Ubuntu – How to change default file/folder permission of specific user

In the .profile of that user or in the global /etc/profile, put

umask 027

Note to self: to get the umask, subtract the desired directory octal permissions from 777, so in that case 777-750 becomes 027. This should give drwxr-x---.

With that umask, the file creation mask will be 666-027 = 640 (note that this is not real subtraction, you subtract digit by digit); this will give -rw-r-----.

In short: you can read, write and change into directories; group can read and change into directories; anyone else is blocked. Is that correct?

The partition where you install ubuntu is inside windows partition which is your host and it uses ntfs file system. So, you can't use chown, chmod and chgrp command to change the file permission.

Don't be dis-hearted just change one line in the file /etc/default/grub

From :- GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

To :- GRUB_CMDLINE_LINUX_DEFAULT="rootflags=umask=002,uid=1000,gid=1000 quiet splash"

After you make the changes save the file, you need to run

sudo update-grub

afterwards to update /boot/grub/grub.cfg

WARNING: These changes give you full access to all your files on your host, including system files and it is very very dangerous, so make sure to stay away from system folders ie. your windows system and only try this when you really really need to

For reference you may visit Changing file permission on host in Wubi & How to change file permissions of host in Wubi?