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From: "linux-os (Dick Johnson)" <>
To: "Mika Lawando" <>
Cc: <>
Subject: Re: Is there a "blackhole" /dev/null directory?
Date: Thu, 14 Feb 2008 10:06:33 -0500	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Thu, 14 Feb 2008, Mika Lawando wrote:

> Jasper Bryant-Greene schrieb:
>> On Thu, 2008-02-14 at 10:30 +0100, rzryyvzy wrote:
>>> /dev/null is often very useful, specially if programs force to save data in some file. But some programs like to creates different temporary file names, so /dev/null could no more work.
>>> What is with a "/dev/null"-directory?
>>> I mean a "blackhole pseudo directory" which eats every write to null.
>>> Here is how it could work:
>>> mount -t nulldir nulldir /dev/nulldir
>>> Now if a program does a create(2),
>>> it creates in the memory the file with its fd.
>>> Then if a program does a write(2) to the fd, it eats the writes and give out fakely it has written the number of bytes.
>>> When the program calls does a close(2) of the fd, then the complete inode is deleted in the memory.
>>> The directory should  be permanently empty except for the inodes with open file descriptors. So only inode information would be temporary saved in this "nulldir tmpfs" directory.
>>> Is there already existing a possibility to create a null directory?
>> This could be done fairly trivially with FUSE, and IMHO is a good use
>> for FUSE because since you're just throwing most data away, performance
>> is not a concern.
> Unfortunately performance is a concern because if not I would write on
> the hard disk the files, and then remove them with a cronjob.
> But from the point of view of the time of developpment, FUSE is a good
> idea, because its possible to write a filesystem quickly in Perl.
> -- 
> Best regards,
> Mika
> --

Creating a null directory wouldn't work because a directory
is just a link to find a file. The actual file gets written
using the file-descriptor, without any reference whosoever
to the path. If you have root privileges, you can use
`mknod tempfile c 1 3` to create a null file with any
name you want. Unfortunately, somebody decided that
you need root privileges to execute mknod so ordinary
users can not do this.

Dick Johnson
Penguin : Linux version on an i686 machine (5588.28 BogoMips).
My book :

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  reply	other threads:[~2008-02-14 15:06 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-14  9:30 rzryyvzy
2008-02-14  9:39 ` Jasper Bryant-Greene
2008-02-14  9:46   ` Andi Kleen
2008-02-14 15:00     ` Jan Engelhardt
2008-02-14 15:19       ` Hans-Jürgen Koch
2008-02-14 15:23         ` Jan Engelhardt
2008-02-14 15:30           ` Hans-Jürgen Koch
2008-02-15 19:25       ` Bill Davidsen
2008-02-14 12:16   ` Mika Lawando
2008-02-14 15:06     ` linux-os (Dick Johnson) [this message]
     [not found] <>
2008-02-14 17:16 ` Bodo Eggert
     [not found] ` <>
     [not found]   ` <>
     [not found]     ` <>
     [not found]       ` <>
2008-02-15  1:15         ` Bodo Eggert

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