Re: parted is ALMOST suitable

From	Reco <recoverym4n@gmail.com>
Newsgroups	linux.debian.user
Subject	Re: parted is ALMOST suitable
Date	2016-11-07 18:00 +0100
Message-ID	<sAVr3-5FZ-9@gated-at.bofh.it> (permalink)
References	(2 earlier) <sAS9Q-3GK-29@gated-at.bofh.it> <sASWd-4ht-13@gated-at.bofh.it> <sAT5T-4ky-9@gated-at.bofh.it> <sATfA-4nB-21@gated-at.bofh.it> <sATIB-4Mo-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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	Hi.

On Mon, Nov 07, 2016 at 04:05:17PM +0100, tomas@tuxteam.de wrote:
> On Mon, Nov 07, 2016 at 09:35:32AM -0500, Greg Wooledge wrote:
> > I started writing that in my previous message, but then I actually
> > tested it on my own system.  Good thing I did, because I got the
> > same result as Richard: being in group disk, which has read/write
> > access on /dev/sda*, does NOT give you output in the FSTYPE and other
> > fields of lsblk -f.  It certainly surprised me.
> 
> Indeed. I suspect lsblk is checking the user ID itself instead of
> letting the OS do its thing. For whatever reasons I can't fathom.

According to the source (util-linux-2.25.2), '-f' flag should add these
to the output:

add_column(columns, ncolumns++, COL_NAME);
add_column(columns, ncolumns++, COL_FSTYPE);
add_column(columns, ncolumns++, COL_LABEL);
add_column(columns, ncolumns++, COL_UUID);
add_column(columns, ncolumns++, COL_TARGET);


To determine COL_FSTYPE, probe_device function is used.
The definition of this function contains this little gem (getuid call):

static void probe_device(struct blkdev_cxt *cxt)
{
...

    /* try udev DB */
    if (get_udev_properties(cxt) == 0)
        return;             /* success */

    cxt->probed = 1;

    /* try libblkid (fallback) */
    if (getuid() != 0)
        return;             /* no permissions to read from the device */

    pr = blkid_new_probe_from_filename(cxt->filename);
    if (!pr)
        return;

So whoever wrote this was either lazy or too smart or both, as
blkid_new_probe_from_filename does this:

blkid_probe blkid_new_probe_from_filename(const char *filename)
{
...

    fd = open(filename, O_RDONLY|O_CLOEXEC);
    if (fd < 0)
        return NULL;

I.e. insufficient device permissions will return NULL anyway, so there's
little point of checking whenever the calling user is root or not.

Reco

Thread

parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 13:20 +0100
  Re: parted is ALMOST suitable Felipe Salvador <felipe.salvador@gmail.com> - 2016-11-07 13:30 +0100
    Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 13:40 +0100
      Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 14:00 +0100
        Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 14:20 +0100
          Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 15:00 +0100
            Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 15:50 +0100
              Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 16:10 +0100
              Re: parted is ALMOST suitable Lisi Reisz <lisi.reisz@gmail.com> - 2016-11-07 17:30 +0100
      Re: parted is ALMOST suitable Felipe Salvador <felipe.salvador@gmail.com> - 2016-11-07 15:30 +0100
        Re: parted is ALMOST suitable Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-11-07 16:20 +0100
          Re: parted is ALMOST suitable Aldo Maggi <aldomaggi@katamail.com> - 2016-11-07 18:20 +0100
          Re: parted is ALMOST suitable Felipe Salvador <felipe.salvador@gmail.com> - 2016-11-07 19:00 +0100
          Re: parted is ALMOST suitable Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-11-08 19:10 +0100
            Re: parted is ALMOST suitable Glenn English <ghe2001@gmail.com> - 2016-11-08 19:40 +0100
              Re: parted is ALMOST suitable Stefan Monnier <monnier@iro.umontreal.ca> - 2016-11-08 21:10 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-08 21:50 +0100
                Re: parted is ALMOST suitable Stefan Monnier <monnier@iro.umontreal.ca> - 2016-11-09 00:20 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 18:40 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 21:40 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 21:50 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 22:20 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 09:50 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 11:20 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 11:30 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 11:50 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 12:10 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 17:10 +0100
                Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-09 15:20 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 20:50 +0100
                Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-09 21:40 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 21:10 +0100
                Re: parted is ALMOST suitable Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2016-11-10 01:20 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-10 10:10 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-09 19:30 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 21:40 +0100
                Re: parted is ALMOST suitable Stefan Monnier <monnier@iro.umontreal.ca> - 2016-11-08 22:10 +0100
                Re: parted is ALMOST suitable Lisi Reisz <lisi.reisz@gmail.com> - 2016-11-09 16:00 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-09 09:40 +0100
        Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 16:30 +0100
          Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-07 17:10 +0100
            Re: parted is ALMOST suitable Felipe Salvador <felipe.salvador@gmail.com> - 2016-11-07 18:50 +0100
              Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-07 20:20 +0100
                Re: parted is ALMOST suitable Lisi Reisz <lisi.reisz@gmail.com> - 2016-11-08 00:50 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-08 01:40 +0100
                Re: parted is ALMOST suitable Michael Lange <klappnase@freenet.de> - 2016-11-08 03:50 +0100
                Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-08 12:00 +0100
                Correction - Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-08 12:20 +0100
                Re: Correction - Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-08 20:30 +0100
                Re: parted is ALMOST suitable David Wright <deblis@lionunicorn.co.uk> - 2016-11-08 13:50 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-08 20:10 +0100
  Re: parted is ALMOST suitable Frank <zuiderduin@gmx.com> - 2016-11-07 13:30 +0100
  Re: parted is ALMOST suitable Darac Marjal <mailinglist@darac.org.uk> - 2016-11-07 13:40 +0100
  Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 13:50 +0100
    Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 14:30 +0100
      Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 15:10 +0100
      Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 15:20 +0100
        Re: parted is ALMOST suitable Greg Wooledge <wooledg@eeg.ccf.org> - 2016-11-07 15:30 +0100
          Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 15:40 +0100
          Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-07 17:00 +0100
            Re: parted is ALMOST suitable Greg Wooledge <wooledg@eeg.ccf.org> - 2016-11-07 17:10 +0100
              Re: parted is ALMOST suitable Nicolas George <george@nsup.org> - 2016-11-07 17:20 +0100
        Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 15:30 +0100
          Re: parted is ALMOST suitable Greg Wooledge <wooledg@eeg.ccf.org> - 2016-11-07 15:40 +0100
            Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 16:10 +0100
              Re: parted is ALMOST suitable Reco <recoverym4n@gmail.com> - 2016-11-07 18:00 +0100
                Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-08 10:20 +0100
        Re: parted is ALMOST suitable Pascal Hambourg <pascal@plouf.fr.eu.org> - 2016-11-07 21:10 +0100
          Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-08 01:00 +0100
            Re: parted is ALMOST suitable Richard Owlett <rowlett@cloud85.net> - 2016-11-08 12:20 +0100
            Re: parted is ALMOST suitable Pascal Hambourg <pascal@plouf.fr.eu.org> - 2016-11-11 15:40 +0100
              Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-11 17:30 +0100
                Re: parted is ALMOST suitable Pascal Hambourg <pascal@plouf.fr.eu.org> - 2016-11-11 18:10 +0100
                Re: parted is ALMOST suitable Brian <ad44@cityscape.co.uk> - 2016-11-11 18:40 +0100
    Re: parted is ALMOST suitable David Wright <deblis@lionunicorn.co.uk> - 2016-11-07 15:10 +0100
      Re: parted is ALMOST suitable <tomas@tuxteam.de> - 2016-11-07 15:10 +0100
  Re: parted is ALMOST suitable rhkramer@gmail.com - 2016-11-07 15:00 +0100

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