[PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Max Nikulin]

Don't claim that /dev/sr<N> device names for SCSI CD-ROM drives are
deprecated and don't recommend /dev/scd<N> alternate names for them.

/dev/scd<N> device names for SCSI CD-ROM drives are not in use for more
than a decade, see commit [1] that was a part of udev release 174.
Earlier related rules were volatile, sometimes /dev/scd<N> were syminks
to /dev/sr<N>, sometimes vice versa.

Recognizing of root=/dev/scd<N> kernel command line argument was removed
in kernel 2.5.45 [2].

In the docs /dev/scd<N> are recommended names since 2.6.9 [3].
Mention of these names appeared much earlier in 1.3.22 [4].

[1] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?id=d132be4d58
    2011-08-12 14:05:19 +0200 Kay Sievers.
    rules: remove legacy rules for cdrom and usb printer

[2] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/init?h=v2.5.45&id=51924607bd
    2002-10-29 00:47:58 -0800 Alexander Viro.
    [PATCH] removal of root_dev_names[]

[3] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/Documentation/devices.txt?h=v2.6.9-rc4&id=a74e11ffeda
    2004-03-16 15:09:38 -0800 Andrew Morton:
    [PATCH] devices.txt: typos and removal of dead devices

[4] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/tree/Documentation/devices.txt?h=v2.6.9-rc4&id=8f0ec1f9369
    Linus Torvalds: Import 1.3.22

Signed-off-by: Max Nikulin <manikulin@gmail.com>

---

I hope, the suggested changes make kernel docs more close to reality.

During discussion of a bug in wodim (a fork of cdrecord) I was confused
that docs recommend /dev/scd<N> as SCSI CD-ROM name. The following
thread did not clarify the issue:

https://lore.kernel.org/lkml/20061105100926.GA2883@pelagius.h-e-r-e-s-y.com/
Scsi cdrom naming confusion; sr or scd? Sun, 5 Nov 2006 10:09:26 +0000

If I'm not mistaken, "sr" was always used internally in the driver
"scd" were limited to log strings. I have added SCSI subsystem to CC
to confirm that there is no objection from their side.

It seems, de-facto /dev/sr<N> names are used and I think, /dev/scd<N>
should be avoided. I may be completely wrong though.

I wouldn't mind if you discard this patch and to commit another one
with better wording instead.
---
 Documentation/admin-guide/devices.rst | 4 +++-
 Documentation/admin-guide/devices.txt | 6 +++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst
index e3776d77374b..515338d0e406 100644
--- a/Documentation/admin-guide/devices.rst
+++ b/Documentation/admin-guide/devices.rst
@@ -97,9 +97,11 @@ It is recommended that these links exist on all systems:
 /dev/bttv0	video0		symbolic	Backward compatibility
 /dev/radio	radio0		symbolic	Backward compatibility
 /dev/i2o*	/dev/i2o/*	symbolic	Backward compatibility
-/dev/scd?	sr?		hard		Alternate SCSI CD-ROM name
 =============== =============== =============== ===============================
 
+Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
+ended around year 2011.
+
 Locally defined links
 +++++++++++++++++++++
 
diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index 94c98be1329a..c480f230aa4a 100644
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -389,11 +389,11 @@
 		    ...
 
   11 block	SCSI CD-ROM devices
-		  0 = /dev/scd0		First SCSI CD-ROM
-		  1 = /dev/scd1		Second SCSI CD-ROM
+		  0 = /dev/sr0		First SCSI CD-ROM
+		  1 = /dev/sr1		Second SCSI CD-ROM
 		    ...
 
-		The prefix /dev/sr (instead of /dev/scd) has been deprecated.
+		In the past the prefix /dev/scd (instead of /dev/sr) was used and even recommended.
 
   12 char	QIC-02 tape
 		  2 = /dev/ntpqic11	QIC-11, no rewind-on-close
-- 
2.39.5

Re: [PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Bagas Sanjaya]

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On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
> +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
> +ended around year 2011.

What about "Support for /dev/scd? as alternative names for /dev/sr? has been
removed in 2011"?

Thanks. 

-- 
An old man doll... just what I always wanted! - Clara

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Re: [PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Max Nikulin]

On 29/11/2025 13:13, Bagas Sanjaya wrote:
> On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
>> +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
>> +ended around year 2011.
> 
> What about "Support for /dev/scd? as alternative names for /dev/sr? has been
> removed in 2011"?

If others support your suggestion then I do not mind. Feel free to 
commit preferred variant ignoring my patch.

I would be more verbose however by adding that it was removed namely 
from udev:

Creation of ``/dev/scd?`` alternative names for ``sr?`` CD-ROM and other 
optical drives (using SCSI commands) was removed in ``udev-174`` 
(released in 2011).

Perhaps I am biased by my confusion. Noticed that wodim tries to access 
currently absent /dev/scd0 for kernels >= X.6, I tried git blame game in 
kernel repository to find kernel version when scd<N> were renamed to 
sr<N>. It took some time for me to realize that it is impossible to 
determine scd vs. sr from kernel version. That is why I would consider 
adding explicit mention of udev. Otherwise for me it sounds like that 
scd? names were removed from kernel. I am not a native English speaker, 
so I do not insist on my variant.

How long I should wait for comments before submitting another revision 
of the patch? I hope, pending changes are not an obstacle for those who 
are tempting to review the whole devices.rst file.

Re: [PATCH] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Bagas Sanjaya]

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On Sat, Nov 29, 2025 at 10:01:41PM +0700, Max Nikulin wrote:
> On 29/11/2025 13:13, Bagas Sanjaya wrote:
> > On Sat, Nov 29, 2025 at 12:12:32AM +0700, Max Nikulin wrote:
> > > +Usage of ``/dev/scd?`` as alternate SCSI CD-ROM names for ``sr?`` devices
> > > +ended around year 2011.
> > 
> > What about "Support for /dev/scd? as alternative names for /dev/sr? has been
> > removed in 2011"?
> 
> If others support your suggestion then I do not mind. Feel free to commit
> preferred variant ignoring my patch.
> 
> I would be more verbose however by adding that it was removed namely from
> udev:
> 
> Creation of ``/dev/scd?`` alternative names for ``sr?`` CD-ROM and other
> optical drives (using SCSI commands) was removed in ``udev-174`` (released
> in 2011).

This one looks better.

> 
> Perhaps I am biased by my confusion. Noticed that wodim tries to access
> currently absent /dev/scd0 for kernels >= X.6, I tried git blame game in
> kernel repository to find kernel version when scd<N> were renamed to sr<N>.
> It took some time for me to realize that it is impossible to determine scd
> vs. sr from kernel version. That is why I would consider adding explicit
> mention of udev. Otherwise for me it sounds like that scd? names were
> removed from kernel. I am not a native English speaker, so I do not insist
> on my variant.
> 
> How long I should wait for comments before submitting another revision of
> the patch? I hope, pending changes are not an obstacle for those who are
> tempting to review the whole devices.rst file.

Since we're in rc7 (and 6.18 release is tomorrow), you need to wait until at
least two weeks later (when 6.19 merge window closes) and repost. Don't forget
to Cc me anyway.

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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[PATCH v2 1/2] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Max Nikulin]

Don't claim that /dev/sr<N> device names for SCSI CD-ROM drives are
deprecated and don't recommend /dev/scd<N> alternate names for them.

/dev/scd<N> device names for SCSI CD-ROM drives are not in use for more
than a decade, see commit [1] that was a part of udev release 174.
Earlier, related rules were volatile, sometimes /dev/scd<N> were syminks
to /dev/sr<N>, sometimes vice versa.

Recognizing of root=/dev/scd<N> kernel command line argument was removed
in kernel 2.5.45 [2].

In the docs /dev/scd<N> became recommended names in 2.6.9 [3].
Mention of these names appeared much earlier in 1.3.22 [4].

[1] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?id=d132be4d58
    2011-08-12 14:05:19 +0200 Kay Sievers.
    rules: remove legacy rules for cdrom and usb printer

[2] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/commit/init?h=v2.5.45&id=51924607bd
    2002-10-29 00:47:58 -0800 Alexander Viro.
    [PATCH] removal of root_dev_names[]

[3] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/Documentation/devices.txt?h=v2.6.9-rc4&id=a74e11ffeda
    2004-03-16 15:09:38 -0800 Andrew Morton:
    [PATCH] devices.txt: typos and removal of dead devices

[4] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/tree/Documentation/devices.txt?h=v2.6.9-rc4&id=8f0ec1f9369
    1995-09-01 Linus Torvalds: Import 1.3.22

Signed-off-by: Max Nikulin <manikulin@gmail.com>

---

I hope, the suggested changes make kernel docs more close to reality.

During discussion of a bug in wodim (a fork of cdrecord) I was confused
that docs recommend /dev/scd<N> as SCSI CD-ROM name. The following
thread did not clarify the issue:

https://lore.kernel.org/lkml/20061105100926.GA2883@pelagius.h-e-r-e-s-y.com/
Scsi cdrom naming confusion; sr or scd? Sun, 5 Nov 2006 10:09:26 +0000

If I'm not mistaken, "sr" was always used internally in the driver
while "scd" were limited to log strings. I have added SCSI subsystem
to CC to confirm that there is no objection from their side.

It seems, de-facto /dev/sr<N> names are used and I think, /dev/scd<N>
should be avoided. I may be completely wrong though.

I wouldn't mind if you discard this patch and to commit another one
with better wording instead.

Patch v2:
- More verbose note on removal of /dev/scd? names.
---
 Documentation/admin-guide/devices.rst | 5 ++++-
 Documentation/admin-guide/devices.txt | 6 +++---
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst
index e3776d77374b..0dc8c5b98e30 100644
--- a/Documentation/admin-guide/devices.rst
+++ b/Documentation/admin-guide/devices.rst
@@ -97,9 +97,12 @@ It is recommended that these links exist on all systems:
 /dev/bttv0	video0		symbolic	Backward compatibility
 /dev/radio	radio0		symbolic	Backward compatibility
 /dev/i2o*	/dev/i2o/*	symbolic	Backward compatibility
-/dev/scd?	sr?		hard		Alternate SCSI CD-ROM name
 =============== =============== =============== ===============================
 
+Suggested earlier ``/dev/scd?`` alternative names for ``/dev/sr?``
+CD-ROM and other optical drives (using SCSI commands) were removed
+in ``udev`` version 174 that was released in 2011.
+
 Locally defined links
 +++++++++++++++++++++
 
diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt
index 94c98be1329a..c480f230aa4a 100644
--- a/Documentation/admin-guide/devices.txt
+++ b/Documentation/admin-guide/devices.txt
@@ -389,11 +389,11 @@
 		    ...
 
   11 block	SCSI CD-ROM devices
-		  0 = /dev/scd0		First SCSI CD-ROM
-		  1 = /dev/scd1		Second SCSI CD-ROM
+		  0 = /dev/sr0		First SCSI CD-ROM
+		  1 = /dev/sr1		Second SCSI CD-ROM
 		    ...
 
-		The prefix /dev/sr (instead of /dev/scd) has been deprecated.
+		In the past the prefix /dev/scd (instead of /dev/sr) was used and even recommended.
 
   12 char	QIC-02 tape
 		  2 = /dev/ntpqic11	QIC-11, no rewind-on-close

base-commit: 464257baf99200d1be1c053f15aa617056361e81
-- 
2.39.5

[PATCH v2 2/2] docs: admin: devices: remove /dev/cdwriter

[Max Nikulin]

Remove /dev/cdwriter from the local symlinks table and change the
related note that this alias was removed long time ago.

Creation of the symlink was removed from udev in commit [1] that
became a part of release 115 in 2007 [2].

The altered text was added in 1995 [3].

[1] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?id=b1a2b83f2d
    2007-08-11 14:06:03 +0200 Kay Sievers.
    rules: update Fedora rules

[2] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?h=7e599863919
    2007-08-24 01:29:54 +0200 Kay Sievers.
    release 115

[3] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/Documentation/devices.txt?h=v2.5.45&id=6e995ea941a
    1995-11-21 Linus Torvalds.
    Import 1.3.43

Signed-off-by: Max Nikulin <manikulin@gmail.com>

---

I hope, I have not missed something important and this patch removes
another discrepancy of documentation and current contents of the /dev
directory.

I wouldn't mind if you discard this patch and to commit another one
with better wording instead.

Earlier I submitted first variant of the /dev/sdc<N> patch without this
chunk.
---
 Documentation/admin-guide/devices.rst | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst
index 0dc8c5b98e30..842f9e503760 100644
--- a/Documentation/admin-guide/devices.rst
+++ b/Documentation/admin-guide/devices.rst
@@ -115,7 +115,6 @@ exist, they should have the following uses.
 /dev/mouse	mouse port	symbolic	Current mouse device
 /dev/tape	tape device	symbolic	Current tape device
 /dev/cdrom	CD-ROM device	symbolic	Current CD-ROM device
-/dev/cdwriter	CD-writer	symbolic	Current CD-writer device
 /dev/scanner	scanner		symbolic	Current scanner device
 /dev/modem	modem port	symbolic	Current dialout device
 /dev/root	root device	symbolic	Current root filesystem
@@ -129,8 +128,11 @@ exists, ``/dev/modem`` should point to the appropriate primary TTY device
 
 For SCSI devices, ``/dev/tape`` and ``/dev/cdrom`` should point to the
 *cooked* devices (``/dev/st*`` and ``/dev/sr*``, respectively), whereas
-``/dev/cdwriter`` and /dev/scanner should point to the appropriate generic
-SCSI devices (/dev/sg*).
+``/dev/scanner`` should point to the appropriate generic
+SCSI device (``/dev/sg*``).  In the past the current CD-writer drive
+had the ``/dev/cdwriter`` convenience symbolic link to a ``/dev/sg*``
+generic SCSI device, but its creation was removed in ``udev`` version 115
+released in 2007.
 
 ``/dev/mouse`` may point to a primary serial TTY device, a hardware mouse
 device, or a socket for a mouse driver program (e.g. ``/dev/gpmdata``).
-- 
2.39.5

Re: [PATCH v2 1/2] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Martin K. Petersen]

Max,

> Don't claim that /dev/sr<N> device names for SCSI CD-ROM drives are
> deprecated and don't recommend /dev/scd<N> alternate names for them.

OK with me. I haven't seen /dev/scd in use for a very long time.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>

-- 
Martin K. Petersen

Re: [PATCH v2 1/2] docs: admin: devices: /dev/sr<N> for SCSI CD-ROM

[Jonathan Corbet]

Max Nikulin <manikulin@gmail.com> writes:

> Don't claim that /dev/sr<N> device names for SCSI CD-ROM drives are
> deprecated and don't recommend /dev/scd<N> alternate names for them.
>
> /dev/scd<N> device names for SCSI CD-ROM drives are not in use for more
> than a decade, see commit [1] that was a part of udev release 174.
> Earlier, related rules were volatile, sometimes /dev/scd<N> were syminks
> to /dev/sr<N>, sometimes vice versa.
>
> Recognizing of root=/dev/scd<N> kernel command line argument was removed
> in kernel 2.5.45 [2].
>
> In the docs /dev/scd<N> became recommended names in 2.6.9 [3].
> Mention of these names appeared much earlier in 1.3.22 [4].

I've applied this one, thanks.

jon

Re: [PATCH v2 2/2] docs: admin: devices: remove /dev/cdwriter

[Jonathan Corbet]

Max Nikulin <manikulin@gmail.com> writes:

> Remove /dev/cdwriter from the local symlinks table and change the
> related note that this alias was removed long time ago.
>
> Creation of the symlink was removed from udev in commit [1] that
> became a part of release 115 in 2007 [2].
>
[...]
>  
>  For SCSI devices, ``/dev/tape`` and ``/dev/cdrom`` should point to the
>  *cooked* devices (``/dev/st*`` and ``/dev/sr*``, respectively), whereas
> -``/dev/cdwriter`` and /dev/scanner should point to the appropriate generic
> -SCSI devices (/dev/sg*).
> +``/dev/scanner`` should point to the appropriate generic
> +SCSI device (``/dev/sg*``).  In the past the current CD-writer drive
> +had the ``/dev/cdwriter`` convenience symbolic link to a ``/dev/sg*``
> +generic SCSI device, but its creation was removed in ``udev`` version 115
> +released in 2007.

As a general rule, kernel documentation should describe the kernel we
have now; if we try to fill it with all of the history of what once was,
the end result will not be pleasing.  So can I get a version just
removing the obsolete material?

Thanks,

jon

[PATCH v3] docs: admin: devices: remove /dev/cdwriter

[Max Nikulin]

Remove /dev/cdwriter from the local symlinks table and from the related
note.

Creation of the symlink was removed from udev in commit [1] that
became a part of release 115 in 2007 [2].

The altered text was added in 1995 [3].

[1] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?id=b1a2b83f2d
    2007-08-11 14:06:03 +0200 Kay Sievers.
    rules: update Fedora rules

[2] https://git.kernel.org/pub/scm/linux/hotplug/udev.git/commit/?h=7e599863919
    2007-08-24 01:29:54 +0200 Kay Sievers.
    release 115

[3] https://git.kernel.org/pub/scm/linux/kernel/git/history/history.git/diff/Documentation/devices.txt?h=v2.5.45&id=6e995ea941a
    1995-11-21 Linus Torvalds.
    Import 1.3.43

Signed-off-by: Max Nikulin <manikulin@gmail.com>

---

Patch set v3 (second revision of this patch) changes:
- do not add comment when cdwriter was removed from udev,
- adjust commit message accordingly.

Despite in this particular case I disagree with

Jonathan Corbet Mon, 22 Dec 2025 14:58:25 -0700 wrote:
> As a general rule, kernel documentation should describe the kernel we
> have now; if we try to fill it with all of the history of what once was,
> the end result will not be pleasing.

- The note was related to recommendations to other projects rather than
  documenting kernel.
- The obsolete recommendation was here for too long time, so it is
  better to keep the reason to change for some period of time.
  It may help to those who seen "cdwriter" earlier and now they may be
  confused.  On the other hand the change is minor and there is no point
  to prominently advertise it.
- Git history is incomplete making "git blame" game not so trivial.

> So can I get a version just
> removing the obsolete material?

Earlier I added the following exactly for this case.  The change is
minor, so alternative commit may save some time.

> > I wouldn't mind if you discard this patch and to commit another one
> > with better wording instead.
---
 Documentation/admin-guide/devices.rst | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/Documentation/admin-guide/devices.rst b/Documentation/admin-guide/devices.rst
index 0dc8c5b98e30..b103ba52776a 100644
--- a/Documentation/admin-guide/devices.rst
+++ b/Documentation/admin-guide/devices.rst
@@ -115,7 +115,6 @@ exist, they should have the following uses.
 /dev/mouse	mouse port	symbolic	Current mouse device
 /dev/tape	tape device	symbolic	Current tape device
 /dev/cdrom	CD-ROM device	symbolic	Current CD-ROM device
-/dev/cdwriter	CD-writer	symbolic	Current CD-writer device
 /dev/scanner	scanner		symbolic	Current scanner device
 /dev/modem	modem port	symbolic	Current dialout device
 /dev/root	root device	symbolic	Current root filesystem
@@ -129,8 +128,8 @@ exists, ``/dev/modem`` should point to the appropriate primary TTY device
 
 For SCSI devices, ``/dev/tape`` and ``/dev/cdrom`` should point to the
 *cooked* devices (``/dev/st*`` and ``/dev/sr*``, respectively), whereas
-``/dev/cdwriter`` and /dev/scanner should point to the appropriate generic
-SCSI devices (/dev/sg*).
+``/dev/scanner`` should point to the appropriate generic
+SCSI device (``/dev/sg*``).
 
 ``/dev/mouse`` may point to a primary serial TTY device, a hardware mouse
 device, or a socket for a mouse driver program (e.g. ``/dev/gpmdata``).

base-commit: 7f3c3a0a9103dc92c823f27db3284ac2914e7558
-- 
2.39.5

Re: [PATCH v3] docs: admin: devices: remove /dev/cdwriter

[Jonathan Corbet]

Max Nikulin <manikulin@gmail.com> writes:

> Remove /dev/cdwriter from the local symlinks table and from the related
> note.
>
> Creation of the symlink was removed from udev in commit [1] that
> became a part of release 115 in 2007 [2].
>
> The altered text was added in 1995 [3].

Applied, thanks.

jon

Re: [PATCH v2 2/2] docs: admin: devices: remove /dev/cdwriter

[Max Nikulin]

Thank you for your work on kernel docs.

Feel free to ignore the following comment.

On 23/12/2025 4:58 am, Jonathan Corbet wrote:
> 
> As a general rule, kernel documentation should describe the kernel we
> have now; if we try to fill it with all of the history of what once was,
> the end result will not be pleasing.

Actually I was considering adding a history section at the end of
Documentation/admin-guide/devices.rst. It seems, mentions of LANANA and 
FHS in opening paragraphs are not actual any more. I have not noticed 
references to the devices doc in the latest revision of FHS. The note on 
LANANA was important a decade ago when it was added.

Currently perhaps it is better to move these remarks to the end of the 
document. They will be available for search engines, effort invested 
into maintenance of that docs in the past is recognized, but these 
references will not distract readers interested in current state of affairs.

Mentions of /dev/scd<N> and /dev/cdwriter may be moved to the new 
section on history as well. The idea to to help those, who find old 
device names in old docs or code, to resolve their uncertainty.

I have no plan to submit more patches though.