Add '--instance' option to 'netlab down' command

This change allows you to use 'netlab down' to shut down an instance
running in another directory. It's useful primarily when you want to
start a lab but 'netlab up' complains that the 'default' instance is
already running.

docs/netlab/down.md

@@ -3,12 +3,12 @@
 
 **netlab down** destroys a virtual lab created with **[netlab up](up.md)** command.
 
-This command uses the lab topology or the snapshot file created by **netlab up** or **[netlab create](create.md)** to find the virtualization provider, and executes provider-specific CLI commands to destroy the virtual lab.
+This command uses the lab topology or the snapshot file created by **netlab up** or **[netlab create](create.md)** to find the virtualization provider and executes provider-specific CLI commands to destroy the virtual lab.
 
 ## Usage
 
 ```
-usage: netlab down [-h] [-v] [--cleanup] [--dry-run] [--force] [--snapshot [SNAPSHOT]]
+usage: netlab down [-h] [-v] [--cleanup] [--dry-run] [-i INSTANCE] [--force] [--snapshot [SNAPSHOT]]
 
 Destroy the virtual lab
 
@@ -17,18 +17,21 @@ options:
   -v, --verbose         Verbose logging (where applicable)
   --cleanup             Remove all configuration files created by netlab create
   --dry-run             Print the commands that would be executed, but do not execute them
+  -i INSTANCE, --instance INSTANCE
+                        Specify lab instance to shut down
   --force               Force shutdown or cleanup (use at your own risk)
 ```
 
 Notes:
 
 * **netlab down** needs transformed topology data to find the virtualization provider and link (bridge) names.
 * **netlab down** reads the transformed topology from `netlab.snapshot.yml` file created by **netlab up** or **netlab create**. You can specify a different snapshot file name, but you really should not.
+* With the `--instance` flag, you can shut down a lab instance running in a different directory. Use the `netlab status --all` command to display all running instances.
 * Use the `--cleanup` flag to delete all Ansible-, Vagrant- or containerlab-related configuration files.
 * Use the `--force` flag with the `--cleanup` flag if you want to clean up the directory even when the virtualization provider fails during the shutdown process.
 
 ## Conflict Resolution
 
 **netlab down** command checks the _netlab_ status file (default: `~/.netlab/status.yml`) to verify that the current lab instance (default: `default`) is not running in another directory. You can decide to proceed if you want to remove _netlab_ artifacts from the current directory, but the shutdown/cleanup process might impact the lab instance running in another directory.
 
-After a successful completion, **netlab down** command removes the `netlab.lock` file from the current directory, and all information about the lab instance from the _netlab_ status file.
+After a successful completion, the **netlab down** command removes the `netlab.lock` file from the current directory and all information about the lab instance from the _netlab_ status file.

netsim/cli/down.py

@@ -15,7 +15,7 @@
 from . import external_commands, set_dry_run, is_dry_run
 from . import lab_status_change,fs_cleanup,load_snapshot,parser_add_snapshot
 from .. import providers
-from ..utils import status,strings,log
+from ..utils import status,strings,log,read as _read
 from .up import provider_probes
 #
 # CLI parser for 'netlab down' command
@@ -41,6 +41,11 @@ def down_parse(args: typing.List[str]) -> argparse.Namespace:
     dest='dry_run',
     action='store_true',
     help='Print the commands that would be executed, but do not execute them')
+  parser.add_argument(
+    '-i','--instance',
+    dest='instance',
+    action='store',
+    help='Specify lab instance to shut down')
   parser.add_argument(
     '--force',
     dest='force',
@@ -166,11 +171,33 @@ def stop_all(topology: Box, args: argparse.Namespace) -> None:
     if not args.force:
       sys.exit(1)
 
+"""
+Find a lab instance and change directory so the rest of the shutdown
+process works from that directory
+"""
+def change_lab_instance(instance: str) -> None:
+  topology = _read.system_defaults()
+  lab_states = status.read_status(topology)
+  if not instance in lab_states:
+    log.fatal(f'Unknown instance {instance}, use "netlab status --all" to display running instances')
+
+  target_dir = lab_states[instance].dir
+  try:
+    os.chdir(target_dir)
+  except Exception as ex:
+    log.fatal(f'Cannot change directory to {target_dir}: {str(ex)}')
+
+  log.status_green('CHANGED','')
+  print(f'Current directory changed to {target_dir}, continuing the shutdown process')
+
 def run(cli_args: typing.List[str]) -> None:
   args = down_parse(cli_args)
   set_dry_run(args)
+  if args.instance:
+    change_lab_instance(args.instance)
 
   topology = load_snapshot(args)
+  log.status_success()
   print(f"Read transformed lab topology from snapshot file {args.snapshot}")
 
   mismatch = lab_dir_mismatch(topology,args)

netsim/utils/log.py

@@ -303,11 +303,15 @@ def repeat_warnings(cmd: str) -> None:
 """
 Print colored status headers
 """
+def status_green(stat: str, txt: str) -> None:
+  stat = f'[{stat}]'
+  strings.print_colored_text(f'{stat:10s}','green',txt)
+
 def status_created() -> None:
-  strings.print_colored_text('[CREATED] ','green','Created ')
+  status_green('CREATED','Created')
 
 def status_success() -> None:
-  strings.print_colored_text('[SUCCESS] ','green','OK: ')
+  status_green('SUCCESS','OK: ')
 
 def section_header(label: str, text: str, color: str = 'green') -> None:
   if not strings.rich_color: