Read a Raspberry Pi SD card on a Mac: get files off the ext4 partition

Why you only see a small volume

A standard Raspberry Pi OS SD card is partitioned into:

• a small boot partition (called boot or bootfs), formatted FAT32, which macOS and Windows can read; and
• a large root partition (rootfs), formatted ext4, which holds /home, /etc, your projects, scripts and logs.

macOS has no ext4 support, so it either ignores the second partition or shows “The disk you inserted was not readable by this computer”. Click Ignore. If you click Initialize, you erase the card. Windows does the same, with “You need to format the disk” for the ext4 part. See “The disk you inserted was not readable”: click Ignore, not Initialize.

Check the card is intact

These only look:

1. Plug the card into a reader. In Terminal, run diskutil list. A healthy Pi card typically shows a FAT32 partition and a Linux Filesystem partition.
2. In Disk Utility, choose View > Show All Devices. You should see the card and both partitions, the second one greyed out.
3. If the card doesn’t appear at all, try a different reader and port. See SD card not reading on a Mac.

Don’t open the card in Raspberry Pi Imager, balenaEtcher or similar. They write a new image and erase the card.

Option 1: read it on a Mac with Retrova

Retrova understands ext2, ext3 and ext4 along with APFS, NTFS, FAT, exFAT, XFS and Btrfs, and it opens the card read-only. It doesn’t mount or repair the partition.

1. Insert the card and open Retrova. Choose A drive won’t open.
2. Pick the large partition labelled ext4 (rootfs). macOS asks for your administrator password; Retrova uses it only to read.
3. Browse the folders. Look in /home/pi (or your username) for projects and files, /etc for configuration, /var/www for web files, and /var/log for logs. Select what you need.
4. Choose a destination on your Mac. Retrova never writes to the card. File names that macOS or Windows can’t store are made safe for the destination.
5. Copy, then Verify. Retrova compares each copy against the original, byte for byte.

Linux permissions and ownership don’t carry over to a Mac or Windows drive, so copy what you need, not the whole system, if you only want your files. For more on reading Linux drives, see Get files off a Linux drive (ext4, XFS, Btrfs) on a Mac or Windows PC.

What is worth copying

You rarely need the whole operating system. Most people want a short list: their own files in /home/<user>; configuration such as /etc/wpa_supplicant, /etc/fstab or a Home Assistant, Pi-hole or Octoprint folder; crontab entries and scripts; web or database data under /var/www or /var/lib; and anything on the FAT32 boot partition such as config.txt and cmdline.txt. Copy those, verify, and rebuild the rest from a fresh Raspberry Pi OS image on a new card. Treat saved Wi-Fi passwords and SSH keys as secrets when you copy them.

Option 2: use a Linux machine

Any Linux PC, or a live USB, mounts ext4 natively. Plug in the card, open it in the file manager, and copy. To be careful, mount it read-only (sudo mount -o ro /dev/sdX2 /mnt, using your own device name) so nothing is written. This keeps permissions intact, which matters if you plan to put the files back onto another Pi.

If the card is corrupted or failing

SD cards in Pis suffer from power cuts and wear. If the Pi stopped booting, ext4 may need a journal replay or a repair (e2fsck), which writes. Don’t run it first. Make an image of the card, which copies the healthy data first and returns to the bad spots later, then recover from the image. See Image a failing drive on Mac or Windows. If no file system can be found on the card, Deep scan can find photos, documents and archives, but it can’t rebuild your /home tree, and names are lost.

What Retrova can’t do: it can’t undelete files with their names on APFS, ext or other file systems (only NTFS, FAT and exFAT), can’t open an encrypted drive without its password or recovery key, can’t open the startup disk of a T2 or Apple silicon Mac away from that Mac, doesn’t handle RAID sets or phones, and can’t fix a drive with physical damage. Retrova’s builds aren’t signed or notarised yet, so macOS and Windows will show a warning the first time you open it.

What not to do

Questions

Related guides

• Get files off a Linux drive (ext4, XFS, Btrfs) on a Mac or Windows PCBrowse ext4, XFS and Btrfs read-only and copy files out.
• SD card not reading on a MacReader, lock switch, format or failure: how to tell.
• Image a failing drive on Mac or WindowsA GUI way to copy a dying drive once, and when to stop.
• “The disk you inserted was not readable”: click Ignore, not InitializeWhat the Mac message means and how to keep your files.