Sanity check - need a second pair of eyes ;-)

Sanity check - need a second pair of eyes ;-)

[Carlos E. R.]

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Hi,

I'm trying to create an XFS image to be written on a Blue Ray disk, 
encrypted. I'm told that DVDs have a sector size of 2 KiB, thus it is 
beter to tell the formatting utility of that, because when creating the 
image file it is on a hard disk where sector size is 512B.

Basic procedure:

truncate -s 50050629632 image_1_50.img
losetup -f image_1_50.img
cryptsetup luksFormat --type luks2 --label blueray50img /dev/loop0
cryptsetup luksOpen /dev/loop0 cr_nombre


So now I have the image file loop mounted on /dev/mapper/cr_nombre, and I 
do (this is the step I ask about):

Telcontar:/home_aux/BLUERAY_OPS # mkfs.xfs -L ANameUnseen -b size=2048 
/dev/mapper/cr_nombre
meta-data=/dev/mapper/cr_nombre  isize=512    agcount=4, agsize=6109184 blks
          =                       sectsz=512   attr=2, projid32bit=1
          =                       crc=1        finobt=1, sparse=0, rmapbt=0
          =                       reflink=0
data     =                       bsize=2048   blocks=24436736, imaxpct=25
          =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=2048   blocks=11932, version=2
          =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
Telcontar:/home_aux/BLUERAY_OPS #


Is that the correct command line to achieve written sectors of 2 KiB?

I ask because I see isize=512 and sectsz=512 and I wonder.


- -- 
Cheers,
        Carlos E. R.
        (from openSUSE 15.0 x86_64 at Telcontar)
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Re: Sanity check - need a second pair of eyes ;-)

[Eric Sandeen]

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> 
> 
> Hi,
> 
> I'm trying to create an XFS image to be written on a Blue Ray disk, encrypted. I'm told that DVDs have a sector size of 2 KiB, thus it is beter to tell the formatting utility of that, because when creating the image file it is on a hard disk where sector size is 512B.
> 
> Basic procedure:
> 
> truncate -s 50050629632 image_1_50.img
> losetup -f image_1_50.img
> cryptsetup luksFormat --type luks2 --label blueray50img /dev/loop0
> cryptsetup luksOpen /dev/loop0 cr_nombre
> 
> 
> So now I have the image file loop mounted on /dev/mapper/cr_nombre, and I do (this is the step I ask about):
> 
> Telcontar:/home_aux/BLUERAY_OPS # mkfs.xfs -L ANameUnseen -b size=2048 /dev/mapper/cr_nombre
                                                             ^^^ block size

> meta-data=/dev/mapper/cr_nombre  isize=512    agcount=4, agsize=6109184 blks
>          =                       sectsz=512   attr=2, projid32bit=1
>          =                       crc=1        finobt=1, sparse=0, rmapbt=0
>          =                       reflink=0
> data     =                       bsize=2048   blocks=24436736, imaxpct=25
                                   ^^^ block size
>          =                       sunit=0      swidth=0 blks
> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
> log      =internal log           bsize=2048   blocks=11932, version=2
>          =                       sectsz=512   sunit=0 blks, lazy-count=1
> realtime =none                   extsz=4096   blocks=0, rtextents=0
> Telcontar:/home_aux/BLUERAY_OPS #
> 
> 
> Is that the correct command line to achieve written sectors of 2 KiB?

If you want to set the sector size, the instructions are in the man page for
mkfs.xfs ;)

       -s sector_size
              This  option  specifies  the  fundamental  sector  size  of  the
              filesystem.  The sector_size is specified either as a  value  in
              bytes  with  size=value  or  as  a base two logarithm value with
              log=value.  The default sector_size is 512  bytes.  The  minimum
              value for sector size is 512; the maximum is 32768 (32 KiB). The
              sector_size must be a power of 2 size and cannot be made  larger
              than the filesystem block size.

-Eric

> I ask because I see isize=512 and sectsz=512 and I wonder.
> 
> 
> -- Cheers,
>        Carlos E. R.
>        (from openSUSE 15.0 x86_64 at Telcontar)
> 


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Re: Sanity check - need a second pair of eyes ;-)

[Carlos E. R.]

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On 24/07/2019 22.21, Eric Sandeen wrote:

...

>> Is that the correct command line to achieve written sectors of 2 KiB?
> 
> If you want to set the sector size, the instructions are in the man page for
> mkfs.xfs ;)
> 
>        -s sector_size
>               This  option  specifies  the  fundamental  sector  size  of  the
>               filesystem.  The sector_size is specified either as a  value  in
>               bytes  with  size=value  or  as  a base two logarithm value with
>               log=value.  The default sector_size is 512  bytes.  The  minimum
>               value for sector size is 512; the maximum is 32768 (32 KiB). The
>               sector_size must be a power of 2 size and cannot be made  larger
>               than the filesystem block size.

Thanks. 

(Yes, I looked at the manual but did not /see/ aka understand what I really needed).

My page is a little bit different:

       -s sector_size_options
              This option specifies the fundamental  sector  size  of
              the filesystem.  The valid sector_size_option is:

                   size=value
                          The  sector  size is specified with a value
                          in bytes.  The default sector_size  is  512
                          bytes. The minimum value for sector size is
                          512; the maximum is  32768  (32  KiB).  The
                          sector_size  must  be a power of 2 size and
                          cannot be made larger than  the  filesystem
                          block size.

                          To  specify any options on the command line
                          in units of sectors, this  option  must  be
                          specified  first so that the sector size is
                          applied consistently to all options.

Thus the final command line was:

# mkfs.xfs -L ANameUnseen -s size=2048 /dev/mapper/cr_nombre
meta-data=/dev/mapper/cr_nombre  isize=512    agcount=4, agsize=3054592 blks
         =                       sectsz=2048  attr=2, projid32bit=1
         =                       crc=1        finobt=1, sparse=0, rmapbt=0
         =                       reflink=0
data     =                       bsize=4096   blocks=12218368, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
log      =internal log           bsize=4096   blocks=5966, version=2
         =                       sectsz=2048  sunit=1 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0


-- 
Cheers / Saludos,

		Carlos E. R.
		(from 15.0 x86_64 at Telcontar)


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Re: Sanity check - need a second pair of eyes ;-)

[Carlos Maiolino]

> 
> Thanks. 
> 
> (Yes, I looked at the manual but did not /see/ aka understand what I really needed).
> 
> My page is a little bit different:
> 
>        -s sector_size_options
>               This option specifies the fundamental  sector  size  of
>               the filesystem.  The valid sector_size_option is:
> 
>                    size=value
>                           The  sector  size is specified with a value
>                           in bytes.  The default sector_size  is  512
>                           bytes. The minimum value for sector size is
>                           512; the maximum is  32768  (32  KiB).  The
>                           sector_size  must  be a power of 2 size and
>                           cannot be made larger than  the  filesystem
>                           block size.
> 
>                           To  specify any options on the command line
>                           in units of sectors, this  option  must  be
>                           specified  first so that the sector size is
>                           applied consistently to all options.

There was an update on the manpage past year which changed this section, the
usage is the same.

> 
> Thus the final command line was:
> 
> # mkfs.xfs -L ANameUnseen -s size=2048 /dev/mapper/cr_nombre

Looks correct.


But I apologize if it's a dumb question, but what do you expect to achieve by
setting the sector size here? You will be essentially writing the fs image file
over the BluRay Filesystem (which IIRC uses UDF), so, the sector size set on
your xfs filesystem image won't matter much, unless I'm missing something, which
is exactly why I'm asking it :)

Cheers

> meta-data=/dev/mapper/cr_nombre  isize=512    agcount=4, agsize=3054592 blks
>          =                       sectsz=2048  attr=2, projid32bit=1
>          =                       crc=1        finobt=1, sparse=0, rmapbt=0
>          =                       reflink=0
> data     =                       bsize=4096   blocks=12218368, imaxpct=25
>          =                       sunit=0      swidth=0 blks
> naming   =version 2              bsize=4096   ascii-ci=0, ftype=1
> log      =internal log           bsize=4096   blocks=5966, version=2
>          =                       sectsz=2048  sunit=1 blks, lazy-count=1
> realtime =none                   extsz=4096   blocks=0, rtextents=0
> 
> 
> -- 
> Cheers / Saludos,
> 
> 		Carlos E. R.
> 		(from 15.0 x86_64 at Telcontar)
> 




-- 
Carlos

Re: Sanity check - need a second pair of eyes ;-) -- DVD mount error

[Carlos E. R.]

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On 25/07/2019 14.11, Carlos Maiolino wrote:

> But I apologize if it's a dumb question, but what do you expect to achieve by
> setting the sector size here? You will be essentially writing the fs image file
> over the BluRay Filesystem (which IIRC uses UDF), so, the sector size set on
> your xfs filesystem image won't matter much, unless I'm missing something, which
> is exactly why I'm asking it :)

Not dumb question - I'm burning directly the XFS image raw to the DVD, as if it were an ISO :-)

But the image is encrypted with LUKS - that's the purpose, to get encrypted DVDs. password protected UDF would be fine, though, but no such thing exists.

I have not used the procedure for years, though. DVD are too small; now I got a blueray writer I'm trying again after a decade.

The basic procedure is this: <https://www.frederickding.com/posts/2017/08/luks-encrypted-dvd-bd-data-disc-guide-273316/>, but my procedure is older than that, I created it myself IIRC.

This is the configuration; file /etc/crypttab contains:

crmm_dvd.l      /dev/dvd.l                                      none    noauto,loop
crmm_dvd.lr     /dev/dvd.lr                                     none    noauto,loop
crmm_dvd.lx     /dev/dvd.lx                                     none    noauto,loop

(tried also without "loop")
/dev/dvd.lx is a symlink to /dev/dvd


/etc/fstab:

/dev/mapper/crmm_dvd.l          /mnt/dvd.crypta.l       auto            ro,noauto,user,lazytime                 0 0
/dev/mapper/crmm_dvd.lr         /mnt/dvd.crypta.lr      reiserfs        ro,noauto,user,lazytime,barrier=flush   0 0
/dev/mapper/crmm_dvd.lx         /mnt/dvd.crypta.lx      xfs             ro,noauto,user,lazytime                 0 0


(I have a script to automate decoding and mount, but this time I'm doing manually to show the steps)


I'm getting a problem on mount, though :


... # cryptsetup luksOpen /dev/dvd crmm_dvd.lx
Enter passphrase for /dev/dvd: 
... # l /dev/mapper/
total 0
drwxr-xr-x  2 root root     120 Jul 25 18:17 ./
drwxr-xr-x 22 root root    7580 Jul 25 18:16 ../
crw-------  1 root root 10, 236 Jul 23 11:41 control
...
lrwxrwxrwx  1 root root       7 Jul 25 18:17 crmm_dvd.lx -> ../dm-2
... # 

... # mount -v /dev/mapper/crmm_dvd.lx /mnt/dvd.crypta.lx
mount: /mnt/dvd.crypta.lx: mount(2) system call failed: Function not implemented.   <=============== HERE ==============
 # 


Possible related to this log entry:

<0.4> 2019-07-25 18:19:19 Telcontar kernel - - - [127181.795181] XFS (dm-2): device supports 2048 byte sectors (not 512)



This worked years ago with plain DVDs. I can mount the dd image out of the dvd into the hard disk, though:

dd if=/dev/dvd of=out.img bs=16M
BLUERAY_OPS # losetup -f out.img
BLUERAY_OPS # losetup -a
/dev/loop1: [2087]:1209048961 (/home_aux/BLUERAY_OPS/out.img)
/dev/loop0: [2087]:1209048958 (/home_aux/BLUERAY_OPS/image_1_50.img)
BLUERAY_OPS # cryptsetup luksOpen /dev/loop1 cr_dvdimage
Enter passphrase for /dev/loop1: 
BLUERAY_OPS # md mnt2
BLUERAY_OPS # mount -v /dev/mapper/cr_dvdimage ./mnt2
mount: /dev/mapper/cr_dvdimage mounted on /home_aux/BLUERAY_OPS/mnt2.
BLUERAY_OPS # 

BLUERAY_OPS # file out.img 
out.img: LUKS encrypted file, ver 2 [, , sha256] UUID: 0f73c10a-b3e0-4b1b-b124-567abef92fa1
Telcontar:/home_aux/BLUERAY_OPS #

BLUERAY_OPS # file -s /dev/mapper/cr_dvdimage
/dev/mapper/cr_dvdimage: symbolic link to ../dm-3
BLUERAY_OPS # file -s /dev/dm-3
/dev/dm-3: SGI XFS filesystem data (blksz 2048, inosz 512, v2 dirs)
BLUERAY_OPS # 

BLUERAY_OPS # file -s /dev/dm-2     # that's the decoded DVD
/dev/dm-2: SGI XFS filesystem data (blksz 2048, inosz 512, v2 dirs)
BLUERAY_OPS 

Telcontar:/home_aux/BLUERAY_OPS # df -h ./mnt2
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/cr_dvdimage   47G   47G  183M 100% /home_aux/BLUERAY_OPS/mnt2
Telcontar:/home_aux/BLUERAY_OPS # 

Telcontar:/home_aux/BLUERAY_OPS # df -H ./mnt2
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/cr_dvdimage   51G   50G  192M 100% /home_aux/BLUERAY_OPS/mnt2
Telcontar:/home_aux/BLUERAY_OPS # 




-- 
Cheers / Saludos,

		Carlos E. R.
		(from 15.0 x86_64 at Telcontar)


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