copies bytes from the input file ( if) to the output file ( of), and it does not care that the output file is actually a device, because "everything is a file".Now that we know where it is, we just need to replace those bytes with our file: $ sudo dd if=script.py of=/dev/sdc conv=notrunc bs=1 seek=2573588480 count=202
#UBUNTU IMAGE EDITOR HOW TO#
See INSTALL for how to Īlternatively, this can also be done with grep, which is a lot faster, but then you need to specify it from the beginning: $ sudo grep -oba 'This is. Find some string that is (probably) unique to info.txt, for example This is the official distribution CD of X., and search for it on the disk: $ sudo strings -a -t d /dev/sdc | grep 'CD of X.'Ģ573588480 This is the official distribution CD of X. We are root, though, so let's show 'em what that means! We need to figure out where info.txt is on the filesystem. We can't just overwrite info.txt on the mountpoint, it will complain that it's a read-only filesystem. After mounting it at /mnt, I found a suitable file at /mnt/info.txt. The size of the script is 202 bytes, so our first step is to find a file larger than 202 bytes, so we can overwrite it. The script is at script.py and my target (a USB stick) is at /dev/sdc. In my case, I wanted to store a script in a live boot so I don't have to retype it every time. This actually requires only two commands, but be careful: a typo can destroy the target filesystem completely, or even overwrite the source file. Our desired file must be smaller than the existing (target) file, and trailing whitespace (or garbage) must be acceptable. In summary, we will replace an existing file in the isofs filesystem with our desired file.
#UBUNTU IMAGE EDITOR ISO#
The common answer to this is to unpack the iso file, modify it, and pack it again.
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