Syslinux , what does '--' do?

Question

What does the '--' do in a normal syslinux config ? I used to see "quiet" after that , but don't know why.

Here's an example from Ubuntu 12.04:

label install
    menu label ^Install
    menu default
    kernel ubuntu-installer/amd64/linux
    append vga=788 initrd=ubuntu-installer/amd64/initrd.gz -- quiet

SamK · Answer 1 · 2013-09-07T13:07:46.607

14

Anything that is passed after the '--' are appended to the default options for the installed system. Everything before the '--' is only used by the installer itself.

Source: http://www.syslinux.org/archives/2009-December/013978.html

When the installation is finished you can find the options in the /etc/default/grub file at the line starting with GRUB_CMDLINE_LINUX_DEFAULT. If you edit this line you wille have to type update-grub so the content of this line is installed in the boot loader (used when launching the Linux kernel).

edited Sep 07 '13 at 13:07

answered Sep 06 '13 at 14:21

SamK

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+1 Though not nearly as verbose, this is the actual answer to the question being asked. – krowe Sep 06 '13 at 15:00
I added a few more infos. This answer now seems fine to me. – SamK Sep 07 '13 at 14:24

score -2 · Accepted Answer · answered May 02 '12 at 14:22

-2

Many commandline tools take arguments. There are one-letter, short, arguments and ... long arguments. They change the default behaviour of such a tool.

Short arguments are prefixed with a single dash - Long arguments are prefixed with a double dash --

Short arguments can be combined into ls -l -t -r is the same as ls -ltr. Long arguments need to be distinguished from combined singles, and to do that, a long argument is prefixed with a double dash ls -l -t --reverse or ls -lt --reverse

Long arguments are easier to remember, short ones faster to type.

Most commands have a manual page which explains these arguments in detail. Eg. man ls for the manual page of the ls command which I used in my examples above.

answered May 02 '12 at 14:22

jippie

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I believe the original question is about the exact sequence `--` in a *configuration* file, not the command line. GNU `getopt(1)` and `getopt(3)` use `--` to signal the end of options. Everything after it is interpreted as an argument. E.g. `grep -- -E file` looks for the string `-E` in `file` (even though `-E` is a `grep` option). This could be what's happening here if syslinux (ab)uses `getopt(3)` to parse its configuration files. (or if it simulates the behaviour) – Alexios May 02 '12 at 15:28
@Alexios maybe you should put that as an answer – daisy May 10 '12 at 05:27
I would, but it's not really an answer. I know the conventional semantics of `--` but I can't answer the question *in spirit* because I don't know what the heck it's doing in a SysLinux `append` line. :) – Alexios May 10 '12 at 09:23

Syslinux , what does '--' do?

2 Answers2