On Jul 25, 2019, at 10:24 PM, gwes <[email protected]> wrote: > > > On 7/24/19 10:19 PM, Zhi-Qiang Lei wrote: >> Hi, I’m trying to encrypt a DVD-RAM before putting some files onto it on my >> OpenBSD 6.5 desktop. But neither dd nor disklabel seems able to work on the >> drive. Did I miss something? >> >> $ dmesg | grep cd >> cd0 at scsibus3 targ 1 lun 0: <HL-DT-ST, BD-RE BU40N, FR07> ATAPI 5/cdrom >> removable serial.13fd3940302020202020 >> cd0 at scsibus3 targ 1 lun 0: <HL-DT-ST, BD-RE BU40N, FR07> ATAPI 5/cdrom >> removable serial.13fd3940302020202020 >> >> $ doas dd if=/dev/urandom of=/dev/rcd0c bs=1k >> dd: /dev/rcd0c: Invalid argument >> 1+0 records in >> 0+0 records out >> 0 bytes transferred in 0.000 secs (0 bytes/sec) >> >> $ doas disklabel -E cd0 >> cd0> a >> partition: [a] >> offset: [0] >> size: [2236704] >> FS type: [4.2BSD] >> cd0> w >> cd0> p >> OpenBSD area: 0-2236704; size: 2236704; free: 0 >> # size offset fstype [fsize bsize cpg] >> a: 2236704 0 4.2BSD 2048 16384 1 >> c: 2236704 0 unused >> cd0> q >> No label changes. >> >> The same drive can be formatted and used on Mac OS X. >> >> Thanks and best regards, >> Siegfried >> > Did you try 2K blocks? The low level of CDROM only works that way. >
Blocks larger than or equal to 2k get a "dd: /dev/rcd0c: short write on character device”. Regarding to cd(4) I thought the device is readonly, so dd(1) and disklabel(8) cannot write on it, but fdisk(8) works fine. $ doas dd if=/dev/urandom of=/dev/rcd0c bs=2k dd: /dev/rcd0c: short write on character device dd: /dev/rcd0c: Invalid argument 1+0 records in 0+1 records out 512 bytes transferred in 0.008 secs (57960 bytes/sec) $ doas dd if=/dev/urandom of=/dev/rcd0c bs=512 dd: /dev/rcd0c: Invalid argument 1+0 records in 0+0 records out 0 bytes transferred in 0.000 secs (0 bytes/sec)
