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As far I know, /dev/cdrom usually provides a read-only device. However, some sources suggest to add ro in the /etc/fstab and others not.

Is there a difference between

/dev/cdrom /mnt/cdrom auto noauto,user 0 0


/dev/cdrom /mnt/cdrom auto noauto,user,ro 0 0

or will mount add always ro? And if so, from where does it exactly know that the device is read- only?

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up vote 2 down vote accepted

The only difference is that you get a message e.g.

mount: block device /dev/sr1 is write-protected, mounting read-only

'ro' avoids the message.

The device driver will tell the OS that the device is write protected.

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