Setting creation or change timestamps

Question

Using utimes, futimes, futimens, etc., it is possible to set the access and modification timestamps on a file.

Modification time is the last time the file data changed. Similarly, "ctime" or change time, is the last time attributes on the file, such as permissions, were changed. (Linux/POSIX maintains three timestamps: mtime and ctime, already discussed, and 'atime', or access time.)

Is there a function to set change timestamps? (Where "change" is the attribute modification or 'ctime', not modification time 'mtime'.) (I understand the cyclic nature of wanting to change the change timestamp, but think archiving software - it would be nice to restore a file exactly as it was.)

Are there any functions at all for creation timestamps? (I realize that ext2 does not support this, but I was wondering if Linux did, for those filesystems that do support it.)

If it's not possible, what is the reasoning behind it not being so?

Answer 1

For ext2/3 and possibly for ext4 you can do this with debugfs tool, assuming you want to change the ctime of file /tmp/foo which resides in disk /dev/sda1 we want to set ctime to 201001010101 which means 01 January 2010, time 01:01:

Warning: Disk must be unmounted before this operation

# Update ctime debugfs -w -R 'set_inode_field /tmp/foo ctime 201001010101' /dev/sda1  # Drop vm cache so ctime update is reflected echo 2 > /proc/sys/vm/drop_caches 

Information taken from Command Line Kung Fu blog.