When Should You “Ignore Ownership” on an External Drive?

When Should You “Ignore Ownership” on an External Drive?

Under the hood, macOS relies on Unix, which is a multi-user operating system. That’s why a Mac can host multiple users who, as long as they don’t know each other’s passwords, cannot see each other’s files. To maintain each user’s privacy, macOS relies on permissions that specify who can do what with any given file or folder. For the most part, permissions work how they’re supposed to, letting you work with all your files and keep any other users on the Mac out of your stuff.

Where things can get tricky is with external drives. In some situations, permissions can prevent you from accessing files written to an external drive on one Mac from another Mac. That happens because the first admin user account created on a Mac is given the UniqueID of 501, regardless of its name. (Because, Unix.) If you create additional accounts, they get UniqueIDs of 502, 503, and so on. Again, the names are irrelevant; all that matters is the UniqueID.

If you write files to an external drive while logged into the 501 admin account on one Mac but then try to access those files from an account with any other UniqueID on that Mac or any other, macOS won’t let you. No 503 account, for instance, can access a 501 account’s files

There are tweaky Unix solutions to this problem, but Apple realized this would be an issue from the early days of Mac OS X and provided a single-click solution: the “Ignore ownership on this volume” checkbox. When selected, it tells macOS to pay no attention to permissions for all the files and folders on a drive, regardless of what that might mean.

To access this setting, select the drive in the Finder, choose File > Get Info, and expand the Sharing & Permissions section at the bottom. Before you can select the checkbox, click the lock icon and enter your admin password when prompted.

There are three scenarios where enabling “Ignore ownership on this volume” is helpful:

●     Multi-user access: Imagine that you share a Mac with family members or colleagues. You want to keep your email and text message conversations private but need to share numerous other large files stored on an external drive. (For just a few files, use the Shared folder alongside your user folders.) By enabling “Ignore ownership,” you can be certain that all users of the Mac can do whatever they need to with those files.

●     Access from multiple Macs: Suppose you have a portable SSD containing video files you want to display from any Mac. Perhaps they’re canned business presentations or home videos. Since you cannot know what the UniqueID of the current account on any given Mac will be, selecting “Ignore ownership” will ensure that you can open your videos regardless.

●     Juggling user accounts: Although it’s a bad idea to do this willy-nilly, some people regularly create and delete accounts for their own use. Since all the accounts are used by a single person, they don’t think about permissions as an issue, but macOS does unless they select “Ignore ownership.”

In general, when using an external drive to move files between accounts, people, or Macs, select “Ignore ownership” to prevent pesky permissions problems.

But that doesn’t mean you should turn on “Ignore ownership” in every situation. There are some situations where enabling the setting would be inappropriate because it’s essential to preserve permissions:

Boot drives:macOS itself relies on specific permissions and won’t even show the checkbox for boot drives. If you’re planning to install macOS on an external drive and use it to boot a Mac (Apple provides instructions), make sure not to select “Ignore ownership” before starting.

Time Machine drives: Time Machine cares deeply about maintaining correct permissions, so you should not enable “Ignore ownership” on a drive that you plan to use with Time Machine. After Time Machine starts backing up to a drive, the “Ignore

●     Bootable duplicates and other backups: Similarly, if you’re using Carbon Copy Cloner or SuperDuperto create a bootable duplicate of your boot drive, “Ignore ownership” must be unchecked. Retrospect also warns users to turn off “Ignore ownership” on backup and restore drives to ensure that permissions are preserved. Other backup apps likely have similar requirements.

One last thought. If you run into permissions-related problems reading files from an external drive, it’s worth enabling “Ignore ownership” to see if that resolves your issues. If it doesn’t, or if the problems keep cropping up in different contexts, contact us.

(Featured image based on an original by iStock.com/Rawpixel)

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Social Media: Permissions are an essential aspect of the Unix underpinnings in macOS, but on some external drives, they can be problematic. Learn when you should and should not enable “Ignore ownership on this volume.”

Missed an Alert? Check Notification Center

Missed an Alert? Check Notification Center

iOS, iPadOS, and macOS all let you specify whether any given app should show no notifications, temporary banners, or persistent alerts: look in Settings > Notifications and System Settings > Notifications. Temporary banners appear briefly and then automatically disappear, which is appropriate for notifications requiring no acknowledgment. But what if you see a temporary banner only as it’s disappearing and can’t read it in time? You can find a historical list of notifications in Notification Center. To open it from the Lock Screen on an iPhone or iPad, swipe up from the middle of the screen. From any other screen, swipe down from the center of the top of the screen. On the Mac, click the date and time in the upper right corner. If your Mac has a trackpad, you can also swipe with two fingers from the right edge.

(Featured image based on an original by iStock.com/Shutthiphong Chandaeng)

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Social Media: If a temporary banner disappears from your iPhone, iPad, or Mac before you have a chance to read it, you can find it in Notification Center.

It’s Usually OK to Share Full-Size Images in Email and Messages

It’s Usually OK to Share Full-Size Images in Email and Messages

In the early days of the Internet, when most people connected via slow modems, saving bandwidth was a big deal. You could watch images load on Web pages, and you’d have to wait to download a large email attachment before the rest of your email would appear. For most people, in most situations, bandwidth isn’t nearly as big of a deal anymore. The average Internet download speed in the US is nearly 250 megabits per second, such that most Web pages load instantly, email just appears, and we think nothing of having multiple video streams playing at once.

All that’s by way of saying that you don’t have to shrink images that you share in email or Messages in most cases, and doing so can cause problems for recipients. The most common issues people run into are images being too small or fuzzy to see, not matching the dimensions needed for a website, or being too low quality to save for posterity.

There are exceptions. Smaller or lower quality images may make sense when sending or receiving in rural areas with slow Internet connections, places with no Wi-Fi and tenuous cell service, and remote locations with only satellite Internet. In those cases, you’ll either realize that messages are taking a long time to send or hear from the other party that it’s a problem. But, most of the time, it’s best to send actual size images, so let’s look at how you ensure that.

Sending Actual Size Images in Email

How do you ensure you’re not sending downsized images in email? In Mail on Apple’s devices, the details vary slightly depending on which device you are using, but in each case, you want to use the Actual Size option. Neither Gmail nor Outlook suffers from this problem. Here’s what you need to know for each of these email clients:

Mail on the Mac:When you drop an image into a Mail message, an Image Size menu specifies the size at which it will be sent. Small resizes the longest side to 320 pixels, Medium to 640, and Large to 1280. Actual Size sends the original image, which is what you want. The Image Size menu remembers its setting, so if you send one image in a smaller size, you probably want to reset it to Actual Size for the next one. If you attach multiple images in a single message, they’ll all be resized similarly.

Mail on the iPad: On the iPad, when you add an image to a message, you’ll see a note in the header information that says something like “Images: 2.9 MB.” Tap anywhere in the header to reveal extra header fields, including an Image Size line with options for the different sizes. Small and Medium work as on the Mac, resizing the longest side to 320 and 640 pixels, and Actual Size sends the original, which is generally what you want. However, Large resizes the image to half the size of the original if appropriate or leaves it alone if not. Multiple images will be resized to the selected size.

Mail on the iPhone: Because of the iPhone’s smaller screen size, Mail on the iPhone asks how to resize the image(s) after you tap the send button. The results are the same as on the iPad, described above.

Gmail on the Web: You don’t need to do anything when sending images in Gmail to prevent them from being resized. Although Gmail lets you visibly resize an image with handles and offers Small, Best Fit, and Original options when you click, none of them change the file size or resolution of the image being sent. Only some receiving email apps (including Gmail and Outlook, but not Mail) will display the sent size. Regardless of the visible size, opening an attached image reveals that it’s the original. Note that Gmail has a 25 MB limit on attachments and may refuse to send a message with more than that or may resize images to make them fit. If you need to send an image at a particular size using Gmail, resize it before attaching—see below for a tip on how to do that.

Outlook on the Mac: You can visibly resize images sent in Outlook on the Mac, but doing so affects only the displayed size, not the file size or resolution of the attached image. Email clients receiving an Outlook-resized image may do so at the sent size, but opening it reveals that it’s the original image. If you need to send an image at a smaller size, resize it before sending—read below for help.

Avoiding Lower-Quality Images in Messages

Although it may seem confusing, keeping images from being resized in email is pretty straightforward. Ensuring that you send full-quality images in Messages is trickier because there are multiple variables in play:

Turn off Low Quality Image Mode:Make sure you turn off Settings > Messages > Low Quality Image Mode on the iPhone and iPad. (The Mac has no comparable setting.) This mode downsizes images sent via iMessage (blue bubble conversations), making them smaller and lower quality. Only turn it on if it’s paramount that you save bandwidth due to a slow connection or data cap.

●     Avoid sending via SMS/MMS: There’s no need for Low Quality Image Mode for messages sent via SMS (green bubble conversations) because the MMS technology used to send images for SMS conversations has size limits that vary by carrier, usually between 500 KB and 3.5 MB. Messages automatically resizes and compresses images to fit within carrier limits. You have no control over this process, which is likely to be unpredictable. If you need to send someone a full-quality image, use email instead of SMS. Happily, in iOS 18, Messages will support the RCS standard that allows full-quality images.

●     Prefer high-speed connections: Although Apple doesn’t document anything along these lines, some suggest that Messages may reduce image size or quality when using slow networks. If you (or your recipient) experience issues while using weak cellular connectivity, try again when connected to the Internet via high-speed Wi-Fi.

Bonus Tip: How to Resize an Image Manually

Let’s flip the problem around. Say you use Gmail or Outlook and need to send an image with specific dimensions or a smaller file size than the original. How do you do that easily? Preview! That’s right, Apple’s Preview works well for resizing images and shrinking file sizes.

To resize an image you have open in Preview, choose Tools > Adjust Size and enter the desired width or height into the appropriate field. As long as Scale Proportionally is selected, Preview will automatically set the other dimension to resize the image proportionally. You can choose other units, but pixels is generally best. Preview even reports on the resulting size at the bottom. After you click OK, save the image.

What if you want to reduce an image’s file size without changing its dimensions? With the image open in Preview, choose File > Export, choose JPEG from the Format menu, and move the Quality slider to the left to increase the JPEG compression. Preview reports on the new file size each time you move the slider. You’ll want to export a few tests to determine the best combination of file size and quality.

Generally speaking, changing an image’s dimensions is a better way to reduce file size than increasing compression.

But really, in most cases, just send the original image.

(Featured image by Adam Engst)

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Social Media: It’s frustrating to receive a small or fuzzy image via email or Messages. There’s no need for it in most cases, and we explain how you can be sure you’re sending full-size images.