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etdump – Dump El Torito boot catalog information from ISO images

SYNOPSIS DESCRIPTION EXAMPLES HISTORY

etdump [-f format] [-o file] file ...

This program reads El Torito boot catalog information from an ISO image and outputs it in various formats. It can be used to check the catalog in an image or to output catalog data in a format that can be used by other tools such as shell scripts.

Supported options are:

-f format --format format
	Select the output format. Supported output formats are:
text	Human-readable text (default)
shell	Each boot entry is emitted as a string suitable for passing to a sh-compatible eval command. The variables emitted are:

et_platform
	The platform ID from the section header. Set to 'default' for the initial (default) entry.
et_system	The system ID from the boot entry.
et_lba	The starting LBA (2048-byte blocks) of the boot image.
et_sectors	The number of sectors (512-byte sectors) that comprise the boot image.

-o file --output file
	Write output to file. If '-' is specified then standard out is used.

To see what entries are in a given boot catalog run etdump passing the filename of the image as an argument like so:

% etdump bootonly.iso
Image in bootonly.iso
Default entry
        System i386
        Start LBA 420 (0x1a4), sector count 4 (0x4)
        Media type: no emulation

Section header: efi, final
        Section entry
                System i386
                Start LBA 20 (0x14), sector count 1600 (0x640)
                Media type: no emulation

To use the output in a shell script a for loop can be used to iterate over the entries returned using eval:

for entry in `etdump --format shell bootonly.iso`; do
        eval $entry
        echo $et_platform $et_system $et_lba $et_sectors
done

The etdump utility first appeared in FreeBSD 11.2