External Disk Permissions and Disk Usage

First PublishedMay 5, 2026ByAtif Alam

A practical runbook for ownership and access problems on macOS external volumes and for interactive disk usage with dua and related CLI tools (Homebrew, Apple Silicon). Replace /Volumes/YourDrive and example UIDs (44222) with your volume path and orphaned IDs.

Install Tools

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# Interactive disk usage analyzer
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brew install dua-cli
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# eza (icons + tree listing)
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brew install eza
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# Alternative TUI disk analyzer
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brew install ncdu

Diagnose the Drive

Before changing ownership, inspect the current state:

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# List top-level files and owners
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sudo /bin/ls -lhA /Volumes/YourDrive
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# Filesystem type and ownership status
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diskutil info /Volumes/YourDrive | grep -E "Type|File System|Owners"
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# How the volume is mounted
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mount | grep YourDrive
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# Orphaned UIDs often show as numbers, not names
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sudo /bin/ls -lhA /Volumes/YourDrive | awk '{print $3}' | sort | uniq -c | sort -rn

Common owner states:

Owner shown	Meaning
`yourname`	Owned by your current login
`root`	System metadata — usually leave as-is
`44222`	Example orphaned UID — from a deleted or migrated account
`_unknown`	macOS cannot resolve the UID
Previous Mac username	Migration or copy from another machine

Fix TCC / Full Disk Access

If tools report Operation not permitted (os error 1) even when using sudo, macOS is enforcing TCC, not Unix permissions. sudo does not bypass TCC.

Grant Full Disk Access to your terminal app when bulk reads (find, indexing tools) hit protected locations — otherwise commands fail regardless of UID 0.

Steps:

Open System Settings → Privacy & Security → Full Disk Access
Use + and add your terminal (iTerm2, Terminal.app, Warp, and so on)
Add /usr/bin/sudo if your workflow relies on escalation helpers TCC associates with it
Turn the entries On
Quit fully and reopen the terminal session

Test:

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/bin/ls /Volumes/YourDrive

Disable Volume Ownership

External volumes often enforce POSIX ownership. That can block access until metadata is repaired or ownership behavior is relaxed for that volume:

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diskutil info /Volumes/YourDrive | grep "Owners"
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sudo diskutil disableOwnership /Volumes/YourDrive
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diskutil info /Volumes/YourDrive | grep "Owners"
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# Owners: Disabled

Disabling ownership is a normal choice for removable or backup disks you administer yourself.

Do not run disableOwnership on your Macintosh HD / system volume. Use this only on external volumes you intend to manage as bulk data stores.

Fix Orphaned File Ownership

Identify Orphaned Files

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# Files owned by a known old UID (example: 44222)
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sudo find /Volumes/YourDrive -user 44222 2>/dev/null | wc -l
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# Paths with no valid user mapping
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sudo find /Volumes/YourDrive -nouser 2>/dev/null | wc -l

Fix Ownership — Targeted Approach (Fastest)

Prefer this when ls -lhA shows a small set of top-level folders carrying bad ownership:

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#!/usr/bin/env bash
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set -euo pipefail
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VOLUME="/Volumes/YourDrive"
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ME="$(whoami)"
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DIRS=(
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  "data-from-old-mac"
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  "Dropbox_archive"
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  "Documents"
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  "Projects"
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)
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echo "Fixing ownership as: $ME"
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for dir in "${DIRS[@]}"; do
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  full_path="$VOLUME/$dir"
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  if [ -d "$full_path" ]; then
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    echo "Processing: $dir"
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    sudo chown -R "$ME" "$full_path" 2>/dev/null &
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  else
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    echo "Skipping (not found): $dir"
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  fi
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done
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wait
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echo "Done!"

Save and run:

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chmod +x ~/fix_ownership.sh
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~/fix_ownership.sh

Fix Ownership — Bulk Approach (Slower but Thorough)

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sudo find /Volumes/YourDrive -user 44222 -print0 | \
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  xargs -0 -P 8 -n 500 sudo chown "$(whoami)" 2>/dev/null
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sudo find /Volumes/YourDrive -nouser -print0 | \
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  xargs -0 -P 8 -n 500 sudo chown "$(whoami)" 2>/dev/null

Parallelism raises I/O load; reduce -P on slow disks.

Fix Specific Paths

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sudo chown "$(whoami)" /Volumes/YourDrive/SomeFile.zip
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sudo chown -R "$(whoami)" "/Volumes/YourDrive/Some Folder"
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sudo chown "$(whoami)" \
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  "/Volumes/YourDrive/file1.zip" \
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  "/Volumes/YourDrive/Folder Name" \
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  "/Volumes/YourDrive/another-file"

Unlock macOS-Locked Files (If chown Still Fails)

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sudo chflags -R nouchg /Volumes/YourDrive 2>/dev/null
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sudo chown -R "$(whoami)" /Volumes/YourDrive 2>/dev/null

Verify Ownership Is Clean

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sudo find /Volumes/YourDrive -user 44222 2>/dev/null | wc -l
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sudo find /Volumes/YourDrive -nouser 2>/dev/null | wc -l
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/bin/ls -lhA /Volumes/YourDrive | awk '{print $3, $4, $NF}' | column -t
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/bin/ls -lhA /Volumes/YourDrive/SomeFolder | grep "44222\|_unknown"

Expected clean state:

Path type	Expected owner
Your data dirs/files	Your login
`.Spotlight-V100`	`root`
`.fseventsd`	`root`
`.Trashes`	`root`
`.DocumentRevisions*`	Often `root`
`Backups.backupdb`	`root` (Time Machine layout)

View Folder Sizes with `dua`

A fuller dua walkthrough (install, aggregate mode, troubleshooting) lives in dua (disk usage). The following stays oriented to external volumes once access works.

Basic Usage

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dua i /Volumes/YourDrive
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dua i ~

Keyboard Shortcuts inside `dua`

Key	Action
`↑` / `↓`	Move selection
`Enter`	Open directory
`d`	Mark for deletion
`u`	Undo mark
`q`	Quit
`?`	Help

Skip System Metadata Directories

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dua i /Volumes/YourDrive \
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  --ignore-dirs /Volumes/YourDrive/.DocumentRevisions-V100 \
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  --ignore-dirs /Volumes/YourDrive/.Spotlight-V100 \
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  --ignore-dirs /Volumes/YourDrive/.fseventsd

Adjust paths if your volume uses slightly different Spotlight or revisions folder names.

Non-Interactive Output

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dua /Volumes/YourDrive

Bonus: `eza` Tree View

eza lists trees with flair; combine with dua when you care about recursive directory totals:

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eza --tree --long -h --level=2 /Volumes/YourDrive
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eza --tree --long -h --level=2 --icons /Volumes/YourDrive

Recommended Aliases for `~/.zshrc`

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alias ls='eza --icons --group-directories-first'
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alias ll='eza -lhA --icons --group-directories-first'
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alias lt='eza --tree --icons --level=2'
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alias lta='eza --tree --icons --long -h --level=3'

Individual file sizes in eza are not rolled-up folder sizes — use dua when choosing what to delete or archive.

Quick Folder Summary without `dua`

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du -sh /Volumes/YourDrive/* 2>/dev/null | sort -rh

Troubleshooting

`Operation not permitted (os error 1)` Even With `sudo`

TCC restriction. Configure Full Disk Access as in Fix TCC / Full Disk Access above.

`chown: /Volumes/YourDrive: Operation not permitted` at the Volume Root

Harmless: macOS guards the synthetic mount-point; chown targets inside the volume still work.

`find` Is Too Slow on a Large Drive

Use Fix Ownership — Targeted Approach (Fastest) for known folder names instead of scanning the entire tree repeatedly.

`colorls` or Ruby Gems Break Your Shell Prompt

Prefer eza (Homebrew-maintained C/Rust toolchain, no Rubygems requirement):

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brew install eza

`dua` Errors on `.Spotlight` or `.DocumentRevisions`

Add matching --ignore-dirs paths; those trees are indexed or versioned outside normal cleanup workflows.

`_unknown` Still Appears After `chown`

If ownership semantics are relaxed but Finder or ls still looks odd, re-run a -nouser sweep:

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sudo find /Volumes/YourDrive -nouser -print0 | xargs -0 -P 4 sudo chown "$(whoami)" 2>/dev/null

Generated for macOS with Homebrew; workflows were validated on Apple Silicon Macs running recent macOS versions.