I've run into an error stemming from lacking permissions when using the CDIO library to issue an eject command to my USB CD-ROM drive. I always get an error message like this:
INFO: ioctl CDROM_SEND_PACKET for command PREVENT ALLOW MEDIUM REMOVAL (0x1e) failed: Operation not permitted
The ioctl
call is part of the cdda-player
app I call as follows:
cdda-player -ev /dev/sr0
After taking a look into the sourcecode of libcdio
, I found out that this line of code makes trouble:
int i_rc = ioctl (p_env->gen.fd, CDROM_SEND_PACKET, &cgc);
When I run the code as root (using sudo
), everything works fine. Here are the permissions for my CD-ROM drive:
pi@autoradio:/import/valen/autoradio/libcdio-master $ ls -al /dev/sr0
brw-rw----+ 1 root cdrom 11, 0 Jul 5 22:42 /dev/sr0
pi@autoradio:/import/valen/autoradio/libcdio-master $ ls -al /dev/sg0
crw-rw----+ 1 root cdrom 21, 0 Jul 5 22:38 /dev/sg0
pi@autoradio:~ $ getfacl /dev/sr0
getfacl: Removing leading '/' from absolute path names
# file: dev/sr0
# owner: root
# group: cdrom
user::rw-
user:pi:rw-
group::rw-
mask::rw-
other::---
The user pi
is part of the cdrom
group. The standard eject
utility does work, though.
Now: Which permissions do I have to set for the eject operation to work as an ordinary user? Thank you.
UPDATE: Here is my kernel version:
pi@autoradio:/import/valen/autoradio/libcdio-master $ uname -a
Linux autoradio 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux
Best Answer
OK, after a hint from one of the maintainers of
libcdio
, I found out that the version I installed was out of date and contained a bug based on improper use ofO_RDWR
vs.O_RDONLY
. After the update, suddenly everything works fine. Nevertheless thank you for your hints!