resize2fs

Resize to maximum possible size

$ sudo resize2fs /dev/sdXN

$ sudo resize2fs -p /dev/sdXN 40G

$ sudo resize2fs -M /dev/sdXN

$ sudo resize2fs -f /dev/sdXN

resize2fs [-fFpPMbs] [-d debug-flags] [-S RAID-stride] device [size]

resize2fs resizes ext2, ext3, or ext4 filesystems. It can grow or shrink the filesystem. Note that it does not resize the underlying partition; use a partitioning tool for that.

-b

Enable 64-bit block numbers

Enable debugging output

Force resize even with errors

Flush buffer cache before resize

Shrink to minimum size

Show progress bar

Print minimum size and exit

Disable 64-bit block numbers

Specify RAID stride for optimal placement

Size can be specified as number of blocks, or with suffixes:
s: 512-byte sectors
K: Kilobytes
M: Megabytes
G: Gigabytes

Shrinking a filesystem requires it to be unmounted. Growing a filesystem can often be done while mounted (online resize) for ext3/ext4. Always resize the partition before growing or after shrinking the filesystem.

resize2fs is part of e2fsprogs. Online resize capability was added in ext3 and improved in ext4.

e2fsck(8), tune2fs(8), fdisk(8), parted(8)