How to increase the size?

Question

linux

How to increase the size of the partition / (/dev/sda3)
Was

df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 1.1T 1.4G 1.1T 1% /
tmpfs 34G 0 34G 0% /dev/shm
/dev/sda2 1.1G 79M 925M 8% /boot
/dev/sda5 1.3T 209M 1.2T 1% /home

Became after size reduction

umount /home
resize2fs /dev/sda5 20G
mount /home
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 1008G 1.2G 956G 1% /
tmpfs 32G 0 32G 0% /dev/shm
/dev/sda2 1008M 76M 882M 8% /boot
/dev/sda5 20G 172M 19G 1% /home

But the increase is not possible

resize2fs /dev/sda3
resize2fs 1.41.12 (17-May-2010)
The filesystem is already 268435456 blocks long. Nothing to do!

Answer 1

I understand you want to reallocate free space.
The increase fails because the /dev/sda3 partition remains the same as it was.
You only reduced the size of the file system, and then you need to:
1. Reduce the size of the /dev/sda5 partition using fdisk/parted
2. Increase the size of the /dev/sda3 partition
3. Increase the size of the file system on /dev/sda3
Note that sda5 is most likely comes after sda3, so you need to resize sda5 on the left.