Module Copy-Does not handle sparse files properly

[Eric Wedaa]

I just found out that Ansible does not handle Sparse Files (A file with true empty space inside it) properly with the copy module.  I don't think this is a bug, but somebody should mention this in the documentation.

http://en.wikipedia.org/wiki/Sparse_file

Code to make a sparse file

#!/usr/bin/perl
## Code Blatantly stolen from Elizabeth Zwicky
#
open (HOLEYFILE, ">filewithbighole") ||
    warn "Can't create filewithbighole\n";

    select (HOLEYFILE);
    $| = 1;
    select (STDOUT);

    seek (HOLEYFILE, 1024* 1024 * 1024, 0);
    print HOLEYFILE "After the hole\n";

    ($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,$atime,$mtime,$ctime,$blksize,$blocks) = stat HOLEYFILE;

    if ($blocks * $blksize == $size) {
        warn "My holey file had no holes!\n";
    }

    close HOLEYFILE;


Ansible command

 

ansible AIX-7.1 -m copy -a "src=/home/ME/filewithbighole dest=/tmp/filewithbighole"

It fails as running out of disk space.  It's not a big deal as there are workarounds, like tar-ing up the file with the -S option to efficiently handle Sparse files.


[ME@ansible ~]$ ls -l filewithbighole
-rw-r--r--. 1 urew users 1073741839 Oct  5 18:44 filewithbighole

[ME@ansible ~]$ du -k filewithbighole
4	filewithbighole

[ME@ansible ~]$ !tar
tar -Scf filewithbighole.tar ./filewithbighole 

[ME@ansible ~]$ ls -lt filewithbighole.tar
-rw-r--r--. 1 urew users 10240 Oct  5 18:48 filewithbighole.tar

[ME@ansible ~]$ du -k filewithbighole.tar
12	filewithbighole.tar


>>>>Ericw

[Michael DeHaan]

Yeah I don't think we need to add specific sparse file handling to Ansible.

Ansible basically does a scp/sftp, so if those tools understand sparse files, it may be a matter of passing a flag or something, and we'd be open to patches for something like that I guess, if it were automatically detectable or reasonably safe to pass.

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[Eric Wedaa]

I just think a note needs to be made in the documentation about it, and call it good.

>>Ericw