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Old 9th March 2018
acampbell acampbell is offline
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Default usb flash drive insists on being read-only

I have a 2GB usb flash drive which contains some old Debian files that I want to delete.

I've tried mounting it with "-o rw" and also tried "mount -u -o rw" when it's mounted but it remains obstinately read-only. Is there any way to fix this or should I ditch the drive?
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Old 9th March 2018
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jggimi jggimi is offline
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What is the filesystem?
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Old 9th March 2018
acampbell acampbell is offline
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It's cd9660, which seems odd.
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Old 9th March 2018
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That *is* a read-only filesystem. You can back up the contents, reformat into a useable filesystem, and reload.
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Old 9th March 2018
acampbell acampbell is offline
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The contents are unimportant. I'd thought about reformatting but I don't know how to go about doing that in OBSD. Would I use newfs after first running disklabel?
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Old 9th March 2018
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For a drive that might be inserted into multiple OSes, I recommend you start with an MBR. You can use fdisk(8) to create an MBR. The initialized (or reinitialized) default configuration is of a single OpenBSD MBR partition spanning the drive. The fdisk(8) program has an editor which can revise these, or make GPT partitions instead of MBRs. However, some knowledge of how MBR/GPT partitions function is needed to effectively make changes.

To create a default, initial MBR, you can use # fdisk -iy <device>. See the man page for details.

As you noted, you can create OpenBSD disklabel partitions with disklabel(8) and its editor.

Formatting of FFS partitions in OpenBSD is performed with newfs(8).
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Old 9th March 2018
acampbell acampbell is offline
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Many thanks, Iggimi; very useful info, as always.
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Old 9th March 2018
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You're welcome. For clarity, what this creates is an OpenBSD-only removable device. The MBR will keep all other OSes from scribbling on it unless you tell them to reformat. They will recognize the MBR, and the one entry in the partition table will inform the OS that the drive is reserved for something they know nothing about.

If you want a storage device that can be used with other OSes, then the MBR becomes the tool to define a filesystem (such as FAT) that can be shared among the OSes. An OpenBSD disklabel is not actually needed, because when there is no on-disk disklabel, OpenBSD will read the MBR partition table and create a virtual disklabel, assigning disklabel partitions to MBR partitions that it recognizes, starting with partition "i".

(If you have an MBR *and* a disklabel, the two must be manually kept in sync, as OpenBSD will not scan for foreign filesystems in the MBR partition table, and will use the disklabel instead.)

Last edited by jggimi; 9th March 2018 at 09:16 PM. Reason: edit: added the last paragraph
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