symbolic links on Paragon Linux File systems

symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

Hi all

There is a commercial ext3-4 file system driver for windowsLinux File Systems für Windows | Paragon Softwarewhich enable Windows to read an write on native ext3-4 volumes.In General cygwin works perfectly on such volumes,even named pipes work,
but Cygwin programs do not interprete those links correctly,which are created on such volumes.whilst symbolic links on native NTFS drives referring files on such volumeswork perfectly.
$pwd/cygdrive/e

$ echo hallo > source

$ ln -s source sl

$ cat sl
!<symlink>▒▒source









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Re: symbolic links on Paragon Linux File systems

[Corinna Vinschen]

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On Dec 17 08:11, Simon Liesenfeld via cygwin wrote:
> Hi all
> 
> There is a commercial ext3-4 file system driver for windowsLinux File
> Systems für Windows | Paragon Softwarewhich enable Windows to read an
> write on native ext3-4 volumes.In General cygwin works perfectly on
> such volumes,even named pipes work,
> but Cygwin programs do not interprete those links correctly,which are
> created on such volumes.whilst symbolic links on native NTFS drives
> referring files on such volumeswork perfectly.
> $pwd/cygdrive/e
> 
> $ echo hallo > source
> 
> $ ln -s source sl
> 
> $ cat sl
> !<symlink>▒▒source

Yes, we can't do that without special knowledge of the FS.  The default
symlinks on Cygwin are only evaluated correctly if the DOS SYSTEM
attribute is set.  The ext4 driver can't do that, obviously.

Are the native symlinks on an ext4 FS converted to NTFS symlinks
on the fly by the driver?  Are they visible as symlinks in Windows
or Cygwin?

If so, you could try setting the environment variable CYGWIN to contain
"winsymlinks:native".  This creates native Windows symlinks rather than
the special Cygwin POSIX symlinks.  If the driver is handling this
correctly, it should transparently convert them to ext4 symlinks and
they should just work.


HTH,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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Re: symbolic links on Paragon Linux File systems

[Corinna Vinschen]

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On Dec 17 10:34, Corinna Vinschen wrote:
> On Dec 17 08:11, Simon Liesenfeld via cygwin wrote:
> > Hi all
> > 
> > There is a commercial ext3-4 file system driver for windowsLinux File
> > Systems für Windows | Paragon Softwarewhich enable Windows to read an
> > write on native ext3-4 volumes.In General cygwin works perfectly on
> > such volumes,even named pipes work,
> > but Cygwin programs do not interprete those links correctly,which are
> > created on such volumes.whilst symbolic links on native NTFS drives
> > referring files on such volumeswork perfectly.
> > $pwd/cygdrive/e
> > 
> > $ echo hallo > source
> > 
> > $ ln -s source sl
> > 
> > $ cat sl
> > !<symlink>▒▒source
> 
> Yes, we can't do that without special knowledge of the FS.  The default
> symlinks on Cygwin are only evaluated correctly if the DOS SYSTEM
> attribute is set.  The ext4 driver can't do that, obviously.
> 
> Are the native symlinks on an ext4 FS converted to NTFS symlinks
> on the fly by the driver?  Are they visible as symlinks in Windows
> or Cygwin?
> 
> If so, you could try setting the environment variable CYGWIN to contain
> "winsymlinks:native".  This creates native Windows symlinks rather than
> the special Cygwin POSIX symlinks.  If the driver is handling this
> correctly, it should transparently convert them to ext4 symlinks and
> they should just work.
> 
> 
> HTH,
> Corinna

Btw., we might be able to do more.  Can you do me a favor and call

  /lib/csih/getVolInfo <path to any file on the ext4 FS>
  
and paste the result in your reply to the maling list?  Just for
comparison, it should look roughly like this (example native NTFS):

Device Type        : 7
Characteristics    : 20020
Volume Name        : <>
Serial Number      : 3327928886
Max Filenamelength : 255
Filesystemname     : <NTFS>
Flags              : 3e706ff
  FILE_CASE_SENSITIVE_SEARCH  : TRUE
  FILE_CASE_PRESERVED_NAMES   : TRUE
  FILE_UNICODE_ON_DISK        : TRUE
  FILE_PERSISTENT_ACLS        : TRUE
  FILE_FILE_COMPRESSION       : TRUE
  FILE_VOLUME_QUOTAS          : TRUE
  FILE_SUPPORTS_SPARSE_FILES  : TRUE
  FILE_SUPPORTS_REPARSE_POINTS: TRUE
  FILE_SUPPORTS_REMOTE_STORAGE: FALSE
  FILE_VOLUME_IS_COMPRESSED   : FALSE
  FILE_SUPPORTS_OBJECT_IDS    : TRUE
  FILE_SUPPORTS_ENCRYPTION    : TRUE
  FILE_NAMED_STREAMS          : TRUE
  FILE_READ_ONLY_VOLUME       : FALSE
  FILE_SEQUENTIAL_WRITE_ONCE  : FALSE
  FILE_SUPPORTS_TRANSACTIONS  : TRUE

Maybe we can tweak Cygwin to handle the Paragon ext4 driver out of
the box.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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Re: symbolic links on Paragon Linux File systems

[Andrey Repin]

Greetings, Simon Liesenfeld!

> Hi all

> There is a commercial ext3-4 file system driver for windowsLinux File
> Systems für Windows | Paragon Softwarewhich enable Windows to read an write
> on native ext3-4 volumes.In General cygwin works perfectly on such volumes,even named pipes work,
> but Cygwin programs do not interprete those links correctly,which are
> created on such volumes.whilst symbolic links on native NTFS drives
> referring files on such volumeswork perfectly.
> $pwd/cygdrive/e

> $ echo hallo > source

> $ ln -s source sl

> $ cat sl
> !<symlink>▒▒source

What doe /usr/lib/csih/getVolInfo say about such volume?


-- 
With best regards,
Andrey Repin
Monday, December 17, 2018 14:28:48

Sorry for my terrible english...
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Re: symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

 Hi all,
Thank you so much for the response,and nearby for the entire cygwin Project.(Best of both worlds)"The devil is in the detail"I admire cygwin so much, and I' am overwhelmed
that it can do the named pipes on paragon systemalready.I do not expect cygwin to master the symbolic links,it's too much.But if it were able master, I would sit on my chair breathless.
One can download paragon athttps://www.paragon-software.com/de/home/linuxfs-windows/#
it has a ten days trial period.

 /usr/lib/csih/getVolInfo /cygdrive/e
Device Type        : 7Characteristics    : 20
Volume Name        : <>
Serial Number      : 4229931105
Max Filenamelength : 260
Filesystemname     : <ext4>
Flags              : 107
  FILE_CASE_SENSITIVE_SEARCH  : TRUE
  FILE_CASE_PRESERVED_NAMES   : TRUE
  FILE_UNICODE_ON_DISK        : TRUE
  FILE_PERSISTENT_ACLS        : FALSE
  FILE_FILE_COMPRESSION       : FALSE
  FILE_VOLUME_QUOTAS          : FALSE
  FILE_SUPPORTS_SPARSE_FILES  : FALSE
  FILE_SUPPORTS_REPARSE_POINTS: FALSE
  FILE_SUPPORTS_REMOTE_STORAGE: TRUE
  FILE_VOLUME_IS_COMPRESSED   : FALSE
  FILE_SUPPORTS_OBJECT_IDS    : FALSE
  FILE_SUPPORTS_ENCRYPTION    : FALSE
  FILE_NAMED_STREAMS          : FALSE
  FILE_READ_ONLY_VOLUME       : FALSE
  FILE_SEQUENTIAL_WRITE_ONCE  : FALSE
  FILE_SUPPORTS_TRANSACTIONS  : FALSE



    On Monday, December 17, 2018, 12:35:02 PM GMT+1, Andrey Repin <anrdaemon@yandex.ru> wrote:  
 
 Greetings, Simon Liesenfeld!

> Hi all

> There is a commercial ext3-4 file system driver for windowsLinux File
> Systems für Windows | Paragon Softwarewhich enable Windows to read an write
> on native ext3-4 volumes.In General cygwin works perfectly on such volumes,even named pipes work,
> but Cygwin programs do not interprete those links correctly,which are
> created on such volumes.whilst symbolic links on native NTFS drives
> referring files on such volumeswork perfectly.
> $pwd/cygdrive/e

> $ echo hallo > source

> $ ln -s source sl

> $ cat sl
> !<symlink>▒▒source

What doe /usr/lib/csih/getVolInfo say about such volume?


-- 
With best regards,
Andrey Repin
Monday, December 17, 2018 14:28:48

Sorry for my terrible english...  
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Re: symbolic links on Paragon Linux File systems

[Corinna Vinschen]

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On Dec 17 12:03, Simon Liesenfeld via cygwin wrote:
>  Hi all,
> Thank you so much for the response,and nearby for the entire cygwin
> Project.(Best of both worlds)"The devil is in the detail"I admire
> cygwin so much, and I' am overwhelmed
> that it can do the named pipes on paragon systemalready.I do not
> expect cygwin to master the symbolic links,it's too much.But if it
> were able master, I would sit on my chair breathless.
> One can download paragon athttps://www.paragon-software.com/de/home/linuxfs-windows/#
> it has a ten days trial period.
> 
>  /usr/lib/csih/getVolInfo /cygdrive/e
> Device Type        : 7Characteristics    : 20
> Volume Name        : <>
> Serial Number      : 4229931105
> Max Filenamelength : 260
> Filesystemname     : <ext4>
> Flags              : 107
>   FILE_CASE_SENSITIVE_SEARCH  : TRUE
>   FILE_CASE_PRESERVED_NAMES   : TRUE
>   FILE_UNICODE_ON_DISK        : TRUE
>   FILE_PERSISTENT_ACLS        : FALSE
>   FILE_FILE_COMPRESSION       : FALSE
>   FILE_VOLUME_QUOTAS          : FALSE
>   FILE_SUPPORTS_SPARSE_FILES  : FALSE
>   FILE_SUPPORTS_REPARSE_POINTS: FALSE
>   FILE_SUPPORTS_REMOTE_STORAGE: TRUE
>   FILE_VOLUME_IS_COMPRESSED   : FALSE
>   FILE_SUPPORTS_OBJECT_IDS    : FALSE
>   FILE_SUPPORTS_ENCRYPTION    : FALSE
>   FILE_NAMED_STREAMS          : FALSE
>   FILE_READ_ONLY_VOLUME       : FALSE
>   FILE_SEQUENTIAL_WRITE_ONCE  : FALSE
>   FILE_SUPPORTS_TRANSACTIONS  : FALSE

What about my question in https://cygwin.com/ml/cygwin/2018-12/msg00135.html?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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Re: symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

 Hi Corinna,I 've set in the Control Panel,and  this reflects in bash.I still does work.
$ set | grep -i nativeCYGWIN=winsymlinks:native

$ ln -s /cygdrive/e/source sl

$ cat sl
!<symlink>▒▒/cygdrive/e/source

One can download a 10 days trial version at:
http://dl.paragon-software.com/demo/linuxwin_trial.msi or buy for about 19 € 
    On Monday, December 17, 2018, 4:46:37 PM GMT+1, Simon Liesenfeld <surgeonde@yahoo.de> wrote:  
 
  Hi Corinna,I 've set in the Contrpl Panel,es this reflects in bash.I still does work.
$ set | grep -i nativeCYGWIN=winsymlinks:native

$ ln -s /cygdrive/e/source sl

$ cat sl
!<symlink>▒▒/cygdrive/e/source





    On Monday, December 17, 2018, 1:04:21 PM GMT+1, Simon Liesenfeld via cygwin <cygwin@cygwin.com> wrote:  
 
  Hi all,
Thank you so much for the response,and nearby for the entire cygwin Project.(Best of both worlds)"The devil is in the detail"I admire cygwin so much, and I' am overwhelmed
that it can do the named pipes on paragon systemalready.I do not expect cygwin to master the symbolic links,it's too much.But if it were able master, I would sit on my chair breathless.
One can download paragon athttps://www.paragon-software.com/de/home/linuxfs-windows/#
it has a ten days trial period.

 /usr/lib/csih/getVolInfo /cygdrive/e
Device Type        : 7Characteristics    : 20
Volume Name        : <>
Serial Number      : 4229931105
Max Filenamelength : 260
Filesystemname     : <ext4>
Flags              : 107
  FILE_CASE_SENSITIVE_SEARCH  : TRUE
  FILE_CASE_PRESERVED_NAMES   : TRUE
  FILE_UNICODE_ON_DISK        : TRUE
  FILE_PERSISTENT_ACLS        : FALSE
  FILE_FILE_COMPRESSION       : FALSE
  FILE_VOLUME_QUOTAS          : FALSE
  FILE_SUPPORTS_SPARSE_FILES  : FALSE
  FILE_SUPPORTS_REPARSE_POINTS: FALSE
  FILE_SUPPORTS_REMOTE_STORAGE: TRUE
  FILE_VOLUME_IS_COMPRESSED   : FALSE
  FILE_SUPPORTS_OBJECT_IDS    : FALSE
  FILE_SUPPORTS_ENCRYPTION    : FALSE
  FILE_NAMED_STREAMS          : FALSE
  FILE_READ_ONLY_VOLUME       : FALSE
  FILE_SEQUENTIAL_WRITE_ONCE  : FALSE
  FILE_SUPPORTS_TRANSACTIONS  : FALSE



    On Monday, December 17, 2018, 12:35:02 PM GMT+1, Andrey Repin <anrdaemon@yandex.ru> wrote:  
 
 Greetings, Simon Liesenfeld!

> Hi all

> There is a commercial ext3-4 file system driver for windowsLinux File
> Systems für Windows | Paragon Softwarewhich enable Windows to read an write
> on native ext3-4 volumes.In General cygwin works perfectly on such volumes,even named pipes work,
> but Cygwin programs do not interprete those links correctly,which are
> created on such volumes.whilst symbolic links on native NTFS drives
> referring files on such volumeswork perfectly.
> $pwd/cygdrive/e

> $ echo hallo > source

> $ ln -s source sl

> $ cat sl
> !<symlink>▒▒source

What doe /usr/lib/csih/getVolInfo say about such volume?


-- 
With best regards,
Andrey Repin
Monday, December 17, 2018 14:28:48

Sorry for my terrible english...  
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Re: symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

 Hi Corinna,I 've set in the Control Panel,and  this reflects in bash.I still does work.
$ set | grep -i nativeCYGWIN=winsymlinks:native

$ ln -s /cygdrive/e/source sl

$ cat sl
!<symlink>▒▒/cygdrive/e/source

One can download a 10 days trial version at:
http://dl.paragon-software.com/demo/linuxwin_trial.msi or buy for about 19 € 
    On Monday, December 17, 2018, 4:46:37 PM GMT+1, Simon Liesenfeld <surgeonde@yahoo.de> wrote:  
 
  Hi Corinna,I 've set in the Contrpl Panel,es this reflects in bash.I still does work.
$ set | grep -i nativeCYGWIN=winsymlinks:native

$ ln -s /cygdrive/e/source sl

$ cat sl
!<symlink>▒▒/cygdrive/e/source





    On Monday, December 17, 2018, 1:04:21 PM GMT+1, Simon Liesenfeld via cygwin <cygwin@cygwin.com> wrote:  
 
  Hi all,
Thank you so much for the response,and nearby for the entire cygwin Project.(Best of both worlds)"The devil is in the detail"I admire cygwin so much, and I' am overwhelmed
that it can do the named pipes on paragon systemalready.I do not expect cygwin to master the symbolic links,it's too much.But if it were able master, I would sit on my chair breathless.
One can download paragon athttps://www.paragon-software.com/de/home/linuxfs-windows/#
it has a ten days trial period.

 /usr/lib/csih/getVolInfo /cygdrive/e
Device Type        : 7Characteristics    : 20
Volume Name        : <>
Serial Number      : 4229931105
Max Filenamelength : 260
Filesystemname     : <ext4>
Flags              : 107
  FILE_CASE_SENSITIVE_SEARCH  : TRUE
  FILE_CASE_PRESERVED_NAMES   : TRUE
  FILE_UNICODE_ON_DISK        : TRUE
  FILE_PERSISTENT_ACLS        : FALSE
  FILE_FILE_COMPRESSION       : FALSE
  FILE_VOLUME_QUOTAS          : FALSE
  FILE_SUPPORTS_SPARSE_FILES  : FALSE
  FILE_SUPPORTS_REPARSE_POINTS: FALSE
  FILE_SUPPORTS_REMOTE_STORAGE: TRUE
  FILE_VOLUME_IS_COMPRESSED   : FALSE
  FILE_SUPPORTS_OBJECT_IDS    : FALSE
  FILE_SUPPORTS_ENCRYPTION    : FALSE
  FILE_NAMED_STREAMS          : FALSE
  FILE_READ_ONLY_VOLUME       : FALSE
  FILE_SEQUENTIAL_WRITE_ONCE  : FALSE
  FILE_SUPPORTS_TRANSACTIONS  : FALSE



    On Monday, December 17, 2018, 12:35:02 PM GMT+1, Andrey Repin <anrdaemon@yandex.ru> wrote:  
 
 Greetings, Simon Liesenfeld!

> Hi all

> There is a commercial ext3-4 file system driver for windowsLinux File
> Systems für Windows | Paragon Softwarewhich enable Windows to read an write
> on native ext3-4 volumes.In General cygwin works perfectly on such volumes,even named pipes work,
> but Cygwin programs do not interprete those links correctly,which are
> created on such volumes.whilst symbolic links on native NTFS drives
> referring files on such volumeswork perfectly.
> $pwd/cygdrive/e

> $ echo hallo > source

> $ ln -s source sl

> $ cat sl
> !<symlink>▒▒source

What doe /usr/lib/csih/getVolInfo say about such volume?


-- 
With best regards,
Andrey Repin
Monday, December 17, 2018 14:28:48

Sorry for my terrible english...  
--
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Re: symbolic links on Paragon Linux File systems

[Corinna Vinschen]

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On Dec 17 10:34, Corinna Vinschen wrote:
> On Dec 17 08:11, Simon Liesenfeld via cygwin wrote:
> > Hi all
> > 
> > There is a commercial ext3-4 file system driver for windowsLinux File
> > Systems für Windows | Paragon Softwarewhich enable Windows to read an
> > write on native ext3-4 volumes.In General cygwin works perfectly on
> > such volumes,even named pipes work,
> > but Cygwin programs do not interprete those links correctly,which are
> > created on such volumes.whilst symbolic links on native NTFS drives
> > referring files on such volumeswork perfectly.
> > $pwd/cygdrive/e
> > 
> > $ echo hallo > source
> > 
> > $ ln -s source sl
> > 
> > $ cat sl
> > !<symlink>▒▒source
> 
> Yes, we can't do that without special knowledge of the FS.  The default
> symlinks on Cygwin are only evaluated correctly if the DOS SYSTEM
> attribute is set.  The ext4 driver can't do that, obviously.
> 
> Are the native symlinks on an ext4 FS converted to NTFS symlinks
> on the fly by the driver?  Are they visible as symlinks in Windows
> or Cygwin?
> 
> If so, you could try setting the environment variable CYGWIN to contain
> "winsymlinks:native".  This creates native Windows symlinks rather than
> the special Cygwin POSIX symlinks.  If the driver is handling this
> correctly, it should transparently convert them to ext4 symlinks and
> they should just work.

Answering my own questions:

No, the driver does not handle symlinks gracefully *at all*.

- Existing symlinks on the FS are handled as if they are simple files.
  They are in no way identifiable as symlinks by any Windows client.
  They supposedly only contain the name of the symlink target, which is
  an arbitrary string.  No symlink marker or anything.

- DOS file attributes don't work, so we can't use Cygwin's symlink
  handling, not even by utilizing Windows shortcuts instead of Cygwin
  symlinks.

- Windows native symlinks and transparent conversion to and from ext4
  symlinks is not supported.

- No ACL handling, not even to fake basic POSIX permissions, so we can't
  change the permissions at all.

I don't think it's worth to go to great length supporting Cygwin
symlinks on this FS.  They won't be recognized by your Linux
installation as symlinks anyway and we'd have to perform excessively
slow checks just to recognize them.

As a sidenote, the OSS project Ext2Fsd handles symlinks transparently
via standard Windows functions.  With "CYGWIN=winsymlinks:native" you
can generate real ext4 symlinks transparently.  Even the good old Cygwin
symlink works on Cygwin without programmatic intervention, albeit those
won't be recognized as symlinks by Linux of course.  Unfortunately
Ext2Fsd didn't learn to handle ext4 with the 64bit FS option set yet.
64bit is default for quite some time.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer

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Re: symbolic links on Paragon Linux File systems

[Stefan Baur]

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Am 17.12.18 um 17:57 schrieb Corinna Vinschen:
> As a sidenote, the OSS project Ext2Fsd handles symlinks transparently
> via standard Windows functions.  With "CYGWIN=winsymlinks:native" you
> can generate real ext4 symlinks transparently.  Even the good old Cygwin
> symlink works on Cygwin without programmatic intervention, albeit those
> won't be recognized as symlinks by Linux of course.  Unfortunately
> Ext2Fsd didn't learn to handle ext4 with the 64bit FS option set yet.
> 64bit is default for quite some time.

Hmm, their website says:

> *Ext2Fsd 0.69 released !*
> November 2nd, 2017
> 
> WARNINGS:
> 
>     Don't use Ext2Fsd 0.68 or earlier versions with latest Ubuntu or
>     Debian systems. Ext2Fsd 0.68 cannot process EXT4 with 64-BIT mode
>     enabled, then it could corrupt your data. Very sorry for this
>     disaster issue, I'm working on an improvement.
> 
> Features implemented and bugfix:
> 
>     1, FIXME: superblock corruption of EXT4 volumes with 64BIT mode enabled 
>     2, FIXME: possible corruption by race conditions in buffer-head reapering
>     3, FIXME: possible deadlock issues (when flushing) caused by BCB locks
>     4, FIXME: miscellaneous minor updates of Ext2Fsd code base

Sooo ... if the warning only applies for 0.68 and earlier versions,
while the current version is 0.69, as the headline says, I'd be tempted
to believe they fixed that issue.

-Stefan

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Re: symbolic links on Paragon Linux File systems

[Stefan Baur]

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Am 17.12.18 um 19:45 schrieb Stefan Baur:

>> Features implemented and bugfix:
>>
>>     1, FIXME: superblock corruption of EXT4 volumes with 64BIT mode enabled 
>>     2, FIXME: possible corruption by race conditions in buffer-head reapering
>>     3, FIXME: possible deadlock issues (when flushing) caused by BCB locks
>>     4, FIXME: miscellaneous minor updates of Ext2Fsd code base
> 
> Sooo ... if the warning only applies for 0.68 and earlier versions,
> while the current version is 0.69, as the headline says, I'd be tempted
> to believe they fixed that issue.

Ah, dangit, forget what I wrote, at the bottom it says

> Unsupported Ext3/4 features:
> 
>   1, 64BIT mode (to support 2^64 blocks)
[...]

So it's still not supported, it just doesn't damage your superblock any
more.

-Stefan



-- 
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Geschäftsführer: Stefan Baur
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Fon/Fax 0731 40 34 66-36/-35 | USt-IdNr.: DE268653243


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Re: symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

 Hi Corinna,
since you answered your own questionsI can better understand my own stupidity.I have created now a hard and a soft link with a native linux,then I booted Windows, started the paragon driver,then cygwin  programs as well as any dos program perfectly 
understood the links.
Even if cygwin were able to understand its own links on paragon volumes,they would not be understood when running the volume by linux again.That does not make sense.
May be there is a command line option from paragonto create links.

Thank you so much Corinna.


    On Monday, December 17, 2018, 5:57:43 PM GMT+1, Corinna Vinschen <corinna-cygwin@cygwin.com> wrote:  
 
 On Dec 17 10:34, Corinna Vinschen wrote:
> On Dec 17 08:11, Simon Liesenfeld via cygwin wrote:
> > Hi all
> > 
> > There is a commercial ext3-4 file system driver for windowsLinux File
> > Systems für Windows | Paragon Softwarewhich enable Windows to read an
> > write on native ext3-4 volumes.In General cygwin works perfectly on
> > such volumes,even named pipes work,
> > but Cygwin programs do not interprete those links correctly,which are
> > created on such volumes.whilst symbolic links on native NTFS drives
> > referring files on such volumeswork perfectly.
> > $pwd/cygdrive/e
> > 
> > $ echo hallo > source
> > 
> > $ ln -s source sl
> > 
> > $ cat sl
> > !<symlink>▒▒source
> 
> Yes, we can't do that without special knowledge of the FS.  The default
> symlinks on Cygwin are only evaluated correctly if the DOS SYSTEM
> attribute is set.  The ext4 driver can't do that, obviously.
> 
> Are the native symlinks on an ext4 FS converted to NTFS symlinks
> on the fly by the driver?  Are they visible as symlinks in Windows
> or Cygwin?
> 
> If so, you could try setting the environment variable CYGWIN to contain
> "winsymlinks:native".  This creates native Windows symlinks rather than
> the special Cygwin POSIX symlinks.  If the driver is handling this
> correctly, it should transparently convert them to ext4 symlinks and
> they should just work.

Answering my own questions:

No, the driver does not handle symlinks gracefully *at all*.

- Existing symlinks on the FS are handled as if they are simple files.
  They are in no way identifiable as symlinks by any Windows client.
  They supposedly only contain the name of the symlink target, which is
  an arbitrary string.  No symlink marker or anything.

- DOS file attributes don't work, so we can't use Cygwin's symlink
  handling, not even by utilizing Windows shortcuts instead of Cygwin
  symlinks.

- Windows native symlinks and transparent conversion to and from ext4
  symlinks is not supported.

- No ACL handling, not even to fake basic POSIX permissions, so we can't
  change the permissions at all.

I don't think it's worth to go to great length supporting Cygwin
symlinks on this FS.  They won't be recognized by your Linux
installation as symlinks anyway and we'd have to perform excessively
slow checks just to recognize them.

As a sidenote, the OSS project Ext2Fsd handles symlinks transparently
via standard Windows functions.  With "CYGWIN=winsymlinks:native" you
can generate real ext4 symlinks transparently.  Even the good old Cygwin
symlink works on Cygwin without programmatic intervention, albeit those
won't be recognized as symlinks by Linux of course.  Unfortunately
Ext2Fsd didn't learn to handle ext4 with the 64bit FS option set yet.
64bit is default for quite some time.


Corinna

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Re: symbolic links on Paragon Linux File systems

[Corinna Vinschen]

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Please, do not top-post.


On Dec 17 18:50, Simon Liesenfeld via cygwin wrote:
>  Hi Corinna,
> since you answered your own questionsI can better understand my own
> stupidity.I have created now a hard and a soft link with a native
> linux,then I booted Windows, started the paragon driver,then cygwin 
> programs as well as any dos program perfectly understood the links.

Not in my testing.  I installed the Paragon trial driver and tested
on a filesystem with files and symlinks created by native Linux.  The
symlinks are not understood at all.  From the Windows perspective they
are just plain files with the name of the target file as content.


Corinna

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Corinna Vinschen
Cygwin Maintainer

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Re: symbolic links on Paragon Linux File systems

[Simon Liesenfeld via cygwin]

 Hi Corinnayou are right,I mixed it the symlink with the hard link
the symlink is sl (on file source)

E:\>type sl
source < just the filename as you say>

but the hard link does work (on file source)
E:\>type hl
hallo
erna
otto
hugo

E:\>echo rudi >> source

E:\>type hl
hallo
erna
otto
hugo
rudi

or with cygwin
$pwd/cygdrive/eecho hajo >>source
$ cat hl
hallo
erna
otto
hugo
rudi
hajo



    On Monday, December 17, 2018, 8:22:25 PM GMT+1, Corinna Vinschen <corinna-cygwin@cygwin.com> wrote:  
 
 
Please, do not top-post.


On Dec 17 18:50, Simon Liesenfeld via cygwin wrote:
>  Hi Corinna,
> since you answered your own questionsI can better understand my own
> stupidity.I have created now a hard and a soft link with a native
> linux,then I booted Windows, started the paragon driver,then cygwin 
> programs as well as any dos program perfectly understood the links.

Not in my testing.  I installed the Paragon trial driver and tested
on a filesystem with files and symlinks created by native Linux.  The
symlinks are not understood at all.  From the Windows perspective they
are just plain files with the name of the target file as content.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer  
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