Check whether live Docker container volumes exist

check-container-volumes.sh

#!/usr/bin/env bash
#
# check-container-volumes.sh
#
# Iterates over all running Docker containers and, for each mount/volume,
# reports whether the associated directory on the host exists.
#
# Notes:
#   - Must be run ON the Docker host (paths are checked on the local
#     filesystem). For named volumes the source lives under
#     /var/lib/docker/volumes/<name>/_data, which usually requires root,
#     so you may need to run this with sudo.
#   - Exits non-zero if any expected source path is missing.
#
set -uo pipefail

# Make sure docker is available.
if ! command -v docker >/dev/null 2>&1; then
    echo "Error: docker command not found." >&2
    exit 1
fi

# Field separator for parsing inspect output. We use ASCII Unit Separator
# (0x1F) instead of a tab: tab is IFS-whitespace, so `read` would collapse
# the empty .Name field of bind mounts and shift every column over by one.
sep=$'\x1f'

# Collect running container IDs (container IDs contain no whitespace,
# so word-splitting the output here is safe).
containers=$(docker ps -q)

if [ -z "$containers" ]; then
    echo "No running containers found."
    exit 0
fi

exit_code=0

for cid in $containers; do
    name=$(docker inspect --format '{{.Name}}' "$cid" | sed 's#^/##')
    echo "=== Container: $name ($cid) ==="

    # One line per mount, fields separated by 0x1F:
    # TYPE <sep> NAME <sep> SOURCE <sep> DESTINATION
    fmt="{{range .Mounts}}{{.Type}}${sep}{{.Name}}${sep}{{.Source}}${sep}{{.Destination}}{{\"\\n\"}}{{end}}"
    mounts=$(docker inspect --format "$fmt" "$cid")

    if [ -z "$mounts" ]; then
        echo "  (no volumes or bind mounts)"
        echo
        continue
    fi

    while IFS="$sep" read -r type vol_name source destination; do
        [ -z "$type" ] && continue

        # Build a readable label, e.g. "volume:mydata" or "bind".
        label="$type"
        [ -n "$vol_name" ] && label="$type:$vol_name"

        if [ -z "$source" ]; then
            # tmpfs and similar have no host source path.
            echo "  [$label] -> $destination : no host source path"
        elif [ -d "$source" ]; then
            echo "  [$label] DIR EXISTS          $source -> $destination"
        elif [ -e "$source" ]; then
            # Bind mount of a single file rather than a directory.
            echo "  [$label] EXISTS (not a dir)  $source -> $destination"
        else
            echo "  [$label] MISSING             $source -> $destination"
            exit_code=1
        fi
    done <<< "$mounts"

    echo
done

exit "$exit_code"