format

I recently pulled a SATA hard drive out of a Linux box that I wanted to grab some files off of. I only had my Mac on hand, and I had a USB 3.0 to SATA hard drive adapter at the ready.

But when I plugged in the hard drive, macOS said it couldn't recognize the disk.

Makes sense, because macOS includes support for Apple's filesystems, not Linux (or even NTFS, Windows' preferred filesystem). There are commercial solutions you can buy, like Paragon Software's extFS for Mac, but that costs $39, and I don't want to deal with the licensing issues that may exist there if I just want to grab a few files off one hard drive.

Luckily, there are some open source libraries that allow at least read only access to ext4-formatted disks on macOS. Let's install them and use them to mount the drive:

First, install macfuse, using homebrew:

This is a simple guide, part of a series I'll call 'How-To Guide Without Ads'. In it, I'll show you how I completely initialize a hard drive so I can re-use it somewhere else (like Ceph) that doesn't like drives with partition information!

First, a warning: this blog post does not show how to zero a hard drive, or secure erase. That's a slightly different process.

But as someone with way too many storage devices (from testing, mostly), I find myself in the position of trying to use a spare drive in some place where it expects a brand new drive, but winds up failing because the drive had a partition, or had valid boot files from an SBC or something.

I wanted to document the easiest way in Linux to completely reset a hard drive—at least from Linux's perspective.

The impetus was when I was trying to get some hard drives added to a Ceph OSD, and the process that tried adding them ran into an error stating RuntimeError: Device /dev/sda has partitions.

This is a simple guide, part of a series I'll call 'How-To Guide Without Ads'. In it, I'm going to document how I partition, format, and mount a large disk (2TB+) in Linux with parted.

Note that newer fdisk versions may work better with giant drives... but since I'm now used to parted I'm sticking with it for the foreseeable future.

List all available drives

$ sudo parted -l
...
Error: /dev/sda: unrecognised disk label
Model: ATA Samsung SSD 870 (scsi)                                         
Disk /dev/sda: 8002GB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags:

Good, I had plugged in that SSD just now, and it's brand new, so it doesn't have a partition table, label, or anything. It's the one I want to operate on. It's located at /dev/sda. I could also find that info with lsblk.

tl;dr: If you see weird errors when using or formatting a drive internally on a Mac (especially after upgrading to a newer and/or faster SATA hard drive), it could mean the SATA cable needs to be replaced.

Who would've thought such a tiny cable could cause so many problems?

I have an older Mac mini (mid-2011 i5 model), and I use it as a general media server and network backup. It handles Time Machine backups for two other Macs, it has about 20 TB of external storage connected, and I also use it as a 'home base' to store all my Dropbox, iCloud, and Photos content locally, and store an extra Time Machine backup of all that. I'm a little nutty about backups... but I haven't lost a file in two decades and I don't want to start now ;-).

To use eMMC modules on the Orange Pi, Radxa, Milk-V, etc. as a writable volume in Linux, you need to delete the existing partitions (on my old Orange Pi, it was formatted as FAT/WIN32), create a new partition, format the partition, then mount it:

1. Delete the existing partitions, and create a new partition:
   1. sudo fdisk /dev/mmcblk1
   2. p to list all partitions, then d and a number, once for each of the existing partitions.
   3. n to create a new partition, then use all the defaults, then w to write the changes.
2. Format the partition: sudo mkfs.ext4 -L "emmc" /dev/mmcblk1p1
3. Create a mount point: sudo mkdir -p /mnt/emmc
4. Mount the disk: sudo mount /dev/mmcblk1p1 /mnt/emmc

Note your eMMC device may be a different ID, e.g. mmcblk2 or mmcblk0, depending on the order the board firmware loads multiple devices in. Check with lsblk to see which device you would like to modify.

I thought I'd post my experience here, for the benefit of others, because I couldn't find a whole lot of information about this specific use of an external USB flash drive.

I have a MacBook Air with a dainty 128GB SSD drive, so I try to keep large files that I rarely use on external drives. I have plenty of external USB and FireWire storage (over 6 TB), and running VMs in either Parallels or VMWare Fusion works great (very highly performant) off any of these external drives.

However, there's no way I'm going to lug around an external hard drive and USB cable (and maybe power adapter) just so I can test things in Internet Explorer (basically, the only use I have for Windows).

Flash Drive to the Rescue!

I found a cheap 32GB USB flash drive that only sticks out of my MacBook Air half an inch, and copies at a consistent rate of 30MB/second (which is quite sufficient for most tasks). Also, the little drive should have very good read performance, since it's not a spinning platter. Write speed wouldn't be anything to brag about, but writing shouldn't happen all that often when simply opening up Internet Explorer—I hope!