This procedure assumes a laptop running Linux and 4 GB or larger micro SD card.
This procedure assumes the SD card is at
Download *.img.xz Ubuntu image.
Extract to SD card–This will take 5-10 minutes with a card writing at 5 MB/sec.
xz -cd BBB*-ubuntu-*armhf*.img.xz > /dev/mmcblk0
Confirm that writing to SD card is complete
then insert micro SD card into the Beaglebone Black
PLUG AN ETHERNET CABLE into your network before booting Beaglebone. Connect a monitor and keyboard to the Beaglebone.
Boot from SD card: Hold down the user/boot switch (the one closest to the microSD card on the opposite side of the PCB) and keep holding after plugging in Beaglebone power until the third LED from the Ethernet jack starts flashing (indicating the microSD is being accessed).
Wait about 1 minute. The monitor connected to the Beaglebone is black (not sleeping) during this time. Then you’ll see
ubuntu-armhf login. Login/password
After this first Ubuntu boot, you do NOT have to hold down user/boot switch on future bootups to use the SD card. Subsequent boots take me 12 seconds to get to login prompt with old Class 4 SD card.
reveals that ~ 0.5 GB is being used. Boot and run faster by copying OS from SD to internal eMMC.