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core: robust Docker diagnostics using direct system checks (Fixes #34) #343

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Merged
tfoote merged 2 commits into from
Jan 27, 2026
Merged

core: robust Docker diagnostics using direct system checks (Fixes #34) #343

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4b15a39
Improve Docker availability and permission detection (Fixes #34)
T-Rajeev30 Jan 24, 2026
d947562
Address maintainer feedback: move diagnostics to exception handler
T-Rajeev30 Jan 27, 2026
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2 changes: 1 addition & 1 deletion src/rocker/cli.py
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@ def main():
extension_manager.extend_cli_parser(parser, default_args)
except DependencyMissing as ex:
# Catch errors if docker is missing or inaccessible.
parser.error("DependencyMissing encountered: %s" % ex)
parser.error(str(ex))

args = parser.parse_args()
args_dict = vars(args)
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45 changes: 39 additions & 6 deletions src/rocker/core.py
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Expand Up @@ -221,12 +221,45 @@ def get_docker_client():
docker_client.ping()
return docker_client
except (docker.errors.DockerException, docker.errors.APIError, ConnectionError) as ex:
raise DependencyMissing('Docker Client failed to connect to docker daemon.'
' Please verify that docker is installed and running.'
' As well as that you have permission to access the docker daemon.'
' This is usually by being a member of the docker group.'
' The underlying error was:\n"""\n%s\n"""\n' % ex)

# Connection failed - run diagnostics to provide helpful error

# Check 1: Is Docker installed?
import shutil
if not shutil.which("docker"):
raise DependencyMissing(
"Docker is not installed.\n"
"Install instructions:\n"
" https://docs.docker.com/engine/install/"
)

# Check 2: Does Docker socket exist?
socket_path = "/var/run/docker.sock"
if not os.path.exists(socket_path):
raise DependencyMissing(
"Docker daemon is not running.\n\n"
"Fix:\n"
" sudo systemctl start docker"
)

# Check 3: Can user access the socket?
if not os.access(socket_path, os.R_OK | os.W_OK):
user = os.getenv("USER", "your-user")
raise DependencyMissing(
"Docker permission error.\n"
f"User '{user}' does not have access to the Docker socket.\n\n"
"Fix:\n"
f" sudo usermod -aG docker {user}\n"
" log out and log back in"
)

# All checks passed but connection still failed
raise DependencyMissing(
"Docker daemon is not responding.\n\n"
"Verify:\n"
" - Docker is running\n"
" - `docker ps` works\n\n"
f"Original error: {ex}"
)
def get_user_name():
userinfo = pwd.getpwuid(os.getuid())
return getattr(userinfo, 'pw_' + 'name')
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