USB Flash Drive Handling

Created: · 1 min read
usb, mount, cheat-sheet

Now I want to manually mount, write to, and manage USB flash drives. Auto-mount will be disabled. Below is a memo explaining how to do it.

Detection vs Mounting vs Permissions

Layer Symptom Meaning
Detection no /dev/sdX hardware / driver issue
Mount device exists, not accessible not mounted
Permissions “Permission denied” wrong mount options

Diagnostics

Check device

lsblk

Check filesystem

blkid

Check kernel messages

dmesg | tail

Check read-only flag

cat /sys/block/sda/ro

Correct Workflow

Detect device

lsblk

Example:

sda      58.6G
└─sda1   58.6G

If ISO image → reformat

doas umount /mnt/usb   # must not be inside mount dir
doas wipefs -a /dev/sda
doas fdisk /dev/sda

Inside fdisk:

o   # new partition table
n   # new partition
w   # write

Format

exFAT:

doas mkfs.exfat /dev/sda1

Mount with correct permissions

doas mount -t exfat -o uid=$(id -u),gid=$(id -g) /dev/sda1 /mnt/usb

Use

touch /mnt/usb/testfile
ls /mnt/usb

Unmount

cd ~
doas umount /mnt/usb