Hello!

I have been writing a small script today and I've made a small mistake, that resulted in calling following command:
chmod 644 /
and now I have a big problem... I cannot run anything on my hdd...
I have rebooted from the liveCD and wanted to do chroot, to investigate what had happened, but the following error appears:
chroot: cannot execute /bin/sh: Permission denied

Is there any way to change access rights to the main node of a disk, when it is not mounted as /? or will I have to do format+reinstall? :/

Regards,
Dauron

Try booting with a Live CD, create a mount point (mkdir /omg), mount your partition there (mount /dev/hdx /omg) and then correct the permissions (chmod 755 /omg).
Substitute /dev/hdx with your root partition.

Then try the chroot thing. If it works, try booting as usual.

I've already tried it, it doesn't work
When I mount the partition, all the rights look ok... maybe it is sth. other than the rights of /... but what else can give these 'no permissions'

do what uselpa said, only do chmod 755 /omg/bin/*

As I said, all the rights in the directories, subdirectories and files are ok (at least when the partition is mounted as the subdirectory of /). The problem appears when it is being mounted as /

Solved!
chmod 755 /omg/lib/*
I'm so happy, that I don't have to reinstall the system

Without wishing to sound like a smartarse, this is one of those things which justify the advice "don't use root unless you absolutely have to!" Of course, it may have been unavoidable in this case.