"Create a new file system on the block device:
mke2fs $BLK_DEV
mount $BLK_DEV /mnt
mkdir /mnt/root
cd /mnt/root
Find the Debian mirror that is nearest to you (in terms of network connectivity), and set the variable DEBIAN_MIR to contain the URL of this mirror (including the trailing /debian). Browse the sub-URL pool/main/d/debootstrap under $DEBIAN_MIR to locate a recent version of debootstrap, and let DEBOOTSTRAP_URL contain the full URL for this version."