My nix-darwin and NixOS config
macmini: simplify Time Machine to local disk only, add setup doc
- Drop SMB server fallback from the activation script; local APFS
volume is the only supported destination
- Script skips gracefully if the disk isn't plugged in at rebuild time
- Add docs/time-machine.md covering one-time volume creation steps
- Clean up inline comments in macmini/default.nix and options.nix
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docs/time-machine.md
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docs/time-machine.md
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# Time Machine Setup
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Backups go to a dedicated APFS volume on the external CT2000X9SSD9 (USB, `disk4`/`disk5`).
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The `nrs` activation script handles registration and mounting automatically on every rebuild —
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this doc covers the one-time volume creation only.
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## First-time setup
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### 1. Create the Time Machine APFS volume
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```bash
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sudo diskutil apfs addVolume disk5 APFS "Time Machine"
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```
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> `disk5` is the APFS container that lives on `disk4s2`. Run `diskutil list` to confirm
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> it's still the right identifier before running this.
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### 2. Get the volume UUID
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```bash
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diskutil info "/Volumes/Time Machine" | grep "Volume UUID"
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```
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### 3. Set the UUID in the config
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In `hosts/macmini/default.nix`:
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```nix
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myConfig.darwin.externalDisk.timeMachineVolumeUUID = "<uuid from step 2>";
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```
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### 4. Rebuild
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```bash
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nrs
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```
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The activation script will mount the volume if needed and register it as a Time Machine
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destination. Backups run on a weekly interval (configured via `tmutil setbackupinterval`).
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## How it works
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`modules/darwin/system.nix` runs a `system.activationScripts.timeMachineDestination` on
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every `nrs`. It:
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1. Looks up the volume by UUID via `diskutil info`
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2. Mounts it if it exists but isn't mounted
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3. Registers it with `tmutil setdestination -a` if not already registered
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4. Skips silently if the disk isn't plugged in
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Setting `myConfig.darwin.externalDisk.timeMachineVolumeUUID = null` disables the script
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entirely.
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## Server Time Machine (not configured)
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A Samba/netatalk-based network Time Machine destination on the server is not currently set up.
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If desired in future, the relevant option is `myConfig.server.timemachine` — see
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`modules/options.nix` for the available sub-options.
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hosts/macmini/default.nix
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hosts/macmini/default.nix
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system.defaults.smb.NetBIOSName = "macmini";
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# ── External disk (CT2000X9SSD9, APFS container on disk4s2) ───────────────
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# After setting up APFS volumes on the external disk (see README), set:
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#
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# Time Machine (local, priority 1 — fills in after one-time volume creation):
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# myConfig.darwin.externalDisk.timeMachineVolumeUUID = "<uuid from diskutil>";
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#
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# Server Time Machine (fallback, priority 2 — enable once server has netatalk):
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# myConfig.server.timemachine.enable = true;
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#
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# Leave both at their defaults (null / false) to skip Time Machine entirely.
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# See docs/time-machine.md for first-time setup instructions.
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myConfig.darwin.externalDisk.timeMachineVolumeUUID = "9217DB34-722B-4596-8ADD-20C8060FC257";
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# Timezone — driven from myConfig.timeZone
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modules/darwin/system.nix
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modules/darwin/system.nix
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# ── Time Machine destination ──────────────────────────────────────────────
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# No native nix-darwin option exists for tmutil setdestination, so we use an
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# activation script. Priority order:
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# 1. Local APFS volume on external disk (myConfig.darwin.externalDisk.timeMachineVolumeUUID)
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# 2. SMB server share (myConfig.server.timemachine.enable = true)
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# 3. Skip — no Time Machine configured
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# activation script. Skipped entirely if timeMachineVolumeUUID is null.
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#
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# Server first-time setup (one-off, interactive — stores password in macOS keychain):
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# sudo tmutil setdestination -p smb://<user>@server/TimeMachine
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# After that, nrs registers it automatically on every rebuild without prompting.
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# The volume is auto-mounted if it exists but isn't mounted yet.
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# Idempotent: skipped if the destination is already registered.
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system.activationScripts.timeMachineDestination = lib.mkIf
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(cfg.darwin.externalDisk.timeMachineVolumeUUID != null || cfg.server.timemachine.enable)
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(cfg.darwin.externalDisk.timeMachineVolumeUUID != null)
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{
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text =
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let
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localUUID = cfg.darwin.externalDisk.timeMachineVolumeUUID;
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hasLocal = localUUID != null;
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serverUrl = "smb://${cfg.user.username}@server/${cfg.server.timemachine.shareName}";
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hasServer = cfg.server.timemachine.enable;
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uuid = cfg.darwin.externalDisk.timeMachineVolumeUUID;
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in
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''
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_register_tm() {
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local dest="$1"
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if /usr/bin/tmutil destinationinfo 2>/dev/null | /usr/bin/grep -qF "$dest"; then
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echo " Time Machine: $dest already registered, skipping"
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else
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echo " Time Machine: registering $dest"
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# -a adds alongside existing destinations rather than replacing.
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# For SMB, credentials must already be in the macOS keychain.
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/usr/bin/tmutil setdestination -a "$dest" 2>&1 || \
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echo " WARNING: could not register $dest"
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fi
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}
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echo "Checking local Time Machine volume (UUID=${uuid})..."
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_info=$(/usr/sbin/diskutil info "${uuid}" 2>/dev/null)
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if [ $? -ne 0 ]; then
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echo " Disk not found — skipping Time Machine setup."
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exit 0
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fi
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${lib.optionalString hasLocal ''
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# ── Priority 1: local APFS volume ──────────────────────────────────
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echo "Checking local Time Machine volume (UUID=${localUUID})..."
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_info=$(/usr/sbin/diskutil info "${localUUID}" 2>/dev/null)
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if [ $? -eq 0 ]; then
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_mount=$(echo "$_info" | /usr/bin/awk '/Mount Point/ { for(i=3;i<=NF;i++) printf "%s ", $i; print "" }' | /usr/bin/sed 's/ *$//')
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if [ -z "$_mount" ] || [ "$_mount" = "Not applicable (no file system)" ]; then
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echo " Volume exists but not mounted — mounting..."
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/usr/sbin/diskutil mount "${localUUID}" 2>&1
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_mount=$(/usr/sbin/diskutil info "${localUUID}" 2>/dev/null | /usr/bin/awk '/Mount Point/ { for(i=3;i<=NF;i++) printf "%s ", $i; print "" }' | /usr/bin/sed 's/ *$//')
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fi
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if [ -n "$_mount" ] && [ "$_mount" != "Not applicable (no file system)" ]; then
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_register_tm "$_mount"
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# Local disk found and registered — skip server check.
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return 0 2>/dev/null || exit 0
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else
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echo " Could not mount local TM volume; falling back to server."
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fi
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else
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echo " Local disk not found (UUID=${localUUID}); falling back to server."
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fi
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''}
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_mount=$(echo "$_info" | /usr/bin/awk '/Mount Point/ { for(i=3;i<=NF;i++) printf "%s ", $i; print "" }' | /usr/bin/sed 's/ *$//')
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if [ -z "$_mount" ] || [ "$_mount" = "Not applicable (no file system)" ]; then
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echo " Volume not mounted — mounting..."
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/usr/sbin/diskutil mount "${uuid}" 2>&1
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_mount=$(/usr/sbin/diskutil info "${uuid}" 2>/dev/null | /usr/bin/awk '/Mount Point/ { for(i=3;i<=NF;i++) printf "%s ", $i; print "" }' | /usr/bin/sed 's/ *$//')
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fi
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# ── Backup schedule: weekly (604800 seconds) ───────────────────────────
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/usr/bin/tmutil setbackupinterval 604800
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if [ -z "$_mount" ] || [ "$_mount" = "Not applicable (no file system)" ]; then
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echo " Could not mount volume — skipping Time Machine setup."
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exit 0
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fi
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${lib.optionalString hasServer ''
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# ── Priority 2: SMB server share ───────────────────────────────────
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echo "Checking server Time Machine share (${serverUrl})..."
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if /sbin/ping -c1 -W1 server &>/dev/null; then
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_register_tm "${serverUrl}"
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else
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echo " Server unreachable — skipping Time Machine setup."
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fi
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''}
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if /usr/bin/tmutil destinationinfo 2>/dev/null | /usr/bin/grep -qF "$_mount"; then
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echo " Already registered as Time Machine destination, skipping."
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else
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echo " Registering $_mount as Time Machine destination..."
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/usr/bin/tmutil setdestination -a "$_mount" 2>&1 || \
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echo " WARNING: tmutil setdestination failed."
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fi
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# Weekly backup interval (604800 seconds = 7 days)
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/usr/bin/tmutil setbackupinterval 604800
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'';
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};
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}
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modules/options.nix
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modules/options.nix
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darwin = {
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# ── External storage ──────────────────────────────────────────────────────
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externalDisk = {
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timeMachineVolumeUUID = mkOption {
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type = nullStr;
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default = null;
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description = ''Volume UUID of the APFS volume to use for local Time Machine backups.
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Obtain after running:
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sudo diskutil apfs addVolume disk5 APFS "Time Machine"
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diskutil info "/Volumes/Time Machine" | grep "Volume UUID"
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'';
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};
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externalDisk.timeMachineVolumeUUID = mkOption {
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type = nullStr;
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default = null;
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description = ''
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Volume UUID of the APFS volume to use for local Time Machine backups.
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Set to null to disable. See docs/time-machine.md for setup instructions.
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'';
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};
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keyboard = {