Wish to enable cdrom

[KStorm]

Under System Settings>Disk and Filesystems, my CD Burner shows up as disabled. 

After entering Admin mode, I sought to enable but ended up getting an "Error 32: Mount Failure".

How do I fix this?  Thanks.

[Nirvana]

Re: Wish to enable cdrom

post your /etc/fstab (cat /etc/fstab)

[KStorm]

Re: Wish to enable cdrom

# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
/dev/hdb3 / ext3 nouser,defaults,errors=remount-ro,atime,auto,rw,dev,exec,suid 0 1
/dev/hdb2 /home ext3 nouser,defaults,atime,auto,rw,dev,exec,suid 0 2
/dev/hda1 /media/hda1 vfat defaults,utf8,umask=007,uid=0,gid=46,auto,rw,nouse r 0 1
/dev/hda2 /media/hda2 ntfs defaults,nls=utf8,umask=007,uid=0,gid=46,auto,rw,n ouser 0 1
/dev/hdb1 /media/hdb1 vfat defaults,utf8,umask=007,uid=0,gid=46,auto,rw,nouse r 0 1
/dev/hdb4 none swap sw 0 0
/dev/hdc /media/cdrom0 auto user,atime,auto,rw,dev,exec,suid 0 0

[Fenyx]

Re: Wish to enable cdrom

You don't have to enable the CD-ROM in Disks and Filesystems. It automatically mounts whenever there's a CD inside.

Your fstab entry looks fine. Have you tried actually putting a in a CD?

[kubicle]

Re: Wish to enable cdrom

Yes...you don't mount the drive, you mount the filesystem on a disk (which means there must be a disk in the drive)

Also, using the 'auto' option in fstab doesn't make much sense for removable media, since there isn't always a disk in the drive when the system boots or when you run 'mount -a'

a simpler fstab line could be:

/dev/hdc  /media/cdrom0  udf,iso9660  user,noauto 0 0

('atime' and 'rw' are defaults...exec and suid are a slight local security risk on user mountable removable media )

[Fenyx]

Re: Wish to enable cdrom

Also, using the 'auto' option in fstab doesn't make much sense for removable media, since there isn't always a disk in the drive when the system boots or when you run 'mount -a'

a simpler fstab line could be:

/dev/hdc /media/cdrom0 udf,iso9660 user,noauto 0 0

('atime' and 'rw' are defaults...exec and suid are a slight local security risk on user mountable removable media)

I wonder, then, why the Kubuntu installer uses these default fstab entries...

@kubicle: do you have any link that explains these fstab options?

[kubicle]

Re: Wish to enable cdrom

[I wonder, then, why the Kubuntu installer uses these default fstab entries...

You mean the installer sets up cdrom fstab entry like that? Beats me, maybe the installer needs to run programs from the CD with root privileges (just a quick guess that might be way off...haven't had time to ponder this one )

Also there is no harm in writing the 'default options' (like 'rw') to fstab...just that they are redundant.

@kubicle: do  you have any link that explains these fstab options?

man mount

describes the mount options available for different filesystems

[Fenyx]

Re: Wish to enable cdrom

Thanks for the reference to the man pages. Again I'm taught a valuable lesson to consult it first before asking away.

But anyway, why would 'exec' be a security risk? Something like a self-extracting/executing virus or malware? What would be another option if I actually wanted to execute something on that CD, an installer, for example.

And I can't understand what suid does...
Guess I just lack the technical vocabulary.

[kubicle]

Re: Wish to enable cdrom

But anyway, why would 'exec' be a security risk? Something like a self-extracting/executing virus or malware? What would be another option if I actually wanted to execute something on that CD, an installer, for example.

And I can't understand what suid does...
Guess I just lack the technical vocabulary.

'exec' allows execution of binaries from the mounted filesystem. In itself it is not a big risk unless you have a habit of running unknown binaries from removable media (with root privileges, for maximum damage )

combined with 'suid' it can be hazardous, as it allows the 'suid bit' in file permissions on the media. Binaries with 'suid' (chmod 4XXX) are always run as the owner of the file, regardless of who executes it, which means that a binary owned by root (removable media are mounted owned by root, by default) can be run with root privileges by a regular user from the cd.

So theoretically a regular user can pop in (his own) cd which has suid executables, and run them as root in the machine. This isn't a major issue since this can be done with a LiveCD just as well, but allowing 'exec,suid' can cause 'accidental' ill effects.

Also, though 'exec' and 'suid' are 'enabled as default options'...setting 'user' or 'users' option implies 'noexec' and 'nosuid'...so if you want to enable 'exec' and 'suid' with 'user' option you have to write them after 'user' or otherwise they will be set as 'noexec' and 'nosuid' (the same is true for 'dev')


(Hmm...I hope that makes sense, I could have worded it a bit better :P)

[Fenyx]

Re: Wish to enable cdrom

I guess I understand a bit now. Thanks for the short tutorial.
But what if I really needed/wanted to execute a binary (whether it be a Linux or a Windows binary) from the cdrom? noexec would prevent that, right?
Also, what about this little quote from the man mount page?

nosuid
Do not allow set-user-identifier or set-group-identifier bits to take effect. (This seems safe, but is in fact rather unsafe if you have suidperl(1) installed.)

Anyway, it's getting really off-topic. sorry about that. I guess I'll be reviewing my fstab (or make another topic for this )

[kubicle]

Re: Wish to enable cdrom

I guess I understand a bit now. Thanks for the short tutorial.
But what if I really needed/wanted to execute a binary (whether it be a Linux or a Windows binary) from the cdrom? noexec would prevent that, right?

Like I mentioned, 'exec' alone isn't a 'big deal' if you need to execute from the media.

Also, what about this little quote from the man mount page?

nosuid
Do not allow set-user-identifier or set-group-identifier bits to take effect. (This seems safe, but is in fact rather unsafe if you have suidperl(1) installed.)

AFAIK suidperl is a bit misbehaving (known issue), it can run target scripts as suid even if the target filesystem is mounted 'nosuid'...however this doesn't mean that 'nosuid' is less secure than 'suid' if suidperl is installed.

Anyway, it's getting really off-topic.

True enough...let's continue somewhere else if we need to

[KStorm]

Re: Wish to enable cdrom

Well, the drive is doing what it needs to. I can use it; it's just that when it showed up in Disk and Filesystems as disabled I immediately thought I had to rectify the situation.