Red Hat Bugzilla – Bug 65685
dd can fail to open autoloaded block device driver
Last modified: 2008-08-01 12:22:52 EDT
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Description of problem:
Running "dd if=<dev>" as user, when <dev>'s driver modules aren't loaded, is
supposed to autoload those modules. RedHat 7.3 fails to do so.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
0. Assume the CDROM is /dev/hdc.
1. As root, /sbin/rmmod the ide-cd and cdrom modules.
2. As user, dd if=/dev/hdc bs=4k count=1 of=/dev/null
Actual Results: dd's open() of /dec/hdc in step 2 failed, and modprobe failed
to insmod the ide-cd and cdrom modules.
Expected Results: The ide-cd and cdrom modules should have autoloaded, and step
2's dd command should have succeeded.
There are several other access methods that _do_ correctly
trigger the autoload:
3a. perform step 2 as root
3b. (as user) tar tvf /dev/hdc -- tar won't find an archive,
but the modules load correctly
3c. dd bs=4k count=1 of=/dev/null < /dev/hdc
regular open() and fopen() do work, just not in dd :-(
This problem is new in RedHat 7.3. It causes problems for those
of us that use custom kernels with modular floppy driver, and
build test kernels with "make bzdisk" as regular users.
Vanilla PC hardware. Vanilla RH7.3 install. RH7.2 worked.
Looks like either a config problem (are the right aliases in /etc/modules.conf?)
or a kmod bug
Thanks for the bug report. However, Red Hat no longer maintains this version of
the product. Please upgrade to the latest version and open a new bug if the problem
The Fedora Legacy project (http://fedoralegacy.org/) maintains some older releases,
and if you believe this bug is interesting to them, please report the problem in
the bug tracker at: http://bugzilla.fedora.us/