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CHAPTER 4 ■ HOME IS HOME the output waveform varies too and is usually governed by the cost of the device. The output of the cheaper devices is usually a square wave, while more expensive ones have a sinusoidal wave form. This doesn’t matter much for computers but can provide a difference when powering an audiophile record player, as mentioned in Chapter 3. Whenever a power drop is noticed, an alarm will sound and repeat the audible warning periodically. When the battery reaches a critically low level, the shutdown procedure will be initiated via the USB (or serial) cable so that the machine(s) connected to the UPS can close down safely. Each unit comes rated for a different VAs, indicating how much you can draw from it when it is disconnected from the mains. You will usually need a higher VA than the wattage. The required VA is the watts divided by the power factor of the connected device(s). The temporal duration of protection ranges from a few minutes to quarter of an hour, depending on what machines are connected to it and the tasks running on those machines. You can refer to Table 4-1 for a rough guide. For a buying, always get as high a power rating as possible. ■ Note With most UPS units, the power sockets will be divided between those that are powered in the event of an outage and those that aren’t. All sockets are generally protected against surges. Given, say, four powered sockets, you have to decide what devices will use it. Naturally, your server should be a given. That’s followed by the home’s internal router or switch so that a “shutting down” message can be sent and processed by the other machines on a UPS. (This is for the computers benefit only, since any human will have noticed the lights going out and will instantly panic knowing they haven’t hit the Save button on their application.) You may also want to keep the broadband router on the UPS also so that a warning message (via e-mail, for example) can be sent. This is usually a minor consideration, but if you work remotely with the machine, this will prompt you to ease up on any processor-heavy tasks so that the UPS can last for longer. ■ Note When the UPS is first installed, test it with the circuit breaker but not by pulling the plug out, which can introduce a floating ground that is dangerous to electronic equipment. The discussion of multiple servers reappears here, since it can be beneficial to have a low-power master server on the UPS, with the media-transcoding machine on its own UPS, to preserve the longevity of the main server and even finish recording that vital episode of Doctor Who you might have normally missed during the power cut! If both servers are fairly high power and you have only one UPS, then it is usually worth consolidating both into one box to limit the power drain on the unit. You might also consider keeping one powered socket for a monitor, perhaps connected to the second media server UPS unit. If you keep it turned off, it’ll draw very little power from the UPS, but in the event of a problem, you are able to see the machine running through its shutdown procedure, and you can ensure its closedown routine is working effectively. Without this, you will either have to trust the UPS software daemon is working or keep a laptop handy with a fully charged battery. 133 CHAPTER 4 ■ HOME IS HOME ■ Tip You can ensure your laptop is fully charged by using the crontab to switch on an X10 module for at least an hour every night. Once the hardware UPS is in place, you then need a way to detect that the power has gone and so begin the shutdown procedure. Most UPS units come with a USB cable (sometimes with a proprietary connector on one end, so don’t lose it!) that allows a PC to query the state of the unit. Those that don’t have one are not generally worth buying. Granted, they are cheaper, and your data is probably safe with the journaling filesystem you’ve already installed, but the extra cost and peace of mind knowing you’ll get a clean shutdown is worth it. ■ Note It is possible to mimic the shutdown functionality of a UPS by using heyu to monitor the power lines and, if it sees two (or more) lights going off at the same time, trigger a shutdown. But this method is liable to false positives and doesn’t work during daylight hours. Three primary packages are available to handle a UPS, all of which conflict if used together. They are apcupsd, nut-hal-drivers, and nut. I’ll cover the latter since it is the most recent, flexible, and actively developed. First, perform a traditional installation: apt-get install nut The setup procedure then involves creating four configuration files in your /etc/nut directory: # /etc/nut/ups.conf [apc] driver = usbhid-ups port = auto 7 This references the appropriate driver for your UPS unit, which I have called apc here: # /etc/nut/upsd.conf ACL all 0.0.0.0/0 ACL localhost 127.0.0.1/32 ACCEPT localhost REJECT all 7 134 The compatibility list is available at www.networkupstools.org/compat/stable.html. CHAPTER 4 ■ HOME IS HOME This indicates that only the local machine should react to UPS messages, which eliminates hackers spoofing a UPS failure and causing your machine to switch off. Then set up a basic user that has access to daemon by doing this: # /etc/nut/upsd.users [local_mon] password = mypasswordhere allowfrom = localhost upsmon master You can then configure the daemon by specifying its process commands: # /etc/nut/upsmon.conf MONITOR apc@localhost 1 local_mon mypasswordhere master POWERDOWNFLAG /etc/killpower SHUTDOWNCMD "/sbin/shutdown -h now" You can set up multiple users if you will be monitoring the UPS from alternate machines, but it’s not necessary, since you’ll probably create a web page holding this information. You can then fix the permissions for the files (since there’s a password in there you’d probably rather the world didn’t see): sudo chown root:nut /etc/nut/* sudo chmod 640 /etc/nut/* and start the daemon running, like so: upsdrvctl start /etc/init.d/nut start This can be made to start at every boot by editing the /etc/default/nut file. You can then query the state of a given UPS and check that it’s working by issuing the following command, where apc is the name given earlier: upsc apc The output is something like this: battery.charge: 100 battery.charge.low: 10 battery.charge.warning: 50 battery.date: not set battery.mfr.date: 2009/01/21 battery.runtime: 705 battery.runtime.low: 120 battery.type: PbAc battery.voltage: 13.5 battery.voltage.nominal: 12.0 driver.name: usbhid-ups driver.parameter.pollfreq: 30 driver.parameter.pollinterval: 2 135 CHAPTER 4 ■ HOME IS HOME driver.parameter.port: auto driver.version: 2.2.2 driver.version.data: APC HID 0.92 driver.version.internal: 0.33 input.transfer.high: 266 input.transfer.low: 180 input.voltage: 242.0 input.voltage.nominal: 230 ups.beeper.status: enabled ups.delay.shutdown: 20 ups.delay.start: 30 ups.firmware: 829.D2 .I ups.firmware.aux: D2 ups.load: 49 ups.mfr: APC ups.mfr.date: 2009/01/21 ups.model: Back-UPS ES 700 ups.productid: 0002 ups.serial: 5B0904T46000 ups.status: OL ups.timer.reboot: 0 ups.timer.shutdown: -1 ups.vendorid: 051d It is possible to have several UPS units controlled by a single server. This is usually beneficial since it allows your master server to handle all the system administration tasks, giving a single point of entry to the home network, which can be hardened as appropriate. Having gotten the machine to shut down, you need a way of making it start up again once the power is back on full-time. This becomes a hardware problem, and success is governed by whether there is an option in the BIOS to start up on power or similar. In the case of the NSLU2, you can physically hack the circuit board to perform the same task. It is also theoretically possible to hack the switch in a standard PC in a similar fashion, but it’s not recommended. The WOL trick covered earlier generally doesn’t work across the Internet since it is a Wake on LAN feature. And even if your machine isn’t behind a router or modem that filters out such packets, something else generally will be. If it’s vital for your home machine to be powered for as long as possible and your machine cannot be made to boot when the power is connected, then you can employ an NSLU (hacked as shown in Chapter 2) as a bootstrap to issue WOL commands to your various server machines. Backups There are only two important things to say about backups: • Do them. • Test them. Everything else is mere details. The first detail is whether these should be held on-site, that is, at home, or off-site in a remote location, such as a colocated server or hired virtual machine. In an ideal world, you would adopt both. Keeping them off-site helps minimize loss caused by local problems, while on-site backups are useful for 136 CHAPTER 4 ■ HOME IS HOME data that you cannot possibly store elsewhere, such as configuration scripts and network plans that you’d need to rebuild the HA system should there be major failure. The next detail is what data actually needs to be backed up. Again, in an ideal world, that would include everything on every machine in the house. In reality, you have to consider the cost of replacing the data and the time necessary to perform the backup. This usually boils down to anything that you’ve personally created, such as the following: • Photographs • Letters • Program code • Artwork • Digital video • Music Each member of the family will have their own list that they will be responsible for. You, as the HA administrator, will also want to back up the server configurations. From here you can decide on the technology needed to carry out this task. Programmers will already be aware of source control tools, such as Subversion (http://subversion.tigris.org/), and will be advocating their use. For the uninitiated, these tools don’t just keep a copy of the latest version; they keep data to re-create copies of all the versions you’ve ever created, allowing you to go back in time to see what you wrote last week and why that does (or doesn’t) work! For the most part, it’s a good choice for code and system configurations because, as a developer, you have the mind-set necessary to perform the necessary update-merge-commit cycle at every juncture. However, with some coaxing, most family members will become au fait with it. Accessing the files requires a Subversion client, and there are several to choose from (such as TortoiseSVN or SmartSVN) that also have versions for Windows, eliminating that support headache. This also gives family members the ability to access their files from outside the home with no extra effort or software. On the downside, however, you will have to educate the family that word processing documents are usually stored in a binary format and, as such, are nextto-impossible to merge together if they change the same file at home and at school. Nor is it particularly efficient to use source control for large files that change often, such as raw Adobe Photoshop images. ■ Note Subversion stores its own work files inside the current directory, meaning they will each be littered with .svn folders. This is only a mild nuisance for end users but can cause bigger problems when they appear in system configuration folders such as /etc. To make a direct copy of one set of files from one directory to another, you can probably use cp at the end of each day. However, this will wastefully copy files that haven’t changed, and so rsync was born. rsync is a very old copy and backup program but is still a venerable workhorse. I make backups of my code directory, for example, with this single line: 137 CHAPTER 4 ■ HOME IS HOME rsync -a code steev@remote-backup-host.com:~/backup/daily 8 I recover them (for testing ) with this: rsync -a steev@remote-backup-host.com:~/backup/daily code The options here perform a recursive update, while maintaining all symlinks, permissions, and user settings and is the most typical in home situations. The manual pages detail other possibilities. rsync does have two problems, however. The first is that it’s available primarily for Unix-oriented platforms. Versions are available for Windows (such as DeltaCopy and the version with Cygwin), but they take a little while to set up and can be tricky. The second issue is that it requires a password to be interactively given in order to log in to the remote site. This is a nuisance and prevents any kind of automatic backup. For a remote site to allow a user to connect without a password, they must first establish an alternative form of trust—in this case, the exchange of public keys. To copy from machine A to machine B, B must have a copy of A’s public key. To copy from machine B to machine A, A must have a copy of B’s public key. In our case, machine A is at home with our files, while B is a remote machine for backup. So, our home machine must generate a key for the user who’ll be doing the copying. ssh-keygen -t rsa which by default can be found in ~/.ssh/id_rsa.pub. This is then copied to the remote machine (perhaps using a password-directed rsync) and appended to the list of authorized keys that the remote user will accept: cat id_rsa.pub >> ~/.ssh/authorized_keys Once this is done, you should be able to rsync without a password: rsync -a --bwlimit=100 steev@remote-backup-host.com:~/backup/daily code Note that this limits the bandwidth (with the bwlimit argument) to 100 kilobytes per second so that other applications can make use of the Internet, since rsync and ssh are rather greedy when teamed up together. One potential administration problem that can exist here is for the home user to be refused a connection because the address from which they’re connecting does not match the one used in the key. This can happen when the hostname is something simply like linuxbox1 but appears to the remote machine as netpc-london-isproute-isp.com or something equally unhelpful. The target machine, by comparison, will usually have a fixed name since it must be addressable from the outside world. Since the home machine name might change (at the whim of the ISP), the easiest solution is to reverse all the instructions given here! That is, use the remote server to connect to the home server, generate a key for the remote server only, and reverse the arguments to the rsync command so that the remote server pulls the data from the home machine in order to perform the backup. It is curious to note that it is the direction of the connection that requires the authentication, not the direction of the copy process. 8 138 All backups are useless unless they’re tested, remember! CHAPTER 4 ■ HOME IS HOME ■ Note The root user cannot, by default, connect through ssh. Although it is possible to override this, it is not recommended, so create a new user, create the ssh key for them, and use their crontab to initiate the daily backup. Although this solves the problems for Linux and MacOS users, there still needs to be a solution for Windows. If you can afford the time, preparing rsync on Windows can be worthwhile. Alternatively, you might want to instill best practices into the family by introducing a manual backup solution that requires them to do something to back up their work. This is one area in which Subversion scores higher, because the workflow encourages this automatically. What can be done instead is to create a writable SMB shared area on the network that is accessible to everyone, and it is their responsibility to add their files to it every night before bed. You can then use rsync to back up this network folder remotely. There are several free and shareware utilities for Windows that provide the copy-based backup necessary for the first step. Of course, everything I’ve said assumes that you’re storing your data at home. In most cases that will be true, but it is now easier than ever to buy space on a remote server (through Amazon’s S3, for example, with a virtual machine), which means you never need to back up. Of course, backups are still being done (by the automated tools and support staff at the server provider), but they’re transparent to 9 you. In the cases of external storage, you would only want to store data that was fairly small in size since streaming a full movie from a remote server would be unwatchable, and having to wait until it had downloaded would be equally annoying and defeat the purpose. These situations are beneficial in some cases because they mean no personal data is ever stored at home. So if a burglar steals your laptop, you haven’t lost the novel you’ve been working on. Some people prefer to protect their private data in public, by using services such as Flickr, Google Docs, and YouTube. The situation is the same as earlier with the exception that, being free services, there are fewer warranties about loss of data. Indeed, Google Mail has a personal storage limit of just over 7GB, which allows you to back up your data by saving them as attachments in your mail account! Or by using gmailfs. There is also the possibility of backing up the physical items in your home, namely, your media. Although the importance in CDs and DVDs is in the packaging, it is possible to save the contents by ripping them (as we covered in Chapter 3) onto external hard disks and placing the drives themselves in storage, either held with friends, with family, or in a professional safe. You could probably arrange a pairing scheme with suitably technical friends who will store your collection of discs in return for you keeping theirs. The same pairing idea works if you both rsync your media to each other during quiet periods of network traffic, such as during the night, for example. 9 As a paranoid geek, I would personally make my own backups periodically, in addition to those made by someone else. 139 CHAPTER 4 ■ HOME IS HOME Hiding Your Home Having a home connected to the Internet provides a way of consuming your media when away from home, remotely configuring your machines, and checking that you did indeed turn the lights off. It also provides great bragging rights! However, having it connected in this is naturally a concern for some. Even with the technical security issues I’ll be covering in Chapter 5, there’s some extra scope for hiding your automated home in much the same way as you’d put a blanket over the valuables in the car when you park it. One way is to set up two domain names for your home machine. The first should be considered the public site, which provides a smoke screen, and may contain a web site and blog featuring your cat! By being the default web site, this will be used whenever the IP address is used alone. (I’ll cover the method when discussing virtual hosts in Chapter 5.) You can then additionally set up a second domain with access to your home automation web pages. You will still secure these pages, naturally, but this is a good first step. Although registering domain names is easy enough, it is not necessarily the best option when dealing with home machines, because your IP might change when a DHCP lease is not renewed at the whim of the ISP, and you’d have to wait another 24 hours for the DNS information to repropagate through the various DNS servers. Although this is unlikely, even if you decide to power down the server every night, better solutions are available by using dynamic DNS. The method assigns an arbitrary subdomain, from a known primary domain, to a given IP. Because subdomains do not need to be propagated by DNS before they can be used, they have a more immediate effect and can be registered for very little money—in most cases, zero. One such service is available from dyndns.org. After registering (also free!), you can create your own subdomain and point it to your home server. This subdomain can extend from one of several primary domains, such as homelinux.net, mine.nu, or dnsalias.com. The T&C requires that you update this record periodically to ensure it’s still active, but this can be done automatically with appropriate routers or through a package such as ddclient. This should be run periodically, either in daemon mode or from crontab, to keep their records up-to-date. The configuration simply requires your login credentials for DynDNS and the subdomain names you want to update. # /etc/ddclient.conf daemon=600 use=web, web=checkip.dyndns.com/, web-skip='IP Address' login=your-username password=your-password protocol=dyndns2 server=members.dyndns.org my.homelinux.net Because this is a DNS record, only the name is registered. It’s still up to you to support the services. But this is what you want, because it allows you to run your own servers for e-mail, the Web, SSH, and so on. You can hide behind more curtains by providing access only through an external proxy—a proxy whose existence and login is known only to you. The first step is to prepare the hosts.allow file with the following: sshd: LOCAL myhidden.privateserver.com 140 CHAPTER 4 ■ HOME IS HOME and add the paranoid inverse to hosts.deny: sshd: ALL As you can guess, when used in combination, this limits all SSH connections to those originating from the local (192.168.x.x) network and those on an external server that might be a colocated server, work machine, or shell account. ■ Note These rules can apply to all protocols, not just SSH, by changing sshd to ALL in the previous examples. This approach is not without risk, however, because should your server become inaccessible for any reason, you will be able to connect to it (and therefore solve the problem) only from the specified machines, which might be difficult if you are on vacation. ■ Note If your private server supports multiple domains, the name that is specified here to sshd must be the canonical one. You can extend this idea by controlling your house through an alternate protocol, such as Simple Object Access Protocol (SOAP), from a remote server, although this does open up two potential points of attack. Adding to Your Home The simplest way to incorporate automation into your home is through wireless—or at the least, automation that uses no new wiring. This second approach covers a surprisingly large amount of ground, including networking through WiFi and Ethernet over Power, appliance control (with X10 over the existing power cables), and media distribution (with TV senders.) But even then, with so many devices occupying the 2.4GHz range, there will be a limit to what is possible and how far it can be expanded. So, naturally, a wired approach will begin to win favor, which will require some drilling of holes and running of cables. In all the advice that follows, remember that you must always plan ahead, thinking about what each room will have in it, what it could have in it next year, and how it will be used. Running cables is a timeconsuming process and not something that wants to be repeated, so it’s better to lay too many and have unused sockets than it is to run out when you attempt to plug in a new gadget and find that you first need to buy an expanded unit. Cable is, after all, comparatively cheap when compared to the cost of installation or maintenance. Having two cables is a also useful redundancy measure in all the following examples, if you have the space to include them. 141 CHAPTER 4 ■ HOME IS HOME General Considerations Except in very esoteric cases, Node0 will always be at the center of your HA installation. Even if it is not physically close to the center of the house, all cables should be run into it. This is known as a star configuration. The process of running cables from one location to another is known as pulling cables, since it involves the act of pulling them through one set of holes to another. When you’re adding to an existing home, you will generally need to drill holes in the ceilings and pull cables down through wall-mounted trunking, as shown in Figure 4-1. With self-builds, you may have the opportunity to place the cables inside the walls themselves, making them invisible except for the wall plate beside the skirting board. Of course, if you’re doing some major redecorating, then you might decide it’s worth removing the wall and replastering to make the cabling invisible. Figure 4-1. Trunking to hide the cables and a volute to (try to) hide the join. Whichever approach you take, it’s best to pull all the cables at the same time: audio, Cat5, and coaxial. If necessary, buy four drums of network cable so you can pull multiple Cat5 cables through at the same time. This will save a lot of effort. ■ Note If you are planning a projector in any room, then you will generally need to run cables within the ceiling itself, which involves lifting the floorboards of the room above. When this is likely, do it earlier since you won’t want to do it later and might live without a projector; plus, you can take the opportunity to lay a lot more cables in the same space than you would normally. 142