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I just installed Ubuntu 18.04 as a second OS in my Acer notebook, (alongside with Windows 10) using 2 partitions, / and /home (sda5 and sda6). However, I found that I might have reserved less space than I'd have liked. So I was pretending to reinstall it.

Is it safe to just format both partitions from the Live USB, free some more from the Windows partition (sda3) using Windows' Disk Manager (already freed 40 GB) and create 2 new partitions with the allocated space distributed correctly? Is it possible that Grub2 will break after it?

GParted screenshot

marked as duplicate by karel, Fabby, user535733, MadMike, N0rbert Aug 30 '18 at 19:02

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  • It is safe, meaning nothing is likely to explode as an aftermath. Grub will be reinstalled along with the OS, which should not break anything. – mikewhatever Aug 26 '18 at 21:24
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    If you don’t want to reinstall Ubuntu for another reason, reinstalling is not necessary to resize partitions. You should be safe with just doing a backup (preferably the whole disk) and then resize using live GParted. – Melebius Aug 28 '18 at 8:03

Essentially yes, it is safe. However, you still should make sure your personal data are backed up, because there is always a risk that something goes wrong during the manipulations of partitions, either through human error or a hardware or software problem.

The approach you propose is essentially OK, except that there is no need to format both partitions first because you will be deleting them to free the space for two new partitions.

You can do everything from the Ubuntu partitioning gparted, from which you showed a screenshot. Alternatively, you may change the partitions from within the Ubuntu Installer (after choosing "something else").

Before you start, make sure all partitions are properly closed. This implies that you need to fully shut down Windows (no hibernate!) before proceeding.

Essentially, you need to delete sda5 and sda6, then shrink sda3. Then, Ubuntu can be installed in the free space.

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