Re: screen in single user mode - "cannot open /dev/console"

[Malte Skoruppa]

Usually runlevel 1 is the "single user mode" you spoke of (or whatever 
one likes to call it), and runlevel 3 is the typical mode with X (it 
depends on your distro, though).

Anyway, I'd try to boot in runlevel 1, and from there, manually start 
every service that would normally automatically be started in the next 
runlevel, one by one. Then after each new started service, try out if 
screen works in the way you expect it to. That way, you can find out 
which service(s) you need to start so as to achieve the desired behavior.

Then you could define a new "own" runlevel (see /etc/inittab & co.) with 
exactly those services from runlevel 1 plus the other ones you need, 
which you could use as a default runlevel (or at least, have a grub 
entry for it so you can directly start it), thus avoiding all 
unnecessary services and minimizing CPU/memory usage.

Defining your own runlevel shouldn't be very difficult. Many distros 
have nice tools that make runlevel management pretty easy :-)

Cheers

Malte

> Thanks to all for responding and sorry I couldn't reply earlier.
>
> I am using Ubuntu Linux (Gutsy Gibbon):
>
> $ uname -a
> Linux loki 2.6.22-14-generic #1 SMP Tue Feb 12 07:42:25 UTC 2008 i686 
> GNU/Linux
>
> By "single user mode" I talk of, I mean "single" parameter being 
> passed by Grub bootloader during startup:
>
> kernel        /vmlinuz-2.6.22-14-generic 
> root=UUID=7bb7e9b4-7134-430d-b2bb-cd33c45d0acd ro single
> initrd          /initrd.img-2.6.22-14-generic
>
> I am able to also reach this mode by doing "init 1". I understand that 
> this is supposed to be a spartan recovery mode or for situations where 
> you don't want multiple users.
>
> But in context of my home setup, I wanted to use this to avoid 
> starting up too many services/X/Gnome etc since all I want to do is 
> run some long-running command line programs (for which screen is more 
> than adequate and in fact, perfect). My intention is to use least 
> amount of CPU/memory.
>
> I have noticed that even in this "single" mode, there are services 
> like ntp running and the network interface is already configured so I 
> am able to access internet. So it is not that Nothing is running.
>
> > If you want a textual login then start up normally, and choose 
> "Other..." at the login window prompt and enter
> > ">console" (without quotes). If you do not see "Other..." then hold 
> option and press down, then while still
> > holding option press return. This will take you to the "Other..." 
> pane where you can enter ">console".
>
>
> I don't see these choices when I go into the "Single" user mode or 
> when I start normally and get to GDM (Gnome Display Manager). So not 
> sure how to enable this. As I said, I don't want to run X etc.
>
> Hope this information is of help to you for suggesting a/the solution 
> for me :)
>
> Regards,
> Soumen