Expand a partition and a filesystem on Debian

1. Backup the current partition table:

sh sfdisk -d /dev/sda > sda_partition_bakup.dmp

1. Get details about the changes to the partition table to apply (dry-run) to see what will be changed:

sh growpart -N /dev/sda 1

1. Apply changes to the partition table:

sh growpart /dev/sda 1

1. Resize the file system:

sh resize2fs /dev/sdb1

1. Check the file system size:

sh df -h