installation error: tar: can't remove old file ./var/run: Is

[tsuranim]

I am trying to install archlinux, but get the following error after "./oxnas-install.sh" :

# Verifying MD5
# Extracting
tar: can't remove old file ./var/run: Is a directory
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Extraction FAILED or WRONG rootfs
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!



The only thing I can think of is that before trying archlinux I tried optware, and installing lighttdp according to this guide:
http://www.nslu2-linux.org/wiki/Optware/LLMP

There it states:
1. Install Lighttpd and PHP after making the root file system accessible and creating /var/run:
Type "mount -o rw,remount /"
Type "mv /var /varold". If you stop using optware, you can restore the old var with "mv /varold /var"
Type "mkdir /opt/var". You might not need this if /opt/var already exists.
Type "mkdir /opt/var/run"
Type "ln -s /opt/var /var"
Type "ipkg install lighttpd php fcgi php-fcgi php-pear mysql phpmyadmin"

I did the "mv /varold /var", but maybe the "ln -s /opt/var /var" is causing the problem?

Could some-one give me advise what to do?

[WarheadsSE]

You must have missed a step. There shouldn't have been a var/run under /tmp/usb.

[tsuranim]

Thanks, after I had a new try it installed without an error. Thanks.