How I changed servers midstream

When upgrading this site, I replaced the underlying hardware as well. The old server was just a dead end in too many regards to be worth upgrading in place, and besides, being able to run new and old side by side for a time is helpful.

This type of maneuver is routine work for a professional sysadmin. But it’s been at least two years since I’ve done a similar maneuver at all, and at least five years since I did it with Linux.

When I built the new machine, I gave it a unique IP address. Turnkey Linux makes getting an operational LAMP stack trivial, and depending on what you want to run on that stack, you may even be able to get that installed for you too.

Unfortunately for me, the Geeklog migration tool doesn’t seem to work with WordPress 3.0.1. So I had to get WordPress running on my old hardware in order to migrate. I chose WordPress 2.0.11 because the 2.0 branch appeared to be the current branch when Justdave wrote his migration tool, and 2.0.11 ran without complaint on the dated versions of PHP and MySQL that were on my old server.

After importing the content, I used mysqldump to export my databases. Specifically:

mysqldump --opt -u [mysql username] -p [database name, probably wordpress] > wordpress.sql

I should have gzipped the file, but I didn’t.

gzip wordpress.sql

I then connected to the old server via FTP and transferred the file. Use your favorite file transfer method; I happened to have FTP set up for my internal network.

Uncompress the file if you compressed it:

gunzip wordpress.sql.gz

Then restore the file:

mysql -u [mysql username] -p [database name] < wordpress.sql

Or, if the database already exists, like in my case:

mysqlimport -u [uname] -p [database name] wordpress.sql

Then I connected to the webserver via my web browser. WordPress 3.0.1 saw the WordPress 2.0.11 database and informed me that it needed to be upgraded. So I let it do its thing, and a few minutes later, I had a functioning WordPress site with 10 years’ worth of legacy entries.

I messed around with it for a while. Finally, I decided to go live. And at this point, I should have physically moved the new server into its permanent home. I didn’t do that, so now when I decide to move the server, I’m going to have some downtime.

To flip the IP addresses, you need to know where your Linux box stores its IP address. Debian and Ubuntu both store it in /etc/network/interfaces. As far as I can tell, Red Hat and derivatives like CentOS store it in /etc/sysconfig/network-scripts/ifcfg-eth0, but I haven’t used Red Hat or a derivative in a long time, perhaps 2003.

If worse comes to worse, try something like this to determine where it’s stored:

grep -r [ip address] /etc/

I edited the appropriate file on both boxes, changing the IP address while leaving all of the other parameters unchanged.

I then issued the command ifdown eth0 on both machines.

On my new production server, I then issued the command ifup eth0. Depending on the Linux distribution, it might also be necessary to re-issue a default route command. I didn’t have to do that.

Depending on how much Linux/Unix cred you have at stake, you could just do it the Windows way and reboot the box. Or both of them.

Once I was satisfied everything was working, I powered down the old server and celebrated.

Weekly roundup: 6 Oct 2010

I used to do a weekly roundup every so often, just doing short takes on stuff that interested me as I found it. I haven’t done that in years; I thought I’d give it a whirl again. I don’t know how often I’ll do it, but it was fun.

Ars Technica says Intel’s neutral stance on Atom in servers is a mistake. Absolutely. A dual-core Atom gives plenty of power for infrastructure servers like Active Directory DCs, print servers, and other similar roles. Atoms could even handle many web server tasks.

Xeons are appropriate for database servers and application servers, but throwing them at everything is severe overkill. A lot of server tasks are more disk-bound or network-bound than CPU-bound.

I worked in a datacenter facility for several years that was literally at half capacity, physically. But they didn’t have enough power or cooling capacity to add much more to it.

The only way anything can be added there is to take something away first. Right-sizing servers is the only way to fix that. If they would yank a Xeon, they’d be able to replace it with several Atom-based servers and get a net gain in functionality per square foot and BTU.

Virtualization, a la VMWare, is an option, but one isn’t necessarily a drop-in replacement for the other.

Or, of course, Intel can sit back and wait for ARM to come in and save the day. ARM provides even more functionality per watt. And even though ARM doesn’t run Windows, it does run Linux, and Samba has reached the point where it can stand in for an Active Directory domain controller.

Is there a market out there for a domain controller that fits in a package the size of a CD/DVD drive and consumes less than 20 watts? I’m sure there is. And if Intel doesn’t want to deliver it, ARM and its partners can.

There may be some resistance to ARM, since some decision makers are nervous of things they haven’t heard of, but it should be possible to overcome that. Maybe you haven’t heard of ARM, but guess what? Do you have a smartphone? It has an ARM CPU in it. That PDA you carried before you had a smartphone? It had an ARM CPU in it. It’s entirely possible that your consumer-grade network switch at home has one in it too. Not your router, though. That’s probably MIPS-based. (MIPS is another one of those scary RISC CPU architectures.)

Put a solid operating system on an ARM CPU, and it can run with anything. I have ARM devices that only reboot when the power goes out. If it weren’t for tornado and thunderstorm season causing the power to hiccup, those devices could run for years without a reboot or power-down.

And speaking of ARM, I have seen the future.

Pogoplug is an ARM-based appliance for sharing files. You plug it in, plug USB drives into it, and share files on your home network and the Internet with it. At least, that’s how it’s marketed. But you can hack it into a general purpose Linux box.

Inside, there’s a 1.2 GHz ARM CPU, 256 MB of RAM, and another 256MB of flash memory. Not a supercomputer, but that’s enough power to be useful. And it’s tiny, silent, and sips power. You can plug it in, stash it somewhere, and it’ll never remind you that it’s there.
I’ve actually considered picking up a Pogoplug or two (they go on sale for $45 occasionally, and the slightly less powerful Seagate Dockstar is available for about $30 when you can find them) to run this web site on. Considering how surprisingly well WordPress runs on a 450 MHz Pentium II with 128 MB of RAM (don’t ask me how I know), I think a Pogoplug could handle the workload.

What stops me? I can build an Atom-based PC for less than $150, depending on what I put in it, and run Turnkey Linux on it. Under a worst-case scenario, Turnkey Linux installs in 15 minutes, and it doesn’t take me any longer than that to drop a motherboard and hard drive into a case. So I can knock together an Atom-based webserver in 30 minutes, which is a lot less time than it would take me to get the LAMP stack running on an ARM system.

But if I had more time than money, I’d be all over this.

A device similar to this with an operating LAMP stack on it ready to go is probably too much to ask for. A ready-to-go image running the LAMP stack, similar in form to the DD-WRT or Tomato packages that people use to soup up their routers, might not be. I think it’s a good idea but it isn’t something I have time to head up.

I don’t think I’ve mentioned Turnkey Linux before. I’ve played with it a little, and I’m dead serious that it installs in 15 minutes or less. Installing off a USB flash drive, it might very well install in five.

And it’ll run pretty happily on any PC manufactured this century. More recent is better, of course, but the base requirements are so modest they aren’t worth mentioning.

I’ve built dozens of Linux servers, but this is fantastic. Spend a few minutes downloading an image, copying it onto installation media, and chances are the installation process will take less time than all of that does.

It’s based on Ubuntu LTS, and comes in literally 38 flavors, with more to come after the next refresh is done.

They haven’t built their collection based on the current version of Ubuntu LTS yet because they’ve been distracted with building a backup service. But that’s OK. Ubuntu 8.04.3 still has a little life left in it, and you can either do a distribution upgrade after the initial install, or build a new appliance when the new version comes out and move the data over.

And if Ubuntu isn’t your thing, or you really want 10.04 and you want it now, or worse yet, Linux isn’t your thing, there’s always Bitnami (bitnami.org).

Linux appliances took a little while to get here, but they’re here now, and they work.

Working for Canonical doesn’t make you pro-Free Software?

Stuart Langridge works for Canonical. Canonical produces Ubuntu, a popular Linux distribution. Apparently, this means he favors proprietary software in some people’s minds.

Yes, this is the same Ubuntu Linux you can download freely. You can make copies of it and sell them, legally. You can modify it, if you have the ability and inclination. Just setting the record straight.

Canonical does what it has to do to get Linux working well on your computer. And it succeeds rather nicely. If a computer can run Windows XP or newer, it can run Ubuntu, and installing Ubuntu will be easier than installing Windows in many cases. The computer this website runs on was built on a variant of Ubuntu, and it literally took longer to burn the CD than it took to run the installation. It blew my mind.

This is a case of software being like religion.

I am Lutheran. Almost militantly so, to the annoyance of some people who know me. I break from the traditional Lutheran camp in two regards: favoring music in the service that was written during my lifetime, and not being uptight enough about doctrine. I take the concept of grace alone, faith alone very seriously, and to an outsider, that plus the Lutheran definition of grace–God’s riches at Christ’s expense–is enough to make you Lutheran. That’s good enough for me. Some vocal Lutherans expect you to be able to recite precisely what makes John Calvin a heretic. I neither know nor care about that. I read the Bible, in its entirety, and concluded that Calvin puts certain responsibilities on you, a human being, that Luther puts on God. Since I believe that God is more reliable than me, I concluded that the Lutheran view is safer. I believe that ought to be enough.

The big question is whether I care if I’m Lutheran enough for some people. And the answer is no, I do not. I just ignore the rants about heresy that I see on Facebook, or better yet, stay off Facebook for long stretches at a time, and go about my business.

I guess that’s easier said than done in the Free Software community. There are a lot more witch hunters in that group. I suppose the people who can’t write working code try to make up for it by concentrating on ideology, or something like that. I do know it’s a whole lot easier to crusade for ideology than to write code.

The silent majority of people just want a system that works. They don’t want to hunt down drivers and compile them, or spend hours editing configuration files. I can’t tell you how many e-mail messages I received over the years from people who tried the most popular Linux distribution of the time, ran into difficulty, and gave up. (It’s one reason my e-mail address isn’t on this site anywhere anymore.) Even if the problem was something I could answer relatively easily, they just gave up and installed Windows instead. In their minds, if Dave Farquhar knows how to make that work, then whoever made that particular Linux distribution ought to make it work automatically. And they have a point.

So if Ubuntu installs a driver or some other low-level code that isn’t completely Richard Stallman-approved, the majority of people really don’t care. They’re happy it works. If their freedoms are infringed upon, they don’t know it.

I’ve said before that I could re-train my mother to use Linux. In fact, she could probably get all of her work done in Linux and emacs, and I’m sure John the Baptist Richard Stallman would be absolutely thrilled. But it would take her several years to learn the nuances of emacs, and some of her job duties would take much longer. Perhaps she wouldn’t mind occasionally spending hours to do something that can be accomplished in minutes using a more specialized, albeit proprietary, tool. In the end, when she’s a master of emacs, I’ll be able to tell her that she’s free. And she’ll tell me, “It wasn’t worth it.” Or, if she’s feeling a little more reasonable, she’ll throw something at me.

It’s easier said than done. But perhaps when the witch hunters come knocking, it would help to ask them if they had anything better to do?

After all, he could be a total sell-out like me. In my job, I’ve recommended Linux-based solutions when appropriate, but I spend the overwhelming majority of my time supporting things that run on Windows. Perhaps they would prefer he do that.

But I wouldn’t. I really like the work Canonical is doing.

Why I still like Debian

Say what you will about Debian–the development process is slow and plodding, the distribution is always trailing-edge and Debian is always the last to get everything–but installing it today reminded me why I still like it.I need a temporary holding place where I can experiment. I want to move my genealogy page to a new piece of software, and I want to migrate this blog to WordPress.

The only spare computer I have right now that works reliably is an ancient P2-266. I don’t know how that ended up being, but I’ll work with it..

The system has 192 MB of RAM. I have a pile of DIMMs, but it doesn’t like most of them. So 192 it is.

Ubuntu’s installer won’t load on this system. It tries and tries, but after several hours, the only result is a graphical screen with a heron on it and a mouse pointer.

Debian just loads in text mode and doesn’t complain. It asks a few questions along the way, and it’s slower than the last few installs I’ve done, but it’s steady.

I’m confident I could get it to work on my 486 too, if I had the need or inclination (I don’t). I’ll save the 486 for the day I want to set up a DOS box for some old-school gaming. Probably in another 10 years.

My poor-man’s SSD boots DOS really fast

So, my no-name compact flash adapters arrived today. I ripped one open like a kid at Christmas, pulled a PC off the scrap heap, yanked my 128 MB compact flash card out of my PDA, and went to town.Unfortunately I couldn’t get Xubuntu to boot, let alone install a minimal configuration, because my CD was corrupt. I wasn’t sure if I could install anything in 128 MB, but my last Debian 3.0 install was smaller than that, so I held out hope.

So I grabbed a Windows 98 SE CD. Surely that would fit in 128 megs if I left out all of the optional components, right? And if not, there’s always Doublespace, right? Wrong. The installation bombed out, saying I needed 205 megs.

The original Win98 was smaller though, right? So I grabbed that CD. It wouldn’t play either. It repeated that same 205 meg line. I’ll bet it says that to all the guys.

So I grabbed my Win95B CD. I’m pretty sure I once crammed Win95B and Office 97 onto a 170 MB hard drive. It wasn’t pretty, but hey, it was an emergency. But no joy there either. The CD wouldn’t even read. I guess I shouldn’t be surprised since it’s a CD-R that I last touched sometime in 1999. I have no idea where the original CD is, but I know where the manual and COA are, not that that helps any.

I dug around for a Debian CD. I come across those fairly often when I’m looking for something else, but tonight I couldn’t find one.

I found my OS/2 3.0 sleeve, which got me thinking, but I couldn’t find the disc. I know I could make that fit in 128 megs and it would really scream–as in, it would complain loudly about the ATI video, and it would run really fast–but I never found the CD.

So for lack of anything else to put on it, I reinserted the Win98SE disc, rebooted, picked the Command Prompt with CD-ROM option, and dropped into DOS for perhaps the first time since the Clinton administration. I ran FDISK, blew away the partition table and repartitioned it, rebooted, found FORMAT.COM hidden in the WIN98 directory on the CD, formatted the drive, remembered I had to use the /S option, reformatted the drive, copied over himem.sys, oakcdrom.sys, mscdex.exe, and whatever else I could find, and built up config.sys and autoexec.bat files by hand using copy con, since I couldn’t find edit.com anywhere on the CD. I removed the CD, rebooted, and it booted fast–into an error message saying I’d neglected the /d parameter. Considering the last time I used the /d parameter was in 1999, that shouldn’t be surprising. What is surprising is that I remembered the syntax. So I deleted config.sys and autoexec.bat, built up new ones with copy con, and rebooted again.

The Win98 splash screen flashed, then I got a familiar DOS prompt, including indicators that the CD-ROM driver was working. It took about as long to boot as it did for the BIOS to do its thing–probably 1-2 seconds. Not bad for $7 worth of hardware ($5 for the adapter from Compgeeks, and $2 for the CF card from a garage sale).

Supposedly Windows 2000 can shrink down to 60MB if you get really aggressive with nLite. I’d really like to see that, but that means I’ll have to find my Windows 2000 CD. I’m sure it’s hiding somewhere in Argentina, playing cards with my OS/2 3.0 and Debian CDs.

I also ought to download Debian 3.0 again. I’m thinking 60-120 megs of Debian is probably more useful than 60 megs of Windows, but I really want to see how quickly Windows 2000 boots off flash.

Supposedly these cards support UDMA, so I probably ought to order some larger CF cards so I can do something really useful with them. Seeing DOS boot instantly is enough to convince me that these things can be useful. Who knows, I might be insane enough to try running my webserver off flash (the memory, not the obnoxious Macromedia/Adobe product).

Setting the MTU automatically in Debian

I run this website off a server running on an ADSL line in a spare bedroom of my home. That causes some weird issues from time to time, like the time I had to figure out setting the MTU automatically in Debian.

Why Debian?

My server of choice is Debian, because it’s Linux which makes it fast, reliable, and cheap, and Debian makes it pretty easy to install only what you want and need, so I can have a server OS that’s only using 125 megabytes of disk space, leaving most of my drive available for content. I like having space for content.

This will work in Debian-derived systems like Ubuntu and Linux Mint too.

PPPoE issues

Now, the downside of modern DSL: Southwestern Bell, like most ISPs these days, uses PPPoE. So not only can your IP address change with no notice whatsoever, you also have the hassles of PPPoE. With the default settings, some unknown but noticeably large percentage of web users won’t be able to access a web server running on a DSL connection using PPPoE.

The reason is MTU and fragmentation.Yes, you remember MTU if you used Windows 9x back in the bad old days of dialup. Tweakers would play around with the MTU settings in hopes of squeezing just a little more performance out of their 56K modems, and they would swear that one utility did a better job than any others, or that this MTU setting was optimal and the conventional wisdom of 576 stank… Remember those flamewars?

Well, with broadband, theoretically the right setting to use is 1500. Trouble is, PPPoE steals some of that packet space, and the result is something worse than slow speeds. In some scenarios, you completely vanish.

Setting the MTU

The way to make my website reappear is to issue the command ifconfig eth0 mtu 1472. The exact number doesn’t seem to matter much. It appears for me that 1472 is the maximum I can use. (It can vary from ISP to ISP, in case you’re wondering.)

Excellent. Problem solved.

Not so fast. Problem solved until my server reboots. Linux doesn’t need to reboot, right? Right you are. But here in St. Louis, the power likes to hiccup a lot, especially in the summertime. My server is on a UPS, but every once in a while, in the middle of the night, there must be a long enough power failure that my UPS dies, because every once in a while I fall off the ‘net again.

To set the default MTU permanently–that is, to change it automatically on bootup–one normally would change the ifup script or the rc.startup script. Except Debian doesn’t have either of those.

My kludgy solution: cron. Log in as root, issue the command crontab -e, and add the following line:

*/2 * * * * ifconfig eth0 mtu 1472

With this in place, only seconds will elapse between the time my power comes back on for good and I reappear on the ‘net. I can live with that.

More Debian tricks

If you change your network card or motherboard, you don’t have to reinstall Debian but you may lose eth0. Here’s how to get eth0 back. And here’s how to get a list of the installed packages in Debian.