Dir Safe Mirror (Bash)

A small interactive Bash script to mirror one directory into another (destructive sync) or perform a non‑destructive copy using your choice of engine:

• Standard: rm -rf + cp -a (mirror) or cp -au (copy mode)
• rsync: rsync -aH --delete --info=progress2 (mirror) or rsync -aH --info=progress2 (copy mode)
• rclone: rclone sync (mirror) or rclone copy (copy mode)

It performs safety checks and can make a backup of the destination in /tmp before syncing.

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Features

• Engine selection: cp, rsync, or rclone

• Preview before copying: total files, total size, optional per‑file list

• Two modes:

  • Mirror (default): destination becomes an exact mirror of source (extra files at destination are removed)
  • Copy mode (--copy): non‑destructive; extra files at destination are kept

• Safety checks:

  • Source and destination must differ
  • Destination / is refused
  • Extra confirmation for “sensitive” paths (/etc, /var, /usr, …)
  • Detects nesting (src inside dst or dst inside src)

• Destination backup to /tmp using a timestamped temp directory (can be skipped)

• Graceful abort on Ctrl+C

• Least privilege: elevates only when required (mkdir/rm, optional installs); can be forced off with --no-sudo

• Config file with sane defaults, auto‑created on first run

• Logging to a file (configurable; defaults under XDG state directory)

• Skippable steps via --skip or config: preview, backup, safety

• Non‑interactive paths via -s/--src and -d/--dst; default tool via -t/--tool

• Dry run mode via --dry-run or config

• Unattended runs with --no-confirm (auto‑answers prompts with their default)

If rsync/rclone are missing, the script can offer to install them (with your confirmation). Otherwise, pick another engine.

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Requirements

• Linux with Bash ≥ 4.2 (uses ${var,,} and declare -g)

• GNU coreutils (for readlink -f)

• GNU find (uses -printf in preview)

• Optional:

  • rsync for the rsync engine
  • rclone for the rclone engine

macOS is not targeted (no readlink -f by default, older Bash).

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Install

Save the script as dsm, then make it executable:

chmod +x dsm

Optionally place it somewhere on your PATH.

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Configuration

Location (auto‑created if missing):

• Primary: ${XDG_CONFIG_HOME:-$HOME/.config}/dsm/config
• Legacy (read if present; not auto‑created): ~/.dsm/config

Format: key=value. Lines starting with # are comments. The file is created with chmod 600.

Precedence: CLI > config > built‑in defaults. For skip lists, values are merged (union).

Defaults written on first run:

# dsm configuration (auto-created)
# Keys: tool, log, skip, dry_run, no_sudo, src, dst, rsync_opts, rclone_opts, cp_opts

tool=cp
log=${XDG_STATE_HOME:-$HOME/.local/state}/dsm/dsm.log
skip=
dry_run=false
no_sudo=false
src=
dst=
rsync_opts=
rclone_opts=
cp_opts=

Supported keys:

• tool=cp|rsync|rclone — default engine.
• log=/path/to/file — append logs here (directory auto‑created). Default lives under ${XDG_STATE_HOME:-$HOME/.local/state}/dsm/dsm.log.
• skip=preview,backup,safety — comma‑separated steps to skip.
• dry_run=true|false — run without changing anything.
• no_sudo=true|false — disallow privilege escalation; operations requiring it will fail.
• src=/path / dst=/path — default source/destination (non‑interactive).
• rsync_opts=... / rclone_opts=... / cp_opts=... — extra flags appended to the engine command.

There is no config key for copy vs mirror. Use --copy to enable copy mode for a run.

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CLI overview

• -s, --src DIR — set source directory (non‑interactive)
• -d, --dst DIR — set destination directory (non‑interactive)
• -t, --tool cp|rsync|rclone — choose engine
• --dry-run — simulate actions; no changes
• --skip preview,backup,safety — skip steps (values merged with config)
• --no-sudo — never escalate privileges (sudo/doas disabled)
• --no-backup — skip destination backup (same as --skip backup)
• --no-confirm — answer prompts automatically with their default (safety prompts default to No)
• --copy — non‑destructive copy mode (keeps extra files in destination)
• --config FILE — use explicit config path (auto‑created if missing)
• --log FILE — override log file path

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Usage

Interactive

./dsm

You will be prompted to:

1. Enter the source directory.

2. Enter (or create) the destination directory.

3. Confirm if the destination looks “sensitive”.

4. Pick the engine:

   1) Standard (cp + rm)
   2) rsync
   3) rclone
   

On completion, the script prints where the destination backup was saved.

Abort at any time with Ctrl+C. In yes/no prompts, q, quit, or exit will also exit.

Non‑interactive examples

Select source/destination and engine:

./dsm -s ./src -d ./dst -t rsync

Dry‑run with preview auto‑enabled, no changes applied:

./dsm --dry-run -s ./src -d ./dst -t cp

Skip preview and backup (safety still on):

./dsm -s ./src -d ./dst --skip preview,backup -t rclone

Force no privilege escalation and no interactive questions:

./dsm -s ./src -d ./dst -t rsync --no-sudo --no-confirm

Enable copy mode (keep extra files at destination):

# cp engine: non-destructive update-in-place
./dsm -s ./src -d ./dst -t cp --copy

# rsync engine: no --delete
./dsm -s ./src -d ./dst -t rsync --copy

# rclone engine: use 'rclone copy'
./dsm -s ./src -d ./dst -t rclone --copy

Use a custom config file:

./dsm --config /path/to/custom.cfg -s ./src -d ./dst

Send logs to a specific file (overrides config):

./dsm --log /var/log/dsm/run.log -s ./src -d ./dst

Note: CLI flags override the config file. skip values from CLI and config are merged.

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Preview logic

• cp (mirror, default): destination is cleared before copy → preview = all source files.
• cp (copy mode, --copy): non‑destructive → preview = delta (files where size OR mtime differs).
• rsync / rclone: preview = delta (size OR mtime differs) regardless of mode.

The preview shows:

• Count and total size in source
• Count and total size that will be transferred
• Optional per‑file list

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Engine behavior

Engine	Mirror command (simplified)	Copy‑mode command (simplified)	Notes
cp	rm -rf "$dst"/{*,.[!.]*,..?*} → cp -a "$src"/. "$dst"/	cp -au "$src"/. "$dst"/	Mirror clears destination (incl. dotfiles); copy mode updates in place and keeps extras.
rsync	rsync -aH --delete --info=progress2 $rsync_opts "$src"/ "$dst"/	rsync -aH --info=progress2 $rsync_opts "$src"/ "$dst"/	Copy mode omits --delete, so extra files at destination are preserved.
rclone	rclone sync --progress --copy-links --local-no-check-updated $rclone_opts "$src" "$dst"	rclone copy --progress --copy-links --local-no-check-updated $rclone_opts "$src" "$dst"	Copy mode uses copy instead of sync.

Extra per‑engine options from the config are appended when present.

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Backup

Before syncing, the current destination is copied to a unique, timestamped temp directory, e.g.:

/tmp/<basename(dst)>.YYYYMMDDTHHMMSSmmm.XXXX

Example:

/tmp/data.20250822T203012123.Kf8s

Backups remain in /tmp until the system cleans them up. You can skip this step with --no-backup, --skip backup, or skip=backup in the config.

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Logging

If log is set (default: ${XDG_STATE_HOME:-$HOME/.local/state}/dsm/dsm.log), the script appends structured lines with timestamps (UTC), selected tool, paths, preview summary, and final status. The log directory is created automatically.

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Exit codes

• 0 — success (or a deliberate exit via prompt)
• 1 — validation/operation error
• 130 — aborted by user (Ctrl+C)

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Example session

Enter source directory: /data/src
Enter destination directory: /data/dst
Destination is a sensitive directory: /data/dst
Do you want to continue? (y/N): y
Are you absolutely sure? (y/N): y

Choose copy tool:
1) Standard (cp + rm)
2) rsync
3) rclone
Select: 2
Selected: rsync

Preview — delta (size+mtime)
Source files:   21
Source size:    543 KB (556556 bytes)
Will transfer:  5
Transfer size:  123 KB (126000 bytes)

The task was completed successfully. Previous data backed up to: /tmp/dst.20250822T203012123.w3Qf

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Known limitations

• Linux‑only assumptions (readlink -f, Bash ≥ 4.2; GNU find -printf).
• No checksum comparison in preview (size+mtime only).
• Optional package installation is offered only when a supported package manager is detected.
• Legacy config path ~/.dsm/config is read if present but is not auto‑created.