Hello, in the beginning I had just one simple question :) ... Is there any way to start RAIDs in readonly mode while autodetection on system boot? I was thinking about some 2-stage boot mimic that first enables all RAIDs readonly (while autodetection for example) and then in a second stage sets them to readwrite (in a early init script for example). Such a mimic could provide a chance to system administrators for intervention before automatic resync or such things would take place (by booting up in emergency mode for example). Since I found no solution to tell the autodetection to start up RAIDs in readonly mode, I was thinking about kicking autodetection at all and starting up RAIDs via mdadm or something like that. However, when looking at man mdadm it seems to me that it is impossible there too, to start RAIDs in readonly mode (since --readonly and --readwrite are defined in Misc mode only, while I would need them in Assemble mode, wouldn't I?). So my second question came up :) ... Is there any way to start RAIDs in readonly mode at all? And then while looking at --readonly and --readwrite semantics, some more questions came up :) ... I was trying in emergency mode with two RAID1: md0 and md4. md0: initially readwrite mounted / ro md4: initially readwrite not mounted I'm running 2.4.27 built from Debian's kernel-source-2.4.27. I'm booting with ro in kernel commandline, so root device is mounted readonly initially. # mdadm --readonly /dev/md0 failed to set readonly: EBUSY This is somehow understandable. However, it would be nice to have a way to force it. Furthermore, since the device is (should be?) opened readonly, it should be possible to set it readonly, too. # mdadm --readwrite /dev/md0 failed to set writable: EBUSY Huh, why does that fail? It *is* writable already! # mdadm --readonly /dev/md4 Works. Of course. # mount -o ro /dev/md4 /usr # mdadm --readwrite /dev/md4 Works. Why does it work? If setting an already readwrite device to readwrite fails, *this* one should fail more than ever! # mdadm --readonly /dev/md4 failed to set readonly: EBUSY Expected. However, since this device *must* be opened readonly (since it *was* readonly at mount time), it should definitely be possible to set it back to readonly. Well, the whole readonly/readwrite semantics seem somehow inconsistent to me. Setting a mounted and already readwrite device to readwrite fails, while setting a mounted but readonly device to readwrite works. And a last question came up then, too: blockdev --setro /dev/md0 md: blockdev(pid 3446) used obsolete MD ioctl, upgrade your software to use new ictls. BLKROSET: Invalid argument Is there any objective, why md does not support the standard block device readonly/readwrite ioctls? regards Mario -- Independence Day: Fortunately, the alien computer operating system works just fine with the laptop. This proves an important point which Apple enthusiasts have known for years. While the evil empire of Microsoft may dominate the computers of Earth people, more advanced life forms clearly prefer Mac's. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
