fdisk

fdisk

[Bruce Dubbs]

I have a question about (or a enhancement request) running fdisk.  When 
asking to list known partition types, I get about 70 lines of output. 
Generally that would not be a problem, but I was running in a Debian 
install/rescue iso that uses busybox in a 25 line terminal.  I do not 
have a way to scroll up and thus cannot see the first 40 or so partition 
types.

Is there a way to use a pager for this?  In this situation 'more' is 
available but 'less' is not.  Otherwise I think an automatic pause every 
20 lines or so would be appropriate to build into the partition type 
listing.

   -- Bruce Dubbs

Re: fdisk

[Bernhard Voelker]

On 08/31/2015 04:04 AM, Bruce Dubbs wrote:
> I have a question about (or a enhancement request) running fdisk.  When 
> asking to list known partition types, I get about 70 lines of output. 
> Generally that would not be a problem, but I was running in a Debian 
> install/rescue iso that uses busybox in a 25 line terminal.  I do not 
> have a way to scroll up and thus cannot see the first 40 or so partition 
> types.
> 
> Is there a way to use a pager for this?  In this situation 'more' is 
> available but 'less' is not.  Otherwise I think an automatic pause every 
> 20 lines or so would be appropriate to build into the partition type 
> listing.

hmm, I'm getting 27 lines (at a maximum line length of 79 characters) as
output of the 'l' command  here - even if I resize the xterm to 20x80
characters.
OTOH, the main help output via the 'm' command uses 38 lines.  Shouldn't
you also have issues with that one in your environment?

Have a nice day,
Berny

Re: fdisk

[Bruce Dubbs]

Bernhard Voelker wrote:
> On 08/31/2015 04:04 AM, Bruce Dubbs wrote:
>> I have a question about (or a enhancement request) running fdisk.  When
>> asking to list known partition types, I get about 70 lines of output.
>> Generally that would not be a problem, but I was running in a Debian
>> install/rescue iso that uses busybox in a 25 line terminal.  I do not
>> have a way to scroll up and thus cannot see the first 40 or so partition
>> types.
>>
>> Is there a way to use a pager for this?  In this situation 'more' is
>> available but 'less' is not.  Otherwise I think an automatic pause every
>> 20 lines or so would be appropriate to build into the partition type
>> listing.
>
> hmm, I'm getting 27 lines (at a maximum line length of 79 characters) as
> output of the 'l' command  here - even if I resize the xterm to 20x80
> characters.
> OTOH, the main help output via the 'm' command uses 38 lines.  Shouldn't
> you also have issues with that one in your environment?

In a konsole terminal resized to

# echo $LINES
25
# fdisk --version
fdisk from util-linux 2.26.2

Yes, the main menu scrolls off the top do the topmost line is:

n   add a new partition

but that is not a big problem in konsole because I can scroll back the 
buffer.  The l command lists the partition types and the topmost line of 
the screen is entry number 44.

If it's meaningful, for konsole, I do not use a LANG or any LC_* 
variables and the TERM variable is xterm.

The difficult problem is in busybox where there is no scroll back 
capability.

The problem should be relatively easy to reproduce.  Get a copy of 
debian-8.1.0-amd64-DVD-1.iso and boot it either to HW or in a virtual 
system (I'm using qemu).  Follow the prompts and drop to a terminal and 
then run fdisk.

   -- Bruce


   -- Bruce

Re: fdisk

[Isaac Dunham]

On Mon, Aug 31, 2015 at 11:20:24AM -0500, Bruce Dubbs wrote:
> Bernhard Voelker wrote:
> >On 08/31/2015 04:04 AM, Bruce Dubbs wrote:
> >>I have a question about (or a enhancement request) running fdisk.  When
> >>asking to list known partition types, I get about 70 lines of output.
> >>Generally that would not be a problem, but I was running in a Debian
> >>install/rescue iso that uses busybox in a 25 line terminal.  I do not
> >>have a way to scroll up and thus cannot see the first 40 or so partition
> >>types.
> >>
> >>Is there a way to use a pager for this?  In this situation 'more' is
> >>available but 'less' is not.  Otherwise I think an automatic pause every
> >>20 lines or so would be appropriate to build into the partition type
> >>listing.
> >
> >hmm, I'm getting 27 lines (at a maximum line length of 79 characters) as
> >output of the 'l' command  here - even if I resize the xterm to 20x80
> >characters.
> >OTOH, the main help output via the 'm' command uses 38 lines.  Shouldn't
> >you also have issues with that one in your environment?
> 
> In a konsole terminal resized to
> 
> # echo $LINES
> 25
> # fdisk --version
> fdisk from util-linux 2.26.2
> 
> Yes, the main menu scrolls off the top do the topmost line is:
> 
> n   add a new partition
> 
> but that is not a big problem in konsole because I can scroll back the
> buffer.  The l command lists the partition types and the topmost line of the
> screen is entry number 44.
> 
> The difficult problem is in busybox where there is no scroll back
> capability.

If you do not switch VTs, the Linux kernel has a limited "scroll back"
capability:
use <Shift>+<PgUp> or <Shift>+<PgDn>.

There are serious enough limitations to this that it's not really viable
except as a workaround:
-only things that have been on-screen after you last switched to the
current VT will be visible
-switch VTs, and you lose history

But it may be useful to you.

HTH,
Isaac Dunham

Re: fdisk

[Karel Zak]

On Sun, Aug 30, 2015 at 09:04:48PM -0500, Bruce Dubbs wrote:
> I have a question about (or a enhancement request) running fdisk.  When
> asking to list known partition types, I get about 70 lines of output.
> Generally that would not be a problem, but I was running in a Debian
> install/rescue iso that uses busybox in a 25 line terminal.  I do not have a
> way to scroll up and thus cannot see the first 40 or so partition types.
> 
> Is there a way to use a pager for this?  In this situation 'more' is
> available but 'less' is not.  Otherwise I think an automatic pause every 20
> lines or so would be appropriate to build into the partition type listing.

We have lib/pager.c and setup_pager(), but it assumes that the pager
is running all time and maintain stdout until parent process
terminate.

Maybe we can implement something like

 pid = setup_temporary_pager();
    <list partition types>
 close_pager(pid);

as I don't think we want to use pager all time for fdisk. 

Volunteers?:-)

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: fdisk

[Isaac Dunham]

On Mon, Aug 31, 2015 at 12:06:48PM +0200, Karel Zak wrote:
> On Sun, Aug 30, 2015 at 09:04:48PM -0500, Bruce Dubbs wrote:
> > I have a question about (or a enhancement request) running fdisk.  When
> > asking to list known partition types, I get about 70 lines of output.
> > Generally that would not be a problem, but I was running in a Debian
> > install/rescue iso that uses busybox in a 25 line terminal.  I do not have a
> > way to scroll up and thus cannot see the first 40 or so partition types.
> > 
> > Is there a way to use a pager for this?  In this situation 'more' is
> > available but 'less' is not.  Otherwise I think an automatic pause every 20
> > lines or so would be appropriate to build into the partition type listing.
> 
> We have lib/pager.c and setup_pager(), but it assumes that the pager
> is running all time and maintain stdout until parent process
> terminate.
> 
> Maybe we can implement something like
> 
>  pid = setup_temporary_pager();
>     <list partition types>
>  close_pager(pid);
> 
> as I don't think we want to use pager all time for fdisk. 
> 
> Volunteers?:-)
> 
>     Karel

I'm tempted to volunteer, but I'd like to run something by you first.

I presume that setup_temporary_pager() needs to spawn a pager, with
the pager inheriting stdout/stderr and stdout temporarily redirected
to the pipe, and then close_pager() needs to close the pipe and swap
the old stdout/stderr back in, then wait for pid to exit.

Thus, I'm thinking that the following prototypes would be better:

/* create a pipe, spawn a temporary pager,
 * dup()s fd 1 and possibly fd 2 before redirecting to the pipe
 * if an fd is not dup()'d, set the corresponding duplicate to -1
 */
pid_t setup_temporary_pager(int *dupout, int *duperr);

/* close the pipe, dup2() the saved fds back over fds 1/2,
 * close the duplicates, and wait for the temporary pager to exit
 * if either fd is -1, skip it.
 */
void close_pager(pid, int dupout, int duperr);


setup_temporary_pager will return -1 if it does not spawn the pager
(whether by failure or by PAGER=cat), or if there are problems during
the redirection dance.
It will refuse to spawn a pager if (!isatty(STDOUT_FILENO)).

Does this sound sensible?

Thanks,
Isaac Dunham

Re: fdisk

[Karel Zak]

On Tue, Sep 01, 2015 at 07:07:34PM -0700, Isaac Dunham wrote:
> Thus, I'm thinking that the following prototypes would be better:
> 
> /* create a pipe, spawn a temporary pager,
>  * dup()s fd 1 and possibly fd 2 before redirecting to the pipe
>  * if an fd is not dup()'d, set the corresponding duplicate to -1
>  */
> pid_t setup_temporary_pager(int *dupout, int *duperr);
> 
> /* close the pipe, dup2() the saved fds back over fds 1/2,
>  * close the duplicates, and wait for the temporary pager to exit
>  * if either fd is -1, skip it.
>  */
> void close_pager(pid, int dupout, int duperr);
> 
> 
> setup_temporary_pager will return -1 if it does not spawn the pager
> (whether by failure or by PAGER=cat), or if there are problems during
> the redirection dance.
> It will refuse to spawn a pager if (!isatty(STDOUT_FILENO)).

Yes, on non-tty stdout the both functions have to do nothing.

> Does this sound sensible?

Yes, go ahead.


    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

fdisk

[Bruce Dubbs]

In fdisk, printing a partition table gives the headers:

Device Boot      Start         End      Blocks   Id  System

What's a block?  It does not seem to be defined anywhere.  Perhaps an 
update to the man page would be appropriate.  A line in the explanation 
above the partition listing would be even better.

On my system, a block appears to be 2-512 byte sectors, but is it always so?

   -- Bruce

Re: fdisk

[Karel Zak]

On Fri, Jun 24, 2011 at 01:25:39PM -0500, Bruce Dubbs wrote:
> On my system, a block appears to be 2-512 byte sectors, but is it
> always so?

 Yes. It's stupid legacy (the same thing you can found in
 /proc/partitions).

 I hope that one day we will have better and nicer fdisk with 
 human readable sizes ;-)

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com

Re: fdisk

[Mike Frysinger]

[-- Attachment #1: Type: Text/Plain, Size: 440 bytes --]

On Monday, June 27, 2011 10:21:19 Karel Zak wrote:
> On Fri, Jun 24, 2011 at 01:25:39PM -0500, Bruce Dubbs wrote:
> > On my system, a block appears to be 2-512 byte sectors, but is it
> > always so?
> 
>  Yes. It's stupid legacy (the same thing you can found in
>  /proc/partitions).
> 
>  I hope that one day we will have better and nicer fdisk with
>  human readable sizes ;-)

and merge duplicated code with cfdisk ;)
-mike

[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 836 bytes --]

fdisk

[azie]

I'm using Dell Dimension PIV 2.0 with 40GB harddisk. When I try to use fdisk 
to repartition my harddisk, I got this error.

[begin]

# fdisk /dev/hda

Command (m for help): p

Disk /dev/hda: 255 heads, 63 sectors, 2491 cylinders
Units = cylinders of 16065 * 512 bytes


8 partitions:
#       start       end      size     fstype   [fsize bsize   cpg]
  a:        1         7*        6*    4.2BSD     1024  8192    16
  b:        7*       40*       32*      swap
  c:        1      2492*     2491*    unused        0     0
  e:       40*       42*        2*    4.2BSD     1024  8192    16
  f:       42*     2492*     2449*    4.2BSD     1024  8192    16

Command (m for help): n
Segmentation fault

#

[end]

any idea why this happens and how to partition it using fdisk?

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Re: fdisk

[Ray Olszewski]

A segfault occurs when a program attempts to access memory that the kernel 
has not allocated to it. In practice, a segfault error message usually 
means one of two things:

         1. A bug in the application being run. A common one is trying to 
read past the end of an array; C does not have a built-in check for this, 
and programmers too often forget to do range checking.

         2. A hardware problem, typically flaky RAM (which can trash an 
address pointer).

Without more information about your setup, I can't really tell you more 
about the error.

On the hardware side, how much RAM does the system have? Does the system 
segfault on other occasions?

On the software side, what Linux distribution and version? What version of 
fdisk (your -p printout is very different from mine, and I'm quite curious 
as to why it says it has 8 partitions but only lists 5)? Why is your Linux 
system using only BSD partitions ... or are they partitions from a prior OS 
that you are trying to replace? And where are you running fdisk from (the 
installer floppy or CD of your Linux distro, or what)?

Also, I may be reading it wrong (as I said, my fdisk has a different 
format), but it appears that even if fdisk were working, you couldn't add a 
new partition to that disk, since the 4 usable partitions (that is, 
excluding the extended partition shown in your list as C: and, presumably 
incorrectly, labeled "unused") already use all 2491 cylinders, leaving no 
space for new partitions. Assuming the BSD partitions are from a prior 
installation of an OS you are replacing, I'd suggest you first try deleting 
one or more of them to provide some room for Linux partitions.

At 11:36 AM 7/17/02 +0800, azie wrote:
>I'm using Dell Dimension PIV 2.0 with 40GB harddisk. When I try to use fdisk
>to repartition my harddisk, I got this error.
>
>[begin]
>
># fdisk /dev/hda
>
>Command (m for help): p
>
>Disk /dev/hda: 255 heads, 63 sectors, 2491 cylinders
>Units = cylinders of 16065 * 512 bytes
>
>
>8 partitions:
>#       start       end      size     fstype   [fsize bsize   cpg]
>   a:        1         7*        6*    4.2BSD     1024  8192    16
>   b:        7*       40*       32*      swap
>   c:        1      2492*     2491*    unused        0     0
>   e:       40*       42*        2*    4.2BSD     1024  8192    16
>   f:       42*     2492*     2449*    4.2BSD     1024  8192    16
>
>Command (m for help): n
>Segmentation fault
>
>#
>
>[end]
>
>any idea why this happens and how to partition it using fdisk?


--
-----------------------------------------------"Never tell me the 
odds!"--------------
Ray Olszewski					     -- Han Solo
Palo Alto, California, USA				ray@comarre.com
-------------------------------------------------------------------------------------------

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Re: fdisk

[Elias Athanasopoulos]

On Wed, Jul 17, 2002 at 11:36:14AM +0800, azie wrote:
> 8 partitions:
> #       start       end      size     fstype   [fsize bsize   cpg]
>   a:        1         7*        6*    4.2BSD     1024  8192    16
>   b:        7*       40*       32*      swap
>   c:        1      2492*     2491*    unused        0     0
>   e:       40*       42*        2*    4.2BSD     1024  8192    16
>   f:       42*     2492*     2449*    4.2BSD     1024  8192    16
> 
> Command (m for help): n
> Segmentation fault

If you had installed *BSD before in this disk, it is possible that fdisk
can understand slices and partitions and thus it segfaults.

It is an fdisk bug for sure. Whatever the case is with your disk, it must
not segfault.

Elias

-- 
http://gnewtellium.sourceforge.net			MP3 is not a crime.	
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Re: fdisk

[Bryan Whitehead]

Is libsafe being pre-loaded in /etc/ld.so.preload ?

I had problems with fsck, fdisk, and mkfs.ext2 when libsafe was being 
preloaded.

If the partition table is in some weird format, and you don't care about 
the data on the disk. You could just wipe the disk clean before you 
fdisk it. 'dd if=/dev/zero of=/dev/hda'

azie wrote:
> I'm using Dell Dimension PIV 2.0 with 40GB harddisk. When I try to use fdisk 
> to repartition my harddisk, I got this error.
> 
> [begin]
> 
> # fdisk /dev/hda
> 
> Command (m for help): p
> 
> Disk /dev/hda: 255 heads, 63 sectors, 2491 cylinders
> Units = cylinders of 16065 * 512 bytes
> 
> 
> 8 partitions:
> #       start       end      size     fstype   [fsize bsize   cpg]
>   a:        1         7*        6*    4.2BSD     1024  8192    16
>   b:        7*       40*       32*      swap
>   c:        1      2492*     2491*    unused        0     0
>   e:       40*       42*        2*    4.2BSD     1024  8192    16
>   f:       42*     2492*     2449*    4.2BSD     1024  8192    16
> 
> Command (m for help): n
> Segmentation fault
> 
> #
> 
> [end]
> 
> any idea why this happens and how to partition it using fdisk?
> 
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
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-- 
Bryan Whitehead
SysAdmin - JPL - Interferometry Systems and Technology
Phone: 818 354 2903
driver@jpl.nasa.gov

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Re: fdisk

[azie]

i don't have libsafe in /etc/ld.so.conf . The problem only occurs in /dev/hda. 
My /dev/hdb shows normal fdisk printout & can performs all fdisk commands :

Disk /dev/hdb: 255 heads, 63 sectors, 4863 cylinders
Units = cylinders of 16065 * 512 bytes

   Device Boot    Start       End    Blocks   Id  System
/dev/hdb1             1       392   3148708+   b  Win95 FAT32

The hda harddisk is the original harddisk that comes with Dell PC and 
previously preloaded with Windows XP. I wipe out everything during RedHat 7.3 
installation. The only way for me to partition & format the hda is during RH 
installation. Just wondering what exactly wrong with the harddisk. :)

On Thursday 18 July 2002 02:25 am, Bryan Whitehead wrote:
> Is libsafe being pre-loaded in /etc/ld.so.preload ?
>
> I had problems with fsck, fdisk, and mkfs.ext2 when libsafe was being
> preloaded.
>
> If the partition table is in some weird format, and you don't care about
> the data on the disk. You could just wipe the disk clean before you
> fdisk it. 'dd if=/dev/zero of=/dev/hda'
>
> azie wrote:
> > I'm using Dell Dimension PIV 2.0 with 40GB harddisk. When I try to use
> > fdisk to repartition my harddisk, I got this error.
> >
> > [begin]
> >
> > # fdisk /dev/hda
> >
> > Command (m for help): p
> >
> > Disk /dev/hda: 255 heads, 63 sectors, 2491 cylinders
> > Units = cylinders of 16065 * 512 bytes
> >
> >
> > 8 partitions:
> > #       start       end      size     fstype   [fsize bsize   cpg]
> >   a:        1         7*        6*    4.2BSD     1024  8192    16
> >   b:        7*       40*       32*      swap
> >   c:        1      2492*     2491*    unused        0     0
> >   e:       40*       42*        2*    4.2BSD     1024  8192    16
> >   f:       42*     2492*     2449*    4.2BSD     1024  8192    16
> >
> > Command (m for help): n
> > Segmentation fault
> >
> > #
> >
> > [end]
> >
> > any idea why this happens and how to partition it using fdisk?
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-newbie"
> > in the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.linux-learn.org/faqs

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