Linux Neophyte Troubleshooting (by Jarred)

I have to give Chris credit: he knows a lot about Linux. In fact, I'm pretty sure he's forgotten more about the subject than I have yet learned! However, being "new" (relatively) to Linux allows me to provide some insight that he may have glossed over. If you're an experienced Linux user, nothing I say here is likely to help out, but for the rest of you I thought before posting this article I'd take a stab at setting up my own proxy server. The "simple" process ended up taking a couple days of on-and-off troubleshooting to get everything working properly. What follows is a brief summary of the things I learned/experienced during my Linux proxy crash course.

First, let's start with the hardware. I had a mini-ITX motherboard and parts available, which would have been perfect! Sadly, the board only has a single network adapter and an x16 PCI-E slot, so I looked elsewhere. I ended up piecing together a system from spare parts.

Jarred's Test System
Component Description
Processor Intel Core 2 Quad Q6600
(2.40GHz, 65nm, 2x4MB cache, quad-core, 1066FSB, 105W)
Memory 2x2048MB DDR2-800 RAM
Motherboard ASRock Conroe1333-eSATA2
Hard Drives 300GB Maxtor SATA
Video Card NVIDIA GeForce 7600GT
Operating Systems Arch Linux (64-bit)
Network Cards Onboard NVIDIA Gigabit (NForce)
PCI TRENDnet Gigabit (Realtek 8169)

Obviously, my spare hardware is a bit more potent than what Chris had lying around, and frankly it's complete overkill for this sort of box. On the bright side, it runs 64-bit Linux quite well, and the NVIDIA GPU makes it gaming capable (if you're not too demanding). Getting Arch installed was the easy part, though; configuring things properly took quite a bit more effort.

I followed the directions and… nothing worked. Ugh. Now, I have to put a disclaimer here: I initially used an old Compaq PCI NIC as my secondary network adapter… and I discovered it was non-functional after a while spent troubleshooting. Or at least, it didn't work with Linux and caused the PC to lock up when I tried to load the driver. Good times! So make sure your hardware works properly in advance and you'll save yourself a headache or two. I picked up the TRENDnet Gigabit NIC at a local shop for just $20 and it installed without a hitch.

Old hardware isn't a problem with Linux; broken on the other hand…

As far as configuring Linux, the wikis Chris linked were generally helpful, though they're more detailed than most people will want/need. The "Arch Way" essentially boils down to giving you a fishing pole and some bait and trying to teach you to fish rather than providing you with a nice salmon dinner. Arch has benefits, and you will learn something about Linux (whether you want to or not), but if you're a newbie plan on spending a fair amount of time reading wikis and searching for solutions as you come to grips with the OS.

After Arch was running and I discovered my Compaq NIC was dead, installing the second NIC required a bit of unexpected work. Since it wasn't present during the OS install, the drivers weren't loaded by default. Using lspci, I was able to find my new NIC, determined it was a Realtek 8169 chipset, and a short Google later I found the necessary driver: modprobe r8169. After spending some time reading about ifconfig and trying a few settings, I got the NIC installed and (apparently) functional, so now it was time to get squid and shorewall configured. (Note that this would have likely been unnecessary had the NIC been present during the Arch install.)

While Chris likes the 10.4.20.x network, I prefer the customary 192.168.x.x. Chris listed a global DNS name server of, which will work fine (a name server from CiberLynx), but I put in the name servers from my ISP (Comcast). I grabbed this information from the /etc/resolv.conf file, placed there by DHCP from the cable modem. I also wanted to use DHCP as much as possible. The result is that I have my onboard NIC plugged into my cable modem, and the TRENDnet NIC connected to my wireless router. I set a static IP of for the TRENDnet NIC, with DHCP providing IPs from through Really, though, I only need one for the wireless router, which then provides its own DHCP for a different subnet: 192.168.10.x. The good thing about this setup is that I never had to touch the configuration on my wireless router, which has been working fine. I just unplugged it from the cable modem and connected it to the Linux box.

Configuring shorewall was simple, but I ended up not getting network access from my Linux box. That was a "works as intended" feature, but I wanted to surf from the Linux box as well. I had to add ACCEPT $FW net tcp www to /etc/shorewall/rules file to get my local networking back, and I added a line to allow FTP to work as well. Getting squid to work wasn't a problem… after figuring out that Chris forgot the "transparent" option for the http_port setting. I created the directory /home/squidcache for the proxy (mkdir /home/squidcache then chmod 777 /home/squidcache), just because I liked having the cache as a root folder. With everything finally configured properly, I did some testing and found everything worked about as expected. Great! I also installed X Windows, the NVIDIA driver, and the KDE desktop manager as per the Beginner's Guide Wiki—useful for editing multiple text files, surfing the web for configuration information, etc. Then I decided to reboot the Linux box to make sure it was truly working without a hitch.

After the reboot, sadly to say I was back to nothing working… locally or via the proxy. Some poking around (using dmesg and ifconfig) eventually led me to the discovery that my NICs had swapped names after the reboot, so the NForce NIC was now eth1 and TRENDnet was eth0. One suggestion I found said that if I put the drivers for my NICs into the MODULES section of rc.conf, I could specify the order. That didn't work, unfortunately, but another option involved creating a file called /etc/udev/rules.d/10-network.rules with two lines to name my NICs. (Get your MAC Address via dmesg|grep [network module] or udevadm info -a -p /sys/class/net/[Device: eth0/eth1/wlan0/etc.].) So I added:

SUBSYSTEM=="net", ATTR{address}=="[NVIDIA NForce MAC]", NAME="eth0"
SUBSYSTEM=="net", ATTR{address}=="[TRENDnet MAC]", NAME="eth1"

At this point, everything worked properly, but I did run into a few minor quirks over the next day or so of testing. One problem was that Futuremark's Peacekeeper benchmark stopped working. Troubleshooting by Chris ended up showing that there was a problem with the header being sent from the Futuremark server (Message: "Invalid chunk header" in /var/log/squid/cache.log). Telling squid not to cache that IP/server didn't help, as the malformed header problem persisted, but we were able to work around the issue by modifying the shorewall rules. Now the redirect line reads: REDIRECT loc 3128 tcp www - !—in other words, redirect all web traffic except for through the proxy.

Wrapping things up, here are the final configuration files that I modified for my particular setup. Providing these files almost certainly goes against the Arch Way, but hopefully having a sample configuration can help a few of you out.

/etc/dhcpd.conf: Put your own ISP name servers in here (from /etc/resolv.conf).
/etc/rc.conf: Specify your network setup, server name, and startup daemons.
/etc/shorewall/rules: The necessary redirect for web traffic to work with your proxy.
/etc/shorewall/shorewall.conf: Only changed the one line to STARTUP_ENABLED=Yes.
/etc/squid/squid.conf: Huge file full of proxy options; here's the short version without comment lines.

Update: It seems my proxy was throttling performance when using "diskd" for the cache directory; changing it to aufs has fixed the situation. With diskd, I experienced intermittent bursts of Ethernet transfer rates, with other transfers limited to <500KB/s. We're not sure why this happened, but you may want to check your network transfer rates with iptraf (pacman -S iptraf, then run it and choose the "S" option to view real-time network transfers).

So what are the benefits to running the proxy cache? If you run multiple machines (I've got more than a dozen at present, with systems constantly arriving and leaving), the proxy cache means things like Windows Updates won't have to go to the web every time and download several hundred megabytes of data. That same benefit is potentially available for other services (i.e. FTP), and in an ideal world I'd be able to cache the various Steam updates. Sadly, Valve doesn't appear to like that, so all of my systems need to go out to the Valve servers to update. Except, you can manually copy your steamapps folder from one system to another and avoid the downloads. But I digress. The squid proxy can also provide a host of other capabilities, from anti-virus support to web filtering and even limiting access to certain times of the day.

The bottom line is that if you have an old system lying around—certainly my quad-core proxy is overkill, and even a Pentium 4 is more than you actually need—you can definitely benefit. A small ITX box or perhaps even an Atom nettop would be perfect for this sort of thing, but most of those lack the requisite dual NICs. You could try a PCIe NIC with mini-ITX, though it's questionable whether the x1 cards will function properly in a mini-ITX board with a single x16 slot intended for graphics use. Barring that, a uATX setup would work fine. Our only recommendation is that you consider the cost of electricity compared with the hardware. Sure, Linux will run fine on "free" old hardware, but a proxy server will generally need to be up and running 24/7, so you don't want to have a box sucking down 100W (or more) if you can avoid it.

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  • dilidolo - Tuesday, May 11, 2010 - link

    I use pfSense as my firewall and wireless AP. Just use an old PC with pci wireless card and you are set, not even a wireless router
  • JarredWalton - Tuesday, May 11, 2010 - link

    You can of course go that route. You could make the Linux box your router and DHCP source. But most people already have a wireless router so connecting to that makes sense to me. I'd have to purchase a wireless PCI card to put in a Linux box, and traditionally wireless cards have far more limited range than routers (due to the single small antenna and sub-optimal location of being behind a large computer).

    But as with all things Linux, there are many ways to set things up. This was a short article to introduce a useful concept that many users likely haven't thought about.
  • leexgx - Tuesday, May 11, 2010 - link

    i was going to question the same thing but then i thought last time i setup IPcop i would of done the same thing disable the DHCP server and use it as an HUB/AP

    main thing i loved with IPcop was the bandwidth throttle i could cap it 5KB under my upload limit i could set utorrent or emule to full upload speeds and i could still play games online lag free (but removed due to lack of supporting uPnP i needed it for MSN remote support and games that Required Upnp {bit lame} at all hope this review used an linux distro with an upnp server on the lan side and i had an look and it did not)
  • ninjaproxy - Monday, May 20, 2013 - link

    With a proxy site you can browse your favorite web sites anonymously and even from behind a firewall with blocked ports. Whether you are on the job, at school, a college university, a public terminal or anywhere else with a web browser.
  • Zok - Tuesday, May 11, 2010 - link

    I've always wanted to tackle something like this, but the power draw has always been the biggest turn off. If average power consumpton hovers around 100W, that's about $105/year for the American average.

    I'd love to ditch my router/AP, but, sadly, I just don't see the benefit of replacing it with something that's significantly more power hungry, unable to act as a dual-band 802.11n AP (last I checked, the drivers weren't out yet for AP mode, if ever), would cost nearly as much as a good dedicated device to outfit with 3-4 additional LAN ports, and is typically physically large and hideous - not to mention the PITA of hours of initial setup and troubleshooting, when you're not a Linux expert.

    In my dreams, I wish there would simply be a beefier all-in-one WRT54G-like device running an Atom, supported dual-band 802.11n radio(s), and SATA, allowing for full-blown Linux in a compact package that would be so win.
  • JarredWalton - Tuesday, May 11, 2010 - link

    Depends on where you live, obviously, though the national average appears to be just over $0.10 per kWh:

    That's why I mention the attractiveness of a Mini-ITX setup, particularly with Atom or similar. Most nettops use a maximum of around 25W, so that would be 1/4 the cost of a typical system, and a nettop is about the same size as a standard router. Too bad they don't have two NICs.
  • Zok - Tuesday, May 11, 2010 - link

    I've explored such a scenario. Unfortunately, at this point, the best it seems I can do is the Mini-ITX router going to the 802.11n AP. Adding another device into the network (upfront cost + power), without removing any others seems like a poor value proposition to me, at least with FiOS speeds.

    Don't get me wrong, I like the idea. I'm just waiting for someone to come along and actually produce a fully-integrated device (x86 CPU, memory, mobo, 4-5 Ethernet ports, Linux-AP supported 802.11n radios, case - without using large expansion cards/slots) that is under $250 and isn't awkwardly large and ugly. Having the 4-5 port switch and (potentially) the radios integrated into the motherboard itself is what I am looking for, although I'd be OK with Mini-PCIe for the radios.
  • taltamir - Tuesday, May 11, 2010 - link

    Don't get me wrong, I like the idea. I'm just waiting for someone to come along and actually produce a fully-integrated device (x86 CPU, memory, mobo, 4-5 Ethernet ports, Linux-AP supported 802.11n radios, case - without using large expansion cards/slots) that is under $250 and isn't awkwardly large and ugly. Having the 4-5 port switch and (potentially) the radios integrated into the motherboard itself is what I am looking for, although I'd be OK with Mini-PCIe for the radios.

    I am pretty much in the same boat.
    at my power rate a 24/7/365 device costs me about 1$ per watt per year.
    so putting a 75 watt old computer there is another 75$ a year...

    I can't wait to ditch my router for a linux based router, but it doesn't seem to be happening.
    Actually, it doesn't even need to be an x86 CPU, any CPU will do. ARM and PowerPC are both supported by linux
  • ChrisRice - Tuesday, May 11, 2010 - link

    There are various power saving techniques you can use to keep the power down as well. If your processor supports speed stepping you can utilizing that as well as powering down actual hardware until use is needed. I wanted to keep the article short so I didn't get into those areas.
  • clarkn0va - Friday, May 14, 2010 - link

    A little over your stated budget, but good value nonetheless. Throw a supported wireless card (try into the spare slot, add your favourite distro and life is good.

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