Re: A syscall for changing birth time

[David Laight <david.laight.linux@gmail.com>]

On Mon, 10 Mar 2025 09:58:28 -0400
"Theodore Ts'o" <tytso@mit.edu> wrote:

> On Mon, Mar 10, 2025 at 07:26:00AM +0000, Artem S. Tashkinov wrote:
> > 
> > Why is it that the Linux kernel supports reading btime, but there's no
> > syscall to change it? At least for ext4 there's the debugfs utility, but
> > for other filesystems there's just nothing. And even debugfs is not a
> > solution, since it requires root privileges and an unmounted/mounted RO
> > filesystem.  
> 
> POSIX and Single Unix Specification also doesn't provide a way to
> allow userspace to set ctime (inode change time).  That's because the
> definition of "change time" is defined to include the time to change
> anything about the inode metadata --- including the inode timestamps.
> 

I'm sure that hadn't used to be the case.
But as some point the 'ctime' changed from something that was usually
the file create time (for some definition of create) to a pretty useless
time that is almost a waste of disk space.

	David