'inspect',
+            '--format', '{{json .Config.Env}}',
+            container
+        ],
+        return_status=False,
+        loglvl=logging.DEBUG,
+    )
+    if not container_env:
+        raise UserDockerException(
+            'ERROR: could not find container %s' % container
+        )
+    userdocker_uid_env = [
+        env for env in json.loads(container_env)
+        if env.startswith('USERDOCKER_UID')
+    ]
+    if not userdocker_uid_env:
+        raise UserDockerException(
+            'ERROR: could not find USERDOCKER_UID env var in container %s'
+            % container
+        )
+    userdocker_uid = int(userdocker_uid_env[0].split('USERDOCKER_UID=')[1])
+    logger.debug(
+        "Container %s was started by user id %d", container, userdocker_uid)
+    if uid != userdocker_uid:
+        raise UserDockerException(
+            'ERROR: container %s was started by %d, but you are %d. Permission '
+            'denied!' % (container, userdocker_uid, uid)
+        )
+
+    exec_cmd(cmd, dry_run=args.dry_run)

userdocker/subcommands/run.py

@@ -12,7 +12,6 @@
 from ..config import CAPS_DROP
 from ..config import ENV_VARS
 from ..config import ENV_VARS_EXT
-from ..config import ENV_VARS_SET_USERDOCKER_META_INFO
 from ..config import NV_ALLOWED_GPUS
 from ..config import NV_DEFAULT_GPU_COUNT_RESERVATION
 from ..config import NV_MAX_GPU_COUNT_RESERVATION
@@ -214,12 +213,11 @@ def exec_cmd_run(args):
         prepare_nvidia_docker_run(args)
 
     env_vars = ENV_VARS + ENV_VARS_EXT.get(args.executor, [])
-    if ENV_VARS_SET_USERDOCKER_META_INFO:
-        env_vars += [
-            "USERDOCKER=%s" % __version__,
-            "USERDOCKER_USER=%s" % user_name,
-            "USERDOCKER_UID=%d" % uid,
-        ]
+    env_vars += [
+        "USERDOCKER=%s" % __version__,
+        "USERDOCKER_USER=%s" % user_name,
+        "USERDOCKER_UID=%d" % uid,
+    ]
     for env_var in env_vars:
         cmd += ['-e', env_var]