Time Machine to a Synology - Mac Backups to Your NAS

Why Back a Mac Up to the NAS

A backup is simply a second copy of your files, kept somewhere safe, so that losing the first copy is only an inconvenience and not a heartbreak. The question is where that second copy should live.

In short, the NAS turns backup from a chore you have to remember into something that just happens quietly in the background.

• It is automatic. Once set up, the Mac backs up on its own over Wi-Fi. There is no drive to plug in and no button to press.
• It is roomy. A NAS holds far more than a typical laptop, so it keeps many weeks of history, not just today's copy.
• Nothing clutters the desk. No little hard drive sitting out, no cable to trip over, no drive to forget on a trip.
• It serves the whole house. One NAS can back up several Macs at the same time.

What Time Machine Is, in Plain Words

Time Machine is Apple's built-in backup feature, included free on every Mac. Its job is to keep copies of your files as they were at different points in time - hence the name.

Imagine a shelf of photo albums, one for each hour, day, and week. Time Machine keeps a snapshot of your Mac at each of those moments. If you delete a file today, you can reach back to yesterday's snapshot and pull it out, exactly as it was.

• It runs quietly in the background - you do not have to start it.
• It keeps hourly, daily, and weekly copies, so you can go back in time.
• As the backup drive fills up, it thins out the oldest copies for you.
• You can restore a single file, or your entire Mac, from those copies.

What You Set Up on the Synology Side

Before the Mac can back up to the NAS, the NAS needs four small things in place. None of them are hard, and you only do this once.

You do all of this in DSM, which is the web screen you see when you log in to your Synology from a browser. The next few pages walk through each piece.

• A shared folder - a place on the NAS set aside just for backups.
• A user account - a login the Mac uses to reach that folder.
• SMB turned on - SMB is the language Macs and the NAS use to share files. It lives in Control Panel, under File Services.
• Time Machine enabled - a switch that tells the NAS it is allowed to receive Mac backups into that folder.

Making a Dedicated User and Folder

Think of this as giving the Mac its own labeled drawer on the NAS, and its own key to that drawer. Doing it this way keeps your backups tidy and separate from everything else.

• In DSM, open Control Panel, then Shared Folder.
• Click Create and name it something clear, like "TimeMachine."
• Choose which drive volume it lives on if you are asked.
• Finish the wizard - you now have an empty folder waiting for backups.

Set a Size Limit So It Behaves

Time Machine is greedy by nature - if you let it, it will keep making copies until it fills every bit of free space on the drive. A quota is simply a ceiling you set so it stops at a sensible point.

Your NAS probably does more than back up the Mac. It may hold photos, documents, or files for the whole family. A quota reserves a slice for backups and leaves the rest for everything else, so the two never fight over space.

• Give Time Machine roughly two to three times the size of the Mac's drive.
• A Mac with a 500 GB drive is comfortable with about 1 to 1.5 TB of quota.
• More room means more history you can reach back into.

On the Mac: Choosing the Backup Disk

With the NAS side ready, the Mac part is short. You are simply telling Time Machine, "back up to that folder on the NAS, using this login."

That is the whole hook-up. Once the Mac accepts the folder, it will begin its first backup shortly, usually on its own within a few minutes.

• On the Mac, open System Settings from the Apple menu.
• Click General, then click Time Machine.
• Click Add Backup Disk (older Macs say Select Disk).
• In the list, find your Synology and the TimeMachine folder on it.
• When asked, type the NAS user name and password you made earlier.
• Choose to remember the password in the Mac's keychain so it does not ask again.

The First Backup Takes a While

The very first backup copies everything on your Mac, so it can take several hours - sometimes overnight for a full laptop. This is normal, and it only happens once. Every backup after that is quick, because it copies only what changed.

You can keep using the Mac while it backs up. It runs politely in the background. It may feel a touch slower during that first big copy, and then you will never notice it again.

• Plug the Mac in by cable if you can. A wired network connection is far faster and steadier than Wi-Fi for that big first copy.
• Start it before bed. Let it run overnight and it will likely be done by morning.
• Keep the Mac awake and plugged into power so it does not sleep partway through.

How Often It Backs Up

Once running, Time Machine backs up on a gentle schedule all on its own. You never press a button, and you never pick a time.

This layering is clever. Recent changes are saved often, so you can undo a mistake from an hour ago. Older history is kept less often, so it does not eat all the space. As the drive fills, Time Machine automatically thins the oldest weekly copies to make room - a process it handles without asking you.

• Hourly backups for the past 24 hours.
• Daily backups for the past month.
• Weekly backups for all previous months, as far back as space allows.

Encrypting the Backup With a Password

Encryption scrambles your backup so that only someone with the password can read it. It is a smart choice, because a backup holds copies of everything - your photos, your documents, your emails.

The backup sits on the NAS as a big file. If someone ever got hold of the NAS drives, an unencrypted backup could be read on another computer. An encrypted backup is just scrambled nonsense without the password. For anything private, that peace of mind is worth it.

• When you add the backup disk, the Mac offers a checkbox to Encrypt Backups.
• You set a password just for the backup - separate from your Mac login.
• The Mac scrambles everything as it saves it. You do not have to do anything after that.

Restoring a Single File

This is the everyday magic of Time Machine. Deleted a file by mistake? Changed a document and wish you had not? You can step back in time and pull out the version you want.

The file reappears right where it belongs, as it was on that date. Your current files are left alone - you are only adding back what you asked for.

• Open the folder where the file used to be - say, your Documents folder.
• Click the Time Machine icon in the menu bar and choose Enter Time Machine (or open it from System Settings).
• You will see your folder stacked back through time, like a deck of cards.
• Use the arrows or the timeline on the edge to travel back to when the file was there.
• Click the file to select it, then click Restore.

A Full Restore: Getting a Whole Mac Back

If a Mac dies or is replaced, your NAS backup can bring it all back - your files, your apps, your settings - onto the new or repaired machine. There are two common ways.

When you first turn on a new Mac, it offers to bring your things over using Migration Assistant. Choose to move from a Time Machine backup, point it at your NAS folder, sign in with the NAS user, and it copies everything across.

Backing Up More Than One Mac

One of the nicest things about using the NAS is that it can back up several Macs at once. A household with two or three Macs can point them all at the same NAS.

The NAS keeps the backups from mixing together. Your Mac restores only your files, and another person's Mac restores only theirs.

• Each Mac gets its own separate space inside the backup folder automatically.
• It is cleanest to give each Mac its own NAS user account - one for each person.
• Set a quota per Mac so one machine cannot swallow all the room.
• Each Mac follows the same setup steps in this guide, on its own.

Leaving Enough Free Space

Backups need breathing room. A NAS crammed to the last bit cannot make new backups well, and a backup that cannot finish is not really protecting you.

Time Machine does thin old copies to make room, but it works best when there is comfortable space to work in. Think of it like a closet - it functions far better when it is not stuffed to bursting.

• Keep some free space on the NAS overall, not just inside the backup folder.
• If the drive is getting full, that is the sign it is time for bigger drives or a cleanup.
• Remember the backup folder grows over time as it keeps more history.

Fixing "Backup Disk Not Available"

Every so often the Mac shows a message that it cannot find the backup disk. It sounds alarming, but it is usually a small hiccup, not a lost backup. Here is how to walk through it.

In most cases one of those clears it and backups resume on their own. Your past backups are still safe on the NAS the whole time.

• Is the NAS powered on and its lights normal? A NAS that went to sleep or lost power cannot be reached.
• Are the Mac and NAS on the same home network? A guest Wi-Fi or a network change can hide the NAS.
• Restart the Mac - this reconnects to the NAS more often than you would expect.
• In Time Machine settings, remove the backup disk and add it again, signing in with the NAS user.
• Check that SMB is still turned on in the NAS Control Panel.

Wired vs Wi-Fi for Reliability

Time Machine works over both Wi-Fi and a network cable. Both are fine for day-to-day backups, but a wire is steadier - and for the big first backup, it makes a real difference.

A common, comfortable pattern is this: plug the Mac in by cable for the first full backup, then unplug and let the small daily backups happen over Wi-Fi. If your Wi-Fi is weak where the Mac usually sits, backups may stall - and that is often a sign to improve the Wi-Fi.

Checking the Backup Is Really Running

A backup you never check is a leap of faith. It only takes a moment to confirm it is truly working, and doing so now and then brings real peace of mind.

The surest check is to actually restore a file, as we covered earlier. If you can pull an old file back out, you know the backup is real and readable - not just a hopeful icon on the screen.

• Open Time Machine settings on the Mac - it shows the date and time of the last successful backup.
• If the newest backup is recent, you are in good shape.
• If the last backup is days or weeks old, something needs attention.
• Turn on the Time Machine menu-bar icon so you can see its status at a glance.

What Time Machine Does NOT Cover

Time Machine is excellent at what it does, but it is not a cure for everything. Knowing its limits keeps you from a false sense of safety.

• It is not offsite. A backup on the NAS in your house does not survive a fire, flood, or theft that takes the whole house.
• It is not for phones directly. Time Machine backs up Macs. iPhones and iPads back up a different way, through iCloud or by syncing.
• It is not the same as a cloud service. It does not sync files between devices the way iCloud or Dropbox do; it makes point-in-time copies.
• It cannot restore what it never saw. A file created and deleted between backups may not be captured.

A Simple Mac Backup Routine

You do not need a complicated plan. Once Time Machine is pointed at the NAS, most of the work happens on its own. Here is a gentle routine that keeps you covered without any fuss.

• Once: set up the NAS folder, user, quota, and Time Machine as in this guide.
• Daily: nothing - the Mac backs up on its own.
• Monthly: glance at the last-backup date and the NAS free space.
• Twice a year: restore a test file to be sure the backup is readable.
• Ongoing: keep an offsite copy too, so you are covered even if the house is not.

What's in the 27-page PDF

• Why the NAS makes a great home for Mac backups
• What to set up on the Synology side, in plain steps
• How to point Time Machine at the NAS on your Mac
• Restoring one file, or your whole Mac, when you need to
• Keeping backups healthy: space, quotas, and wired connections
• The honest limits of Time Machine and what it does not cover

Why I wrote this

I write these as printable handouts because a guide you can keep in a drawer beats a web page you have to find again. No jargon, no judgment, no rushing. If you'd rather have someone sit beside you and go through it together, that's a flat $99 first visit with the 30-day follow-up included — serving Portage County from Atwater, Ohio. — Bill