# df
Filesystem     1K-blocks     Used Available Use% Mounted on
devtmpfs          991664       56    991608   1% /dev
tmpfs            1002248        0   1002248   0% /dev/shm
/dev/nvme0n1p1  20509288 20154008    255032  99% /

# growpart /dev/nvme0n1 1
CHANGED: disk=/dev/nvme0n1 partition=1: start=4096 old: size=41938910,end=41943006 new: size=83881950,end=83886046

# resize2fs /dev/nvme0n1p1
resize2fs 1.43.5 (04-Aug-2017)
Filesystem at /dev/nvme0n1p1 is mounted on /; on-line resizing required
old_desc_blocks = 2, new_desc_blocks = 3
The filesystem on /dev/nvme0n1p1 is now 10485243 (4k) blocks long.

# df -h
Filesystem      Size  Used Avail Use% Mounted on
devtmpfs        969M   56K  969M   1% /dev
tmpfs           979M     0  979M   0% /dev/shm
/dev/nvme0n1p1   40G   20G   20G  50% /