Changing Ownership: "Operation not permitted" - even as root!

Question

I am trying to help a user solve an issue with a bootable USB drive, but there seems to be a file whose ownership cannot be edited. I thought it would have been possible with:

sudo chown user:user ldlinux.sys

When that is executed, however, terminal gives this error:

Operation not permitted

The extended chat I had with the user can be found here.

Solution

Probably the file has the immutable flag set in its extended attributes:

user@user-X550CL ~/tmp % touch immutable
user@user-X550CL ~/tmp % sudo chown root:root immutable
[sudo] password for user:
user@user-X550CL ~/tmp % sudo chattr +i immutable
user@user-X550CL ~/tmp % lsattr immutable
----i--------e-- immutable
user@user-X550CL ~/tmp % sudo chown user:user immutable
chown: changing ownership of 'immutable': Operation not permitted

To fix this, just run sudo chattr -i file:

user@user-X550CL ~/tmp % sudo chattr -i immutable
user@user-X550CL ~/tmp % lsattr immutable
-------------e-- immutable
user@user-X550CL ~/tmp % sudo chown user:user immutable
user@user-X550CL ~/tmp % 

Comments

[Byte Commander]

Maybe checking ACLs is an option? I commented on the original question and asked for the output of getfacl ldlinux.sys

[muru]

I think the USB is mounted read-only. Ask OP to check mount options via mount.

[userDepth]

AFAIK it is (users:username) not just the user

[gaoithe]

users:username ?? it is user:group

[A.B.]

Thanks for the explanation. I forget it again and again. ;)

[TenLeftFingers]

I get: chattr: Inappropriate ioctl for device while reading flags on 64GB, while trying this on a usb thumb drive at /media/

[Jonathan Parent Lévesque]

For me, the "a" (Append only) flag was the problem. sudo chattr -a fileName solved the problem.

[Brent Faust]

+1, but fails for some files (not just symlinks), even running as root sudo chattr -i returning chattr: Operation not supported while reading flags.

[harperville]

My USB has msdos filesystem. Found this: unix.stackexchange.com/questions/552121/… so I went ahead and reformatted as ext4 per askubuntu.com/questions/149984/…

[sonrad10]

You get the Operation not supported error when trying to mount a Windows filesystem (exFat/NTFS) with incorrect mount options. You can either reformat your drive to ext4, or simply change the mount options with this answer: askubuntu.com/a/956072/612853

[linstar]

Thanks kos, this solved it for me just now.. But, man chattr doesn't even list -i as an option! So, thanks again.