Re: [gentoo-user] Strange partition on USB stick
Am 04.10.11 00:15, Mick wrote: I can't recall if I asked this before, but I am looking at a partition on a USB stick which seems to have a FAT16 fs on it and in parted says: == Model: Crucial Gizmo! overdrive (scsi) Disk /dev/sdb: 1023MB Sector size (logical/physical): 512B/512B Partition Table: loop Number Start End SizeFile system Flags 1 0.00B 1023MB 1023MB fat16 == What does Partition Table: loop mean? http://www.mail-archive.com/parted-devel@lists.alioth.debian.org/msg02423.html
Re: [gentoo-user] Strange partition on USB stick
On Tue, 4 Oct 2011 00:27:50 -0500 Paul Hartman paul.hartman+gen...@gmail.com wrote: On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that. I have a 4G Sandisk that does that too. It does everything a regular USB stick does except a) create a proper partition table and b) be booted from -- Alan McKinnnon alan.mckin...@gmail.com
Re: [gentoo-user] Strange partition on USB stick
On Tuesday 04 Oct 2011 06:27:50 Paul Hartman wrote: On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that. If there isn't a partition table, then why fdisk sees /dev/sdb1-4 with somewhat strange ID types? -- Regards, Mick signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Strange partition on USB stick
On Tuesday 04 Oct 2011 07:53:47 Alan McKinnon wrote: On Tue, 4 Oct 2011 00:27:50 -0500 Paul Hartman paul.hartman+gen...@gmail.com wrote: On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that. I have a 4G Sandisk that does that too. It does everything a regular USB stick does except a) create a proper partition table and b) be booted from I guess what I'm asking is: If there isn't a partition table, then why fdisk sees /dev/sdb1-4 with somewhat strange ID types? What is it that it interprets as 4 partitions? -- Regards, Mick signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Strange partition on USB stick
On Tue, Oct 4, 2011 at 1:58 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 06:27:50 Paul Hartman wrote: On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that. If there isn't a partition table, then why fdisk sees /dev/sdb1-4 with somewhat strange ID types? It's misinterpreting the data that happens to be there because it makes the assumption that it's a partition table even though it's not. You can create a real partition table on that device and reformat, if you want. (Note that some flash-based devices suffer degraded performance if you repartition or reformat them because they come with specially-aligned FAT tables from the factory)
Re: [gentoo-user] Strange partition on USB stick
On Tuesday 04 Oct 2011 17:18:18 Paul Hartman wrote: On Tue, Oct 4, 2011 at 1:58 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 06:27:50 Paul Hartman wrote: On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that. If there isn't a partition table, then why fdisk sees /dev/sdb1-4 with somewhat strange ID types? It's misinterpreting the data that happens to be there because it makes the assumption that it's a partition table even though it's not. You can create a real partition table on that device and reformat, if you want. (Note that some flash-based devices suffer degraded performance if you repartition or reformat them because they come with specially-aligned FAT tables from the factory) Interesting! I didn't know that. I have repartitioned USB sticks in the past, but did not notice any change in performance - to be honest I didn't measure it. I assume then that if I were to re-partition for any reason I would need to stick to exactly the same start finish shown by parted. Re-formatting it ought to be OK though, as long as the fat16 shown by parted is correct. -- Regards, Mick signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Strange partition on USB stick
On Tue, Oct 4, 2011 at 1:39 PM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 17:18:18 Paul Hartman wrote: You can create a real partition table on that device and reformat, if you want. (Note that some flash-based devices suffer degraded performance if you repartition or reformat them because they come with specially-aligned FAT tables from the factory) Interesting! I didn't know that. I have repartitioned USB sticks in the past, but did not notice any change in performance - to be honest I didn't measure it. I assume then that if I were to re-partition for any reason I would need to stick to exactly the same start finish shown by parted. Re-formatting it ought to be OK though, as long as the fat16 shown by parted is correct. I think filesystems other than FAT are aligned well already, assuming your partitions are aligned, but with FAT there are some hoops you must jump through. There is a tool called flashbench that can test your drive (destructively!) and figure out the most optimal block sizes. Here's a great article about it and optimizing USB flash drives in general: https://lwn.net/Articles/428584/ And here is a forum thread about figuring out the FAT alignment: http://www.patriotmemory.com/forums/showthread.php?3696 The SD council makes a tool for MS Windows that optimally formats and securely erases SD cards. Might be interesting to compare the results of its format to a standard fdisk and mkfs.vfat in linux. One thing I'm going to do next time I get a new SD card or flash drive is take a snapshot of the boot sector/partition tables/FAT tables so if I ever want to reformat it to FAT, I can restore the -- presumably optimal -- factory layout.
Re: [gentoo-user] Strange partition on USB stick
On Tuesday 04 Oct 2011 20:36:06 Paul Hartman wrote: On Tue, Oct 4, 2011 at 1:39 PM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 17:18:18 Paul Hartman wrote: You can create a real partition table on that device and reformat, if you want. (Note that some flash-based devices suffer degraded performance if you repartition or reformat them because they come with specially-aligned FAT tables from the factory) Interesting! I didn't know that. I have repartitioned USB sticks in the past, but did not notice any change in performance - to be honest I didn't measure it. I assume then that if I were to re-partition for any reason I would need to stick to exactly the same start finish shown by parted. Re-formatting it ought to be OK though, as long as the fat16 shown by parted is correct. I think filesystems other than FAT are aligned well already, assuming your partitions are aligned, but with FAT there are some hoops you must jump through. There is a tool called flashbench that can test your drive (destructively!) and figure out the most optimal block sizes. Here's a great article about it and optimizing USB flash drives in general: https://lwn.net/Articles/428584/ And here is a forum thread about figuring out the FAT alignment: http://www.patriotmemory.com/forums/showthread.php?3696 The SD council makes a tool for MS Windows that optimally formats and securely erases SD cards. Might be interesting to compare the results of its format to a standard fdisk and mkfs.vfat in linux. One thing I'm going to do next time I get a new SD card or flash drive is take a snapshot of the boot sector/partition tables/FAT tables so if I ever want to reformat it to FAT, I can restore the -- presumably optimal -- factory layout. Excellent find! I've got some studying to do. Thanks for sharing. :-) -- Regards, Mick signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Strange partition on USB stick
If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage.
Re: [gentoo-user] Strange partition on USB stick
On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. -- Regards, Mick signature.asc Description: This is a digitally signed message part.
Re: [gentoo-user] Strange partition on USB stick
On Tue, Oct 4, 2011 at 12:18 AM, Mick michaelkintz...@gmail.com wrote: On Tuesday 04 Oct 2011 04:39:45 Adam Carter wrote: If the data is important, I'd use ddrescue to create an image of the drive, then run testdisk over that image to see if it can untangle the partition table mess. Both are in portage. Well, that's the thing: I'm not sure that there is a mess. At least not as far as parted is concerned, which can read the partition table properly. I suspect that fdisk (unlike parted) is not capable of reading the device correctly. I forgot to say that when mounted the USB stick shows not partitions (i.e. there is no sdb1, sdb2, etc.) To access the fs I must do something like: pmount /dev/sdb and then all is lists under /media/sdb. It is like a big floppy. I think that's your answer. The partition table looks funny because it isn't one. :) It is somewhat common. I've had some myself that are like that.
