File changes propagating in older snapshots: what am I doing wrong?

Matthew Dillon dillon at backplane.com
Fri Apr 7 13:09:16 PDT 2017 

The timestamps in snapshots can change due to the way mtime updates work,
but the contents of a snapshot should not change.  So the issue comes down
to the directory rename operation you did, which definitely should NOT show
up in a prior snapshot.  Nor should any other additions or deletions.  I
was not able to reproduce the rename / add / delete issues you reported.

It might be due to how you are accessing the snapshot.  You are providing a
path, such as "/var/hammer/home/andrea/snap-20170406-0957/bin/ ...", but
what is 'snap-20170406-0957' ?  Is it a softlink to something?  Is it a
mount?

Try CD'ing into the snapshot using the TID snapshot format.  That is, do a
'hammer snapls' to list available snapshots, then CD into one of them using
cd .@@0x<fullsnapshottid>.  Then go from there.

-Matt

On Fri, Apr 7, 2017 at 4:21 AM, Andrea <tech_lists at mail.com> wrote:

> Hi, with help form this list I've set-up my main main workstation  and
> almost ported all my work to DragonFly BSD (thanks!)
>
> Now I'm moving all my data and but I'm left with one problem I'm not able
> to sort out: some of the changes to files are propagated in older
> snapshots! It's obviously impossible so or I've done something horribly
> wrong during disk set-up or I don't understand how snapshots works.
>
> The "short" version:
>
> 1) /home/andrea/ is my home directory in a master PFS
> 2) /home/attic/ is another directory in another master PFS
> 3) Both PFSs have a snapshot done yesterday.
> 4) If I add or remove files sometimes changes are not visible in
> yesterday's snapshots, but sometimes they are.
>
> As an example, today I've added (added, not modified) this file:
> % ls -l /home/attic/disk_stats.txt
> -rw-r--r--  1 andrea  wheel  167 Apr  7 11:38 /home/attic/disk_stats.txt
>
> And I found it in yesterday's snapshot:
> % ls -l /var/hammer/home/attic/snap-20170406-0957/disk_stats.txt
> -rw-r--r--  1 andrea  wheel  167 Apr  7 11:37
> /var/hammer/home/attic/snap-20170406-0957/disk_stats.txt
>
> File date in the snapshot is 1 minute earlier than original but the file
> shouldn't be there at all.
>
> 5) Another example: today I moved a whole directory from /home/attic/ to
> /home/andrea/ and:
> - It disappeared from /home/attic/ yesterday's snapshot
> - It appeared in /home/andrea/ yesterday's snapshot
> - Files in /home/andrea/ kept the last modify dates while files in the
> snapshot have the date of the moment I moved the directory
>
> 6) I'm 100% sure I didn't move file directly inside the snapshot directory
>
>
> Some details:
>
> 1) OS version is DragonFly v4.8.0-RELEASE #4
> 2) Both directories /home/andrea/ and /home/attic/ are mirrored on a
> second disk.
> 3) This is the output of snapls and pfs-status for /home/andrea/:
>
> # hammer snapls /home/andrea/
> Snapshots on /home/andrea/      PFS#1
> Transaction ID          Timestamp               Note
> 0x0000000000000000      2017-04-06 09:57:34 CEST        -
>
> # hammer pfs-status /home/andrea/
> /home/andrea/   PFS#1 {
>     sync-beg-tid=0x0000000000000001
>     sync-end-tid=0x00000001183f03c0
>     shared-uuid=f030302c-1895-11e7-b1dd-714d7b6e28cc
>     unique-uuid=f0303031-1895-11e7-b1dd-714d7b6e28cc
>     label=""
>     prune-min=00:00:00
>     operating as a MASTER
>     snapshots directory defaults to /var/hammer/<pfs>
> }
>
> 4) Here I find my snapshot for /home/andrea/:
>
> # ls -l /var/hammer/home/andrea/snap-20170406-0957
> lrwxr-xr-x  1 root  wheel  33 Apr  6 09:57 /var/hammer/home/andrea/snap-20170406-0957
> -> /home/andrea/@@0x0000000000000000
>
> 5) The output of snapls and pfs-status for /home/attic/:
>
> % hammer snapls /home/attic/
> Snapshots on /home/attic/       PFS#2
> Transaction ID          Timestamp               Note
> 0x0000000000000000      2017-04-06 09:57:34 CEST        -
>
> % hammer pfs-status /home/attic/
> /home/attic/    PFS#2 {
>     sync-beg-tid=0x0000000000000001
>     sync-end-tid=0x000000011840a4b0
>     shared-uuid=7bb3b3bc-18ab-11e7-9d0e-714d7b6e28cc
>     unique-uuid=7bb3b3e1-18ab-11e7-9d0e-714d7b6e28cc
>     label=""
>     prune-min=00:00:00
>     operating as a MASTER
>     snapshots directory defaults to /var/hammer/<pfs>
> }
>
> 6) Here I find my snapshot for /home/attic:
>
> % ls -l /var/hammer/home/attic/snap-20170406-0957
> lrwxr-xr-x  1 root  wheel  32 Apr  6 09:57 /var/hammer/home/attic/snap-20170406-0957
> -> /home/attic/@@0x0000000000000000
>
> 7) I try to reproduce the problem but everything seems ok:
>
> I delete a file in my home directory and I still find it in the snapshot:
>
> $ rm /home/andrea/0
> $ ls /home/andrea/0 /var/hammer/home/andrea/snap-20170406-0957/0
> ls: /home/andrea/0: No such file or directory
> /var/hammer/home/andrea/snap-20170406-0957/0
>
> Now I add a file in my home directory and I don't find it in yesterday's
> snapshot:
>
> $ touch xxx
> $ ls -1 /home/andrea/xxx  /var/hammer/home/andrea/snap-20170406-0957/xxx
> ls: /var/hammer/home/andrea/snap-20170406-0957/xxx: No such file or
> directory
> /home/andrea/xxx
>
> 8) But, I moved a directory in my home directory *today* and I find it in
> *yesterday's* snapshot:
>
> % ls -l /home/andrea/bin/ | grep launcher
> -rwxr-xr-x  1 andrea  wheel        57 Jun 11  2013 ll.urxvt_launcher
>
> % ls -l /var/hammer/home/andrea/snap-20170406-0957/bin/ | grep launcher
> -rwxr-xr-x  1 andrea  wheel        57 Apr  7 11:42 ll.urxvt_launcher
>
> In other words: today I added the whole /bin directory inside my home and
> I find it in yesterday's snapshot. Files in my home directory have the
> original dates (2013 in this case) while version in the snapshot have the
> date of the moment I added the files. As you can see from the output above
> there's a file dated 2017-04-07 inside the snapshot dated 2017-04-06 which
> should be impossible
>
> 9) In the source directory the directory disappeared from yesterday's
> snapshots.
>
> 10) I didn't mess with the snapshot directories directly (I double checked
> my command history to be sure).
>
>
> I'm completely lost here, any suggestion about what I'm doing wrong or
> what I can do to diagnose further?
>
>
> Regards,
> Andrea
>
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