Diagnosing a Linux problem


I was trying to backup my debian server using this s3fs script but apparently I forgot that the script needs fuse in the kernel. Since I just upgraded my kernel to 2.6.30 ,I mistakenly compiled Fuse in the kernel ,It needs to be compiled as a module.

So this provides an excuse to upgrade my kernel again,ok done it . Installing but what is this !!

grub-probe: cannot find a device for /

shucks! Grub has a bug or LVM ..anyway I found a temporary solution in the internet..

To top all of this, debian’s kernel-package has a missing or malfunctioning initramfs hook script which leaves my new kernel without an initrd! Thanks to a backup kernel ,I was able to boot and copy the example initramfs script in /usr/share/kernel-package/examples/ .

Wheeew! that tooked a lot of time to diagnose. . I wonder if stable has this kind of problems .

My Openwrt “LinuxRules!” Dnsmasq setup for LTSP

Here it is ,my dnsmasq.conf :

# filter what we send upstream

# allow /etc/hosts and dhcp lookups via *.lan

# enable dhcp (start,end,netmask,leasetime)

# use /etc/ethers for static hosts; same format as –dhcp-host

# other useful options:
# default route(s): dhcp-option=3,,
# dns server(s): dhcp-option=6,,

#My PXE setup 12-30-06

#new option from http://wiki.ltsp.org/twiki/bin/view/Ltsp/DHCP#dnsmasq

The ones in red are the most important ones coz that will allow you to boot your thinclient via dhcp and nfs.

Big Blue ThinClient with Debian

About a week ago ,I got the IBM Netvista 2200 that I bought from Ebay . I wasn’t expecting it to be that small a thin client . Its just about an inch and a half thick..Anyways, I was planning to setup it up as a diskless client. So I already had a pretty rough idea how a diskless client works.. To sum it up,it gets its kernel from a server and run everything off of that server ..

Well,for a client to boot from the server it must have PXE. Turns out mine doesn’t have it.. so it has to have some other means of booting from a server since it’s a thin client.. to get it to boot one must setup the dhcp server to serve the kernel via NFS since TFTP via PXE doesn’t work ..

I have my Openwrt setup that way ..I’ll post my dnsmasq here next time ..

Azureus and Openwrt

The following problem has been bugging for the past two days . I have been using bittornado for my torrent needs ever since I was in to torrents. Bittornado is curses base and I tried Azureus which is java base for a while but I didn’t really tinker with it that much . Anyways ,I have a router in between my computer and my cable modem . I have OPENWRT White Russian on it. It’s really nice to have a little bit of something in between you and wild net outside ..

My home computer network looks like this :

* Debian Sid on a Pentium 3 500mhz
* Linksys WRT54G ver 2.2 i think
* Openwrt on the Linksys

I was trying Azureus and I notice that It keeps telling me that my Router is not set up right . I always get a either a DHT firewalled or NAT firewalled status on the lower status bar .I went about googling for solutions :

1. I sshd to my router and added the ff line in my /etc/firewall.user: iptables -t nat -A prerouting_rule -i $WAN -p tcp –dport 6880:6990 -j DNAT –to
iptables -A forwarding_rule -i $WAN -p tcp –dport 10000 -d -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p udp –dport 6880:6990 -j DNAT –to
iptables -A forwarding_rule -i $WAN -p udp –dport 10000 -d -j ACCEPT
2. I reloaded the firewall after that by : #/etc/init.d/S45firewall restart
3. however that didn’t work ,so ;I tried changing /etc/config/firewall ,this file is used by NBD’s qos-scripts and according to the info I googled supposedly makes it easy to change the nat behaviour ..
I added this line: forward:dport=6880-69990:

All this suppose to setup my my portforwarding , this supposedly forwards all incoming connections to my routers ports 6880-6990 to my computers port 10000. .
I tried to look at my computers netstat output but all I can see was that my port 10000 is open and when I used shields-up to probe my port 6880-6990 ,it was also open but still no NAT success with Azureus..

I also noticed that the netstat output shows that there are tcp6 and udp6 ports that are open . I didn’t know that I was using anything that has to do with ipv6 .. So I googled my friend google ..hehehehe .. and I came across this forum for redhat users … It suggested there to turn off aliases for ipv6 in /etc/modutils/aliases . That took care of the ipv6 problem when I rebooted no more ipv6 ports opened but i still have no nat for Azureus ..

I finally got a working /etc/firewall.user line that worked .after so many hours of tweaking . I read somewhere that azureus or bittorrent for that matter doesn’t like the usual ports opened coz some isp’s are blocking this ,so I thought about it.. Maybe just change the dport to something else and don’t change the forwarding rule to another port .

So my final rule that got me is this :

iptables -t nat -A prerouting_rule -i $WAN -p tcp –dport 60881 -j DNAT –to
iptables -A forwarding_rule -i $WAN -p tcp -d -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p udp –dport 60881 -j DNAT –to
iptables -A forwarding_rule -i $WAN -p udp -d -j ACCEPT

That dport flag on the prerouting rule is arbitrary .. You can change it to anything . After this I reloaded the firewall and to make sure ,I rebooted the router and also my computer ..
I also change the port settings on Azureus and voila! Magic! My azureus is going green eversince ..

A few pointers ,give it a little while if at startup its yellow .. it takes a while for it to change ..Also,there are some torrents out there that is bad ,meaning ,there is no seeds and tracker site is down ,So if you run into this then it’s not really you thats the problem . Also, I don’t have to say this but if you’re torrenting you must be prepared to give,i mean don’t try to be a leech.. or you’ll get what’s coming to you ..

I hope this helps all those Azureus users out there. Coz ,this has got me some lost hours of sleep!