Write USB¶

The stick will be wiped. Confirm the device is a removable USB — never your internal NVMe/SATA disk.

This page’s Linux path matches an evidence pass that wrote ubuntu-24.04.5-live-server-amd64.iso with dd. Sample output uses a ~29 GB stick at /dev/sda labelled USB DISK 2.0; your device letter and size will differ.

1. Detect the USB¶

Plug the stick in, then:

lsblk -o NAME,SIZE,TYPE,FSTYPE,LABEL,MODEL,TRAN,RM

NAME          SIZE TYPE FSTYPE LABEL       MODEL                   TRAN   RM
sda          28.9G disk                    USB DISK 2.0            usb     1
└─sda1       28.9G part vfat   UBUNTU 24_0                                 1
nvme0n1     931.5G disk                    Samsung SSD …           nvme    0
├─nvme0n1p1     1G part vfat                                       nvme    0
└─nvme0n1p2 930.5G part ext4                                       nvme    0

Read the row with TRAN=usb and RM=1. That whole disk is the target (example /dev/sda). The internal OS disk stays on nvme / sata with RM=0 — do not use that for of=.

Optional: confirm by-id symlink:

ls -l /dev/disk/by-id/usb*

… usb-_USB_DISK_2.0_…-0:0 -> ../../sda
… usb-_USB_DISK_2.0_…-0:0-part1 -> ../../sda1

2. Safety gate (recommended)¶

Refuse to write unless the candidate is still a removable USB disk:

eval "$(lsblk -P -o NAME,SIZE,TYPE,MODEL,TRAN,RM /dev/sda | head -1)"
echo "NAME=$NAME SIZE=$SIZE TYPE=$TYPE MODEL=$MODEL TRAN=$TRAN RM=$RM"
test "$TRAN" = "usb" && test "$RM" = "1" && test "$TYPE" = "disk" \
  && echo "safe_to_flash" || echo "REFUSE"

NAME=sda SIZE=28.9G TYPE=disk MODEL=USB DISK 2.0 TRAN=usb RM=1
safe_to_flash

If you see REFUSE, stop and re-check lsblk.

3. Unmount if needed¶

sudo umount /dev/sda1 2>/dev/null || true
findmnt /dev/sda /dev/sda1 || echo "not mounted"

not mounted

4. Write the ISO with `dd`¶

Use the whole disk (/dev/sda), not a partition (/dev/sda1). Path assumes the ISO from Download ISO:

ISO="$HOME/Downloads/ubuntu-24.04.5-live-server-amd64.iso"
sudo dd if="$ISO" of=/dev/sda bs=4M status=progress oflag=sync

4076863488 bytes (4.1 GB, 3.8 GiB) copied, 623 s, 6.5 MB/s
972+1 records in
972+1 records out
4080486400 bytes (4.1 GB, 3.8 GiB) copied, 622.851 s, 6.6 MB/s

Then flush caches:

sync
echo synced

synced

Password prompt

dd to a block device needs root. Run it in a normal terminal so sudo can prompt. Agent/CI shells without a TTY cannot enter that password for you.

balenaEtcher (optional)

If you prefer a GUI: balenaEtcher → select the ISO → select the USB → Flash. Still confirm you picked the stick, not the system drive.

5. Confirm the stick looks like an installer¶

After a successful write, the hybrid ISO layout appears (evidence pass):

lsblk -o NAME,SIZE,TYPE,FSTYPE,LABEL,TRAN,RM /dev/sda

NAME    SIZE TYPE FSTYPE  LABEL                           TRAN RM
sda    28.9G disk iso9660 Ubuntu-Server 24.04.5 LTS amd64 usb   1
├─sda1  3.8G part iso9660 Ubuntu-Server 24.04.5 LTS amd64       1
├─sda2    5M part vfat    ESP                                   1
└─sda3  300K part                                               1

You should not still see a single large vfat volume labelled UBUNTU 24_0 — that was the old contents before dd.

Eject before moving the stick to the target machine:

sudo eject /dev/sda || true
echo ready_to_boot

ready_to_boot

Next¶

Install — boot the target machine from this USB.