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I have a 1GB USB flash drive which I wanted to use as an installation medium for Linux distros. My first experiment was to be installing Arch on an old laptop (old enough that if I really messed it up, it wouldn't matter). I downloaded the ISO image, and put the USB into the port; it mounted automatically. Following the instructions on Arch's installation how-to page, I ran dd if archlinux-XXXX.iso of /dev/sdg1. I then could not see any files on the USB (whether using ls or nautilus). I umounted it, then plugged it back in, and it had some files on it. I'm afraid I can't remember exactly what they were, but I'm pretty sure I saw a directory named /boot.

I then plugged it into the laptop, which would not boot from the flash drive. I plugged the USB back into my main computer, only to be told:

Unable to mount 168 MB Filesystem
Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sdg1,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try dmesg | tail or so

That command, dmesg | tail, gives the following: [338915.672127] UDF-fs: No anchor found [338915.672133] UDF-fs: No partition found (1) [338955.452708] UDF-fs: No anchor found [338955.452714] UDF-fs: Rescanning with blocksize 2048 [338955.479829] UDF-fs: No anchor found [338955.479834] UDF-fs: No partition found (1) [338955.527366] UDF-fs: No anchor found [338955.527373] UDF-fs: Rescanning with blocksize 2048 [338955.555208] UDF-fs: No anchor found [338955.555213] UDF-fs: No partition found (1)

So I'm curious about what has happened here. Did I do something wrong somewhere? Why is the error message referring to a 168 MB device, when it's supposed to be 1 GB? Also, is there any way to salvage the flash drive, or is it toast?

Edit: Information from fdisk /dev/sdg Command (m for help): p [print the partition table]

Disk /dev/sdg: 1021 MB, 1021125120 bytes
64 heads, 32 sectors/track, 973 cylinders, total 1994385 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xe797d5bb

   Device Boot      Start         End      Blocks   Id  System
/dev/sdg1   *           0      327679      163840   17  Hidden HPFS/NTFS
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up vote 1 down vote accepted

If you were working from Official Arch Linux Install Guide, note that it says:

Make sure to use /dev/sdX and not /dev/sdX1

Assuming you did dd to /dev/sdg1 (as opposed to mistyping the command in your question), you've copied the ISO image into a partition on the flash drive. The partition is likely too small to hold the ISO, and the boot sector of /dev/sdg was untouched.

Probably the best thing to do is re-dd the image, using the correct target. Once that's done, fdisk will probably say you don't have a partition table. Note that in your fdisk output, the total device size is correct, 1021 MB. It's hard to say why the drive might have been formatted with a 168 MB partition.

It is possible to put the ISO in a partition, as long as the partition is big enough, but that's less likely to be bootable.

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Thanks, Andy. In my bash history i had both ...of=/dev/sdg and ...of=-/dev/sdg1. Apparently for some reason I thought the first one didn't work. I reran dd just now, put it in the laptop, and the Arch installer booted just fine. Mea culpa. –  Wolf Apr 25 '11 at 19:36
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