Thank you Manas, for your response.
I think I am getting your point but still I have some confusion, if you
can discuss more in detail it will certainly help me to understand this
thread. First let me tell you what I have understand. From your write
up, it is clear that writing over a CD-R is a write-once technology.
When files are written to a CD-R disk they can't be modified and the
disk can't be erased. The ISO9660 file system is first created on the
hard disc and then it is transfered to the CD-R media, right? No problem
up to this. Still I think my question is not answered..............my
question is, as the OS itsef determines the Recorder Drive as Read Only
device, how the device is getting the write permission from the OS to
start a write process. Is linux gives permission to start a write
process over a Read Only device, violating the file permission rule?
Regards
Anindya
Manas Laha wrote:
Linux Lover wrote:
From /etc/fstab it is transperant that a CD Writer is a device, which
is mounted at a certain mount point, which can access iso9660 file
system blah blah blah blah.....
There is also an option for the writer which is `ro'. If the device
enjoyes the read only status, how do we able to write on discs?
A typical entry for the device is as follows :
/dev/cdrom /mnt/cdrom iso9660 noauto,owner,ro 0 0
From the above it is clear that the device do not have a write
permission. Still it writes, how?
Regards
Anindya Banerjee
The filesystem on a random access medium has to be mounted only if
access to it is desired through the usual commands: ls, cp, mv,
read(), write() etc.
With magnetic media the usual practice is to create a filesystem by
the process called formatting and then write/read files using commands
like those above.
Due to its nature, a CD-R must be written to all at once, which means
we cannot do this 2-step process with CD-Rs (although this is changing
with CD-RWs). Instead, the iso9660 filesystem is created as a file on
a different medium (a hard disk, usually) and then this file is
written to the CD in _raw_ mode. The CD does not have to be mounted
for raw mode access. (Indeed, it should not be mounted immediately
before being written on.)
Does this answer your question?
- Manas Laha
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