Date: Mon, 09 Dec 2019 15:51:28 +0000 From: bugzilla-noreply@freebsd.org To: geom@FreeBSD.org Subject: [Bug 242341] GEOM / GEOM_PART: silent discard MBR modification Message-ID: <bug-242341-14739-XZ3ckqIBpU@https.bugs.freebsd.org/bugzilla/> In-Reply-To: <bug-242341-14739@https.bugs.freebsd.org/bugzilla/> References: <bug-242341-14739@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D242341 --- Comment #7 from Andrey V. Elsukov <ae@FreeBSD.org> --- (In reply to Tomasz "CeDeROM" CEDRO from comment #6) And again, You didn't provided any useful info. > 1. dd if=3D/dev/da0 of=3D/dev/da1 bs=3D512 count=3D1 does not copy anythi= ng. Please, use script(1) command if you unable to make a copy from your termin= al. Should be something like this: # dd if=3D/dev/da0 of=3D/dev/da1 count=3D1 1+0 records in 1+0 records out 512 bytes transferred in 0.001958 secs (261495 bytes/sec) You can use hexdump(1) command to check the result of your copy, e.g. # dd if=3D/dev/da1 count=3D1 | hexdump -vC > 2. dd if=3D/dev/zero of=3D/dev/da1 bs=3D512 count=3D1 zeroes the mbr. This looks impossible, if first command doesn't work, this also wont work. > Can you please explain in detail what does it mean exactly "ignores the=20 > partition table"? I guess here is the problem. There is no problem, all described in gpart(8) man page. "Ignores" means th= at GEOM_PART class will not create geom object of type MBR and there will no partitions appears.=20 > If the "partition table is ignored", then why it is silently ignored,=20 > writes to MBR goes to /dev/null, reads from MBR does not update disk > layout, while it is possible to write to the rest of the disk? > Why the whole disk is not locked against writing in a clearly=20 > distinguishable manner? Like error return code from DD and error=20 > messages in DMESG? I don't think that something like this happens in reality :) > So you confirm that the write to MBR was silently discared and the whole > situation is indeed managed by GEOM_PART. This is exactly the problem I=20 > am reporting. Thank you :-) You still misunderstand how all things work. There are different GEOM objec= ts, and when MBR is ignored, GEOM_PART discards nothing, since there is no rela= ted GEOM object. This is why I asked to show the output of `gpart show` and `gp= art list` commands. --=20 You are receiving this mail because: You are the assignee for the bug.=
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