Why your Rivian shows two USB drives, and how to tell them apart

Updated October 17, 2026 · by the Overlook team at CTT Apps (about us)

When a Rivian finds more than one drive it can record to, it asks which one to use and lists them as something like USB Drive (EBD1-BD08) and USB Drive (5C3A-1F70). No brand, no size, just a code. Here’s what that code is, why you might see two, and how to find out which code belongs to which drive.

What the code is

The eight characters in brackets are the drive’s volume serial number: a 32-bit number written into the filesystem when the drive is formatted. It isn’t the hardware serial number printed on the drive or reported by its USB chip, and it has nothing to do with the brand or capacity. It belongs to the format, not the device.

That has two consequences that explain most confusion:

• Formatting a drive gives it a new code. The same physical drive, formatted again on your computer or by the car, comes back as a “different” drive.
• Copying a drive byte for byte copies the code. Clone a drive with a disk-imaging tool and the two copies share one serial, so the car can’t tell them apart by name.

Formatting tools usually make the number from the date and time of formatting, so two drives formatted separately practically never match.

Why you might see two

• Two storage devices are connected: for example a hub with a stick in each port, a card reader with two slots, or a drive plus an Overlook Cache while you’re setting one up.
• One device presents two volumes: a drive with two formatted partitions, or a multi-slot reader, can show up as more than one drive.
• You reformatted the drive on a computer, so it now carries a new serial and the car treats it as a drive it hasn’t used before.

If the car records to the wrong one, Gear Guard footage ends up somewhere you aren’t looking. Picking by serial avoids that.

Where the code lives on the drive

Every FAT32 or exFAT drive starts its filesystem with a boot sector, the first 512 bytes of the partition. The serial sits at a fixed place in it, stored as four bytes with the least significant byte first:

To turn the four bytes into the code the car shows, read them backwards and split them into two groups of four hex digits:

This is exactly how the Overlook Cache works out what its drive will be called in the car: it reads its own drive image’s boot sector, finds the first partition, checks whether it’s FAT32, FAT16 or exFAT, and reads the four bytes from the right offset.

Read the serial on your computer

Windows

Open Command Prompt and run vol with the drive letter:

C:\> vol E:
 Volume in drive E is android
 Volume Serial Number is EBD1-BD08

That’s the same code, in the same format, the car shows.

Linux

lsblk or blkid show it as the filesystem’s UUID; for FAT and exFAT that UUID is the volume serial:

$ lsblk -o NAME,SIZE,FSTYPE,LABEL,UUID
sdb      238.5G
└─sdb1   238.5G exfat  android  EBD1-BD08

Mac

Finder and Disk Utility don’t show the serial in the form the car uses. You can read the boot sector directly in Terminal. First find the drive’s identifier:

diskutil list external

Say the partition is disk4s1. Then, for exFAT:

sudo dd if=/dev/rdisk4s1 bs=512 count=1 2>/dev/null | xxd -s 0x64 -l 4

and for FAT32 use -s 0x43 instead. The output is four bytes, such as 08bd d1eb; read them backwards in pairs to get EBD1-BD08. diskutil info disk4s1 tells you which format the drive is (look for “File System Personality”). Terminal may need Full Disk Access in System Settings to read the raw disk. Reading is harmless; just be careful never to swap if= and of= in a dd command.

With an Overlook Cache

The Cache does this for you. Its status page, your account page and the Overlook app show In your Rivian: USB Drive (EBD1-BD08), the exact line to pick in the car. The code changes whenever the Cache’s drive is formatted (for example with Prepare the drive for the car), and the Cache picks up the new one within a minute.

The Cache also introduces itself to the car as an “Overlook Cache” device rather than a generic Linux gadget, but the car’s list goes by the volume serial, so the code is what you’ll match on.

Example: swapping a USB drive for a Cache

Say you’ve used a USB drive for months and are replacing it with an Overlook Cache, and for a while both are connected (or the car remembers one and sees the other).

1. Before you start, read your old drive’s serial with vol, lsblk or the Mac commands above, and write it down: say 5C3A-1F70.
2. Set the Cache up and look at its status page or the app: In your Rivian: USB Drive (EBD1-BD08).
3. In the car, when it asks which USB-C drive to use, choose USB Drive (EBD1-BD08).
4. If the car offers to format the Cache’s drive, letting it is fine, but its serial will change. Check the Cache again a minute later and use the new code from then on.
5. Take the old drive out and keep it somewhere safe until anything you need from it is copied off.

The same steps work for two plain drives: read both serials on a computer first, and you’ll know which line in the car is which.

Keep it simple

• Write each drive’s serial on a label on the drive itself.
• Leave only the drive you record to plugged into the car’s data port.
• After formatting a drive on a computer, expect the car to ask again and to see a new code.
• Don’t clone one recording drive onto another; format the second one fresh instead.

Related guides

• FAT32 or exFAT for your Rivian’s USB driveThe car records to both. What actually differs, the size and speed Rivian asks for, and how to format each.
• How to watch Rivian Gear Guard footage on a Mac or PCStep by step: take the USB drive out, open it on a computer, and play every camera in sync.
• Building an Overlook Cache with a Raspberry Pi 5, with or without an NVMe SSDTwo complete builds with every part linked, assembly, setup, moving the car’s drive to the SSD, and troubleshooting.