When GUI file manager in Ubuntu cannot find the disc image on bootable SD card

This happens quite often.
The GUI file manager is mounting the partition of the SD card, but the underlying block device might have a different name than expected.

Let’s carefully locate it:

🧭 1. Check again with lsblk after inserting the card

First, remove the card if it’s inserted.
Run:

lsblk

Now insert the SD card again and run:

lsblk

Compare the two outputs — the new device that appears is your SD card.
Typical names:

• mmcblk0 (common for internal card readers)
• sdb or similar (USB SD reader)
• nvme... (rare, but possible on some systems)

🪛 2. Alternatively use dmesg (logs)

Right after inserting the card, run:

dmesg | tail -20

Look for lines like:

[12345.678901] mmc0: new SDHC card at address 0001

[12345.679123] mmcblk0: mmc0:0001 SD32G 29.7 GiB

[12345.679456]  mmcblk0: p1

or

[12345.678901] sd 3:0:0:0: [sdb] 31293440 512-byte logical blocks

[12345.678923]  sdb: sdb1

→ This will tell you the exact device name (e.g. /dev/mmcblk0 or /dev/sdb).

🪣 3. Use ls /dev to verify

Once you have a clue from dmesg, check:

ls /dev/mmcblk*

or

ls /dev/sd*

You should see something like /dev/mmcblk0 and /dev/mmcblk0p1.

🧼 4. If it still doesn’t appear

If nothing new shows up:

• The card reader may require extra drivers.
• Or the SD card is mounted as a GVFS (user-space) volume rather than a raw block device — which means dd can’t access it directly.

You can check that with:

mount | grep gvfs

If it’s mounted like:

gvfsd-fuse on /run/user/1000/gvfs

then your system is not exposing the SD card as a raw block device.

👉 Fix: Use a different SD card reader (USB adapter) that presents the card as /dev/sdX or /dev/mmcblk0. Internal laptop readers sometimes don’t.

✅ Once you have the device name

Then you can run:

sudo umount /dev/DEVICE*

sudo dd if=/dev/DEVICE of=/dev/sdY bs=4M status=progress conv=fsync

(Replace DEVICE with your SD card name and sdY with your USB stick.)