#> sudo wget https://apt.armbian.com/armbian.key -O key
#> sudo gpg --dearmor < key | sudo tee /usr/share/keyrings/armbian.gpg > /dev/null
#> sudo chmod go+r /usr/share/keyrings/armbian.gpg
#> sudo echo "deb [arch=$(dpkg --print-architecture) signed-by=/usr/share/keyrings/armbian.gpg] http://apt.armbian.com $(lsb_release -cs) main  $(lsb_release -cs)-utils  $(lsb_release -cs)-desktop" | sudo tee /etc/apt/sources.list.d/armbian.list
apt update

lsb_release -cs is to be replaced by distro name (a.k.a bullseye) if required.

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Learn the step by step process of how to increase a standard partition & extend root partition using fdisk online in Linux without downtime or losing data

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Once partition table is resized, resize the filesystem itself so it spreads to the extent of the enlarged partition (might be located in /sbin):
#> sudo resize2fs /dev/mmcblk1p2