Sorry, could not display all the contents of "/ on ftp.whatsmykarma.com"

So, I gave this a try instead with the commandline ftp client on this machine, and it worked fine.  This had me scratching my head, but I figured it out eventually.  Basically, the problem is one of passive vs active FTP – look a the Wikipedia page for more information.  As it turned out, the commandline FTP client was defaulting to active mode, which basically means that the server listens on one port, and connects to a port on the client (that is, the client has to have one open and listening) to make the transfer.  This is fine if you’re on a local network, or have a loose environment firewall-wise where the server can talk to the client this way.  However, because this setup is a bit more difficult, passive FTP was introduced – the server listens on one port and then some other random ports.  The client doesn’t have to listen, just connect to the server on port 21, and then get which other port it has to connect to on the server to actually do the transfer.  This is basically an improvement, but it still means we want to listen on more ports than just 21.  For whatever reason Nautilus only seems like passive FTP (which is probably a good thing), and was giving that error because I’d only forwarded port 21 on the server.

Now, the fix for this is simple, but before I give much of my vsftpd.conf file I would like to address a concern that will no doubt be brought up: FTP isn’t that great.  Well, not from a security standpoint, at least.  Normal FTP just sends everything in clear text, and with minimal effort someone who has access to the datastream (eg, the guy in charge of your company’s firewall, or someone on your wireless network) can easily get this information.  Perhaps your FTP login details are used elsewhere, like for logging into to a system account.  (Like, you sit at your workstation and login with those credentials, and someone else getting them means they can read your Email and delete your crap.)  These days there are better options, such as SFTP (basically an FTP-like protocol that tunnels over SSH, and only really needs OpenSSH) that are better for a lot of things.  However, FTP is nice for certain things, like if you have a server that hosts a bunch of big files you want to put up for download.  You can do this with anonymous FTP, with no need for sensitive usernames and passwords.  I’m going to assume that this is kind of why you’re looking into FTP, and that roughly you know what you’re doing.  (Note that it’s also possible to use FTP with SSL, which could be handy in some cases when you really want to use FTP with login info.)

Anyway, here’s what we have to do.  We want to use passive FTP, and configure vsftpd thusly.  To do this we need to forward port 21 to it (of course), but we also need to have it listen on another port to do the transfers.  Traditionally the FTP server would randomly pick a port from a range, but you really only need one.  I chose 2020.  It can be anything, so long as it’s above 1024.  This is because the server will try to bind it as a non-root user.

Now, the other thing the server will do when we tell it we want to go into passive mode is send an address for the client to connect to (with the given port).  In my case, I’m on a dynamic IP, so we would like to give it a hostname to use.  Luckily, vsftpd will allow us to do all this.  So, for a simple, anon-only FTP server that works in passive mode, here is my config:

listen=YES
local_enable=NO
anonymous_enable=YES
write_enable=NO
anon_root=/var/ftp
pasv_enable=YES
#
# Optional directives
#
#anon_max_rate=2048000
xferlog_enable=YES
listen_port=21
pasv_min_port=2020
pasv_max_port=2020
pasv_addr_resolve=YES
pasv_address=ftp.example.com

Change the details or add stuff to suit your setup.  Note that we have a pasv_min and pasv_max port, these can just be the same thing.  pasv_addr_resolv=YES just lets us specify a hostname.  And that’s that, restart vsftpd and enjoy FTP.

There are various homebrew projects like these floating around the Internet, and I hope to contribute something.  By posting about these here, I hope that I remain focused on them .  This should be interesting, and maybe even useful to someone.  I’ll try to give an update here and there as I come up with more of a solid design for both.

First, a little about my setup.  I have two network cards in this machine.  One is the onboard gigabit one, which is my main nic (eth0).  The other is an extra PCI one (eth1) that I have statically configured for cases when I want to do a direct transfer between machines, or troubleshoot (like in this case).  The problem was, eth0 wasn’t coming up, and was instead doing a DHCP timeout (as if it weren’t connected at all).  I checked the cables, all looked good.

I ended up booting into the System Rescue CD (which I recommend having on hand if you do anything with computers) and checking a few things out.  I checked /var/log/messages and found these lines:

Mar 27 15:18:56 fishingcat kernel: [   13.847407] ADDRCONF(NETDEV_UP): eth0: link is not ready
Mar 27 15:18:57 fishingcat dhcpcd[2401]: eth0: waiting for carrier

This had me puzzled, but then I found this:

Mar 27 15:27:12 fishingcat /etc/init.d/udev-mount[7333]: Udev uses a devtmpfs mounted on /dev to manage devices.
Mar 27 15:27:12 fishingcat /etc/init.d/udev-mount[7335]: This means that CONFIG_DEVTMPFS=y is required
Mar 27 15:27:12 fishingcat /etc/init.d/udev-mount[7336]: in the kernel configuration.
Mar 27 15:27:12 fishingcat /etc/init.d/udev-mount[7324]: ERROR: udev-mount failed to start
Mar 27 15:27:12 fishingcat /etc/init.d/udev[7323]: ERROR: cannot start udev as udev-mount would not start

Bingo.  I had remembered from an encounter at work that udev likes to create persistent naming rules for hardware.  This is a new feature, and is generally a good thing: it keeps eth0 as eth0 for the next reboot, same for eth1.  But with udev not starting, no dice.  So, following the error message, I enabled the appropriate kernel option in make menuconfig.  (For me, this was under Device Drivers -> Generic Driver Options -> Maintain a devtmpfs filesystem to mount at /dev.)

I’m not really sure what caused that to become disabled in the first place, but it’s fixed now, so there you go.

This post, however, is not about the berry, but the Raspberry Pi, a tiny embedded Linux system that boasts enough power to be a full-featured desktop.  (If you came upon this post, you’re probably already somewhat familiar.)  There are two models, at $25 and $35.  The more expensive one has two USB ports as well as an Ethernet port.  (The lesser, I believe, only has one USB and no Ethernet.  But, you could get a hub.)  Both have a 700 MHz ARM-based CPU, and 256 MB of RAM.  They are surprisingly capable graphics-wise (check out the link for more details), and they are also low power.  This is what interests me.

I posted before about possibly configuring my Web server to run at least partly on solar power.  On that post, someone commented on the possibility of using the Pi for this.  And so, I have a model B on order – this board uses about 3.5 watts, so that’s a start.  I would use an external USB drive for much of the filesystem, which would bring this up some, but it should still be less than my current setup which consists of a Mini-ITX board (about 1 GHz, with 256 MB RAM and a 120 GB hard drive).

I have a model B on order (should come in May), and my plan is to throw Debian on there and test this out.  My current server does a decent amount, but it doesn’t seem to get overtaxed.  I’d be looking to run Web (Apache; yes I know there are smaller servers that might work, but I’d like to try this), PHP, MySQL, Email (Postfix/Courier), and LDAP (Email backend).  This should be interesting, and if I make careful use of the onboard SD card I think there’s a shot that this could turn out well.

As for power, part of the inefficiencies of my current setup (roughly 30-4o watts at the plug) are due to the power supply.  With a much smaller supply I should be able to bring this down.  As I also mentioned in the other post, I would like to come up with some sort of power sharing solution, where the primary power source for the Pi is solar, with the mains as a fallback and a battery backup in case of a power failure.  The idea would be to keep a normal system battery charged, rather than taxing it by cycling it each night to keep the server running.  Maybe someday I’ll end up with so much solar that the ~10 watts the whole setup should draw will be a drop in the bucket 24 hours a day (10 * 24 = 240 watt-hours/day), but for now I would take this approach.  (Also, a backup battery is good for other things, and I probably won’t care much about my Web server compared to, say, charging the cell phone or pumping out the basement.)

If the Pi isn’t up to this, I’ll probably try it with a media center-type application, and maybe look into a Sheevaplug for the server.  (It has USB also, so I could literally almost drop it in place.)  My server does get its fair share of hits, between this site, the Fever Dreams mirror, and when I host images on message boards like Fark.  But, I think that a small machine should be fine.

• I have projects that I need to look at.
• I am trying to brush up on Unix network programming.
• Qt would also be good to know.
• I was messing with my Web server a little, and due to permissions some images stopped showing up.  This should be fixed now.
• The Raspberry Pi looks like an awesome idea, and at $25 or $35 each I recommend one for learning about Linux, programming, low-power computing, or just plain dicking around.  Also, buying it helps fund a good cause.
• I need to start posting more stuff about music here.
• Snow is nice in the winter (at least I think it is, in moderate amounts), but I’m fine with the current weather as long as the snow is not pushed up to May or June.

Well, if I think of more, you know where to find it.  Until then, enjoy the weather.

Anyway, as you may have seen me post here in the past, I’ve had some interesting issues with my Lenovo G530 laptop.  First, the screen became wobbly and shaky.  Then, it started to flicker.  The first of these was easy to fix, the second very annoying, and almost as easy to fix.  Well, I write now because the dreaded LCD flickering has returned.  Now, it’s been a while since I posted about it last, but in truth the fix lasted for maybe three weeks.  Figuring the cable had come loose, I repeated it, giving me another couple weeks.  Finally, a couple weeks ago I reseated the video cable only to have reliable operation for maybe a few hours before the flashing came back.  It seemed that the work around involved slapping the display repeatedly in certain locations along the sides, which served to jostle the wiring back into place, as well as relieve some of my frustration.  Then last week, after doing this for a while, I got fed up with this.  Here was the result:

Now, you might think that that was a little bit harsh.  But, I disassembled part of the screen and put it back together again.  I figured that somewhere in there something was in a bad position, and just needed to be tweaked a little.  And, it worked!  Since doing this I’ve had no flickering.  You might be wondering what, specifically was the problem.  Well, I still am too – all I did was take it apart and put it back together again, and it seems fine.

Now, given the popularity of previous posts a nice guide is in order.  However, there are a few things to keep in mind before going through this and attempting it yourself:

• After taking pictures, I realized that I probably could have gotten some better ones for illustrative purposes.  So, I recommend that you take a look at Lenovo’s page with take-apart instructions for this unit.  Also, look over the entire graphic carefully before attempting anything, just to get a general idea.
• You need to first follow the instructions for getting at the screen hinges, as well as reseating the video cables.  The first of these is more important.  Use it to get at the hinges; don’t tighten them as we’ll be unscrewing them.  The second is less necessary, but I recommend it to have easier access to the cables, and because you may as well reseat those while you’re tearing this thing apart.
• There are a tone of small screws and such in this.  You probably already know this if you’ve taken it apart before, but it bears restating.  Find a clear, hard surface like a kitchen table to work on this, and keep track of your screws.  It should go without saying that an appropriate screwdriver set is a must (though you’re probably good if you’ve done this before).
• Be careful when removing the screen bevel (after unscrewing the screws under the little rubber feet).  Use a small, flathead screwdriver and beware of power and data cables, as well as the camera up top.
• This isn’t a bad time to clean the laptop screen while you’re at it.  I used a paper towel I dampened, and added a drop of dish detergent to it.  Try not to get and soap or water into the sides of the display.  Take another damp paper towel to rinse it.
• Finally, this procedure is a bit more involved than ones before.  So, BE CAREFUL.  If you aren’t comfortable doing this, seek assistance.  And of course, do this at your own risk; I am not responsible for any damage to your laptop, yourself, or any other possession.

So, here it is:

Good luck.  This may help you, or it may not, but if the flickering has really been getting to you it’s worth a shot.  Overall, if you’re thinking of buying a G530, I’d recommend against it.  It’s pretty nice for a crappy machine, but it is a crappy machine.  But if you’re stuck with one, at least it’s not impossible to take apart.

In the meantime, though, I had a great dinner last night with my family.  I am in the USA, but I wish you all the best on our Thanksgiving holiday, no matter where you are.  Life can suck sometimes, other times it can be amazing.  Many of us have a lot to be thankful for, so take the time to reflect while you’ve got it.

My original draft was going to be something along the lines of how Steve Jobs was sort of overrated in that he was more a marketing genius as opposed to a great technological innovator, but at the same time was a very important figure who helped to make technology more accessible to the masses and inspire people.  Well, Dennis Ritchie was certainly more the innovator.  UNIX and C are the foundation of so much in computing, from microcontrollers all the way up to super computers, and they likely will be for a long time.

So, long story short, there are many ways to have an impact, and it doesn’t just have to involve appearing in front of large crowds in jeans and a turtleneck.