Home » Birth is empty on ext4

Birth is empty on ext4


The field gets populated (see below) only coreutils stat does not display it. Apparently they’re waiting1 for the xstat() interface.

coreutils patches – aug. 2012 – TODO

stat(1) and ls(1) support for birth time. Dependent on xstat() being
provided by the kernel

You can get the creation time via debugfs:

debugfs -R 'stat <inode_number>' DEVICE

e.g. for my /etc/profile which is on /dev/sda2 (see How to find out what device a file is on):

stat -c %i /etc/profile
debugfs -R 'stat <398264>' /dev/sda2
debugfs 1.42.5 (29-Jul-2012)
Inode: 398264   Type: regular    Mode:  0644   Flags: 0x80000
Generation: 2058737571    Version: 0x00000000:00000001
User:     0   Group:     0   Size: 562
File ACL: 0    Directory ACL: 0
Links: 1   Blockcount: 8
Fragment:  Address: 0    Number: 0    Size: 0
 ctime: 0x506b860b:19fa3c34 -- Wed Oct  3 02:25:47 2012
 atime: 0x50476677:dcd84978 -- Wed Sep  5 16:49:27 2012
 mtime: 0x506b860b:19fa3c34 -- Wed Oct  3 02:25:47 2012
crtime: 0x50476677:dcd84978 -- Wed Sep  5 16:49:27 2012
Size of extra inode fields: 28

Time fields meaning:

  • ctime: file change time.
  • atime: file access time.
  • mtime: file modification time.
  • crtime: file creation time.

1 Linus’ reply on LKML thread

I combined this into a simple shell function:

get_crtime() {
  for target in "${@}"; do
    inode=$(stat -c %i "${target}")
    fs=$(df  --output=source "${target}"  | tail -1)
    crtime=$(sudo debugfs -R 'stat <'"${inode}"'>' "${fs}" 2>/dev/null | 
    grep -oP 'crtime.*--s*K.*')
    printf "%st%sn" "${target}" "${crtime}"

You can then run it with

$ get_crtime foo foo/file /etc/
foo Wed May 21 17:11:08 2014
foo/file    Wed May 21 17:11:27 2014
/etc/   Wed Aug  1 20:42:03 2012

The xstat function never got merged into mainline. However, a new statx call was proposed later on, and was merged in Linux 4.11. The new statx(2) system call does include a creation time in its return struct. A wrapper for statx(2) was added to glibc only in 2.28 (release August 2018). And support for using this wrapper was added in GNU coreutils 8.31 (released March 2019):

stat now prints file creation time when supported by the file system,
on GNU Linux systems with glibc >= 2.28 and kernel >= 4.11.

% stat --version
stat (GNU coreutils) 8.31
Copyright (C) 2019 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Michael Meskes.
% stat /
  File: /
  Size: 4096            Blocks: 8          IO Block: 4096   directory
Device: b302h/45826d    Inode: 2           Links: 17
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2019-06-06 20:03:12.898725626 +0900
Modify: 2019-05-28 05:15:44.452651395 +0900
Change: 2019-05-28 05:15:44.452651395 +0900
 Birth: 2018-06-07 20:35:54.000000000 +0900

What follows is a demo of statx where userland has yet to catch up (older glibc or coreutils). It’s not easy to call system calls directly in a C program. Typically glibc provides a wrapper that makes the job easy, but Luckily, @whotwagner wrote a sample C program that shows how to use the statx(2) system call on x86 and x86-64 systems. Its output is the same format as stat‘s default, without any formatting options, but it’s simple to modify it to print just the birth time. (If you have a new enough glibc, you won’t need this – you can use statx directly as described in man 2 statx).

First, clone it:

git clone https://github.com/whotwagner/statx-fun

You can compile the statx.c code, or, if you just want the birth time, create a birth.c in the cloned directory with the following code (which is a minimal version of statx.c printing just the creation timestamp including nanosecond precision):

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>
#include "statx.h"
#include <time.h>
#include <getopt.h>
#include <string.h>

// does not (yet) provide a wrapper for the statx() system call
#include <sys/syscall.h>

/* this code works ony with x86 and x86_64 */
#if __x86_64__
#define __NR_statx 332
#define __NR_statx 383

#define statx(a,b,c,d,e) syscall(__NR_statx,(a),(b),(c),(d),(e))

int main(int argc, char *argv[])
    int dirfd = AT_FDCWD;
    int flags = AT_SYMLINK_NOFOLLOW;
    unsigned int mask = STATX_ALL;
    struct statx stxbuf;
    long ret = 0;

    int opt = 0;

    while(( opt = getopt(argc, argv, "alfd")) != -1)
        switch(opt) {
            case 'a':
                flags |= AT_NO_AUTOMOUNT;
            case 'l':
                flags &= ~AT_SYMLINK_NOFOLLOW;
            case 'f':
                flags &= ~AT_STATX_SYNC_TYPE;
                flags |= AT_STATX_FORCE_SYNC;
            case 'd':
                flags &= ~AT_STATX_SYNC_TYPE;
                flags |= AT_STATX_DONT_SYNC;

    if (optind >= argc) {

    for (; optind < argc; optind++) {
        memset(&stxbuf, 0xbf, sizeof(stxbuf));
        ret = statx(dirfd, argv[optind], flags, mask, &stxbuf);
        if( ret < 0)
            return EXIT_FAILURE;
        printf("%lld.%un", *&stxbuf.stx_btime.tv_sec, *&stxbuf.stx_btime.tv_nsec);
    return EXIT_SUCCESS;


$ make birth
$ ./birth ./birth.c
$ ./birth ./birth.c | xargs -I {} date -d @{}
Mon Nov 27 14:34:51 UTC 2017

In theory this should make the creation time accessible on more filesystems than just the ext* ones (debugfs is a tool for ext2/3/4 filesystems, and unusable on others). It did work for an XFS system, but not for NTFS and exfat. I guess the FUSE filesystems for those didn’t include the creation time.

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