File permissions not sticking, DMA not working...

Gveto · 12-14-2002, 11:01 PM

Hello...
I have been trying to change the file permissions of my DVD drive block device file /dev/hdd after I had to remake this file with MAKEDEV... All seemed to go well, but the owner and the permissions were wrong. The owner was listed as (user) and the permissions were set to -rw------- , so I quickly changed the permissions on the file, and then the owner to root to correspond to the rest of the /dev files, but when I log out of Linux, and log back in, the permissions revert to their original state.
I don't know how important these permissions are, because I can use and mount the drive perfectly, but I cannot turn on DMA.

Here's what I tried:

Code:

[root@wyc412djh-1 root]# hdparm -d1 /dev/hdd

/dev/hdd:
 setting using_dma to 1 (on)
 HDIO_SET_DMA failed: Operation not permitted
 using_dma    =  0 (off)

Why aren't the permissions I set to /dev/hdd sticking, and why can't I turn DMA on for it?
Thanks a bunch.
Gveto

neo77777 · 12-14-2002, 11:15 PM

what does
hdparm -i /dev/hdd
report?

Gveto · 12-15-2002, 12:16 AM

Code:

[root@wyc412djh-1 root]# hdparm -i /dev/hdd

/dev/hdd:

 Model=IDE DVD-ROM 16X, FwRev=V3.10, SerialNo=
 Config={ Fixed Removeable DTR<=5Mbs DTR>10Mbs nonMagnetic }
 RawCHS=0/0/0, TrkSize=0, SectSize=0, ECCbytes=0
 BuffType=unknown, BuffSize=0kB, MaxMultSect=0
 (maybe): CurCHS=0/0/0, CurSects=0, LBA=yes, LBAsects=0
 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
 PIO modes:  pio0 pio1 pio2 pio3 pio4
 DMA modes:  sdma0 sdma1 sdma2 mdma0 mdma1 mdma2
 UDMA modes: udma0 udma1 udma2
 AdvancedPM=no

There you have it.
Gveto

Gveto · 12-15-2002, 10:25 PM

Anyone else?

docalton · 12-16-2002, 07:59 AM

Not sure about your permissions, but to enable dma on cdrom, you need to add the following line to your /etc/modules.conf file then reboot.

options ide-cd dma=1

That should enable dma. I'll see if I can find the permissions problem.

Hope this helps.

Gveto · 12-16-2002, 02:00 PM

docalton:
That did the trick alright... Thanks a lot.
About the file permissions; they still aren't being changed after a logout, but from what I've seen, this does not affect the working af the drive or computer... Any ideas?

Gveto

PS: docalton: Where in STL do you live? I live near STL on the IL side, but am up at Peoria for school.

SlickWilly · 12-16-2002, 02:11 PM

I'm pretty certain that you're not going to be able to change the DMA settings of your hard drive / cd on the fly... :P

Which is why it's a bootup option, and not something you can change at will while it's in operation. Think of it as one of those situations where windows tells you 'Thanks for clicking here... I have to reboot to execute your selection'.

Slick.

Gveto · 12-16-2002, 02:39 PM

Yup.. That's the case, the boot script worked just fine.

docalton · 12-16-2002, 03:40 PM

Actually, you can change the dma status "on the fly." And also, you do NOT even have to reboot. You could have just unloaded the module using "rmmod ide-cd" then reloaded the module using "modprobe ide-cd dma=1". This however is easier accomplished by using the options in the modules.conf. Unless of course this is a mission critical system and a reboot is out of the question. Then change the modules.conf file for future reboots.

GVETO: I am not really from St. Louis, I'm from the IL side to, however who has really heard of Alton, IL. Easier to say St. Louis, almost everbody knows where that is.

docalton · 12-16-2002, 04:35 PM

I havent tracked it down yet, but I also experience that problem. When I log in as myself, it changes the owner and permissions. It does however change them back when I log out. It may have something to do with users being able to mount the cd without having to be root.

You've peaked my curiosity. I'll have to find out now...

SlickWilly · 12-17-2002, 10:44 AM

Well, there you go.. learn something new every day.

I am, however, also curious. How is it you're able to remove the 'ide' driver while the device is in use. I mean.. wouldn't you have to unmount all the file systems before doing that?

docalton · 12-17-2002, 02:00 PM

you are not actually removing the entire ide driver. Just the ide cdrom driver. Yes, you probably would need to umount any ide cdroms that are mounted before you removed the module.

I guess that I just assumed that would be everybody's first thing they would do. been using linux for about 10 years, since kernel 1.1.59, but just happened across this board the other day. as such my assumtions are not always correct.

i should have been more clear, may apologies.

Chris