Put a sheep in your first-aid kit.
Anne over at Hunt Gather Study Medicine discusses the problems with pre-packaged first-aid kits and reminds us that knowledge and experience are more important than gear.
Bitcoins are not a value-store.
When I first learned about the Bitcoin currency a few years ago, it didn’t excite me. A purely digital currency tied to no material good seemed an interesting project, but I didn’t see that it could have the practical value of, say, a digital gold currency. When the media blitz occurred last year I took another look and reached the same conclusion. A few months later I realized I was looking at the currency all wrong: bitcoins are not a value-store, they’re a means of exchange.
It doesn’t matter that Bitcoins are the digital equivalent of a fiat currency, with no inherent value. It doesn’t matter if their value fluctuates in relation to other currencies. There’s no reason to store wealth in Bitcoins (unless you’re a gambler). When you need to send money, purchase some Bitcoins and send them. When you need to receive money, accept Bitcoins and exchange them immediately for another currency. The value of the bitcoins only need to remain stable for the amount of time it takes to complete a transaction.
You are responsible for your own privacy.
Every so often there are stories announcing the fact that emails are not legally protected or that G-men can access email older than 180 days without a warrant. There will be some minor uproar, complaining about how outdated the law is, but here’s the thing: it’s irrelevant.
You don’t need to trust your service provider. You don’t need to trust your storage provider. You don’t need the law to protect you. You simply need to take a little self-responsibility and encrypt your data.
Any private data stored on hardware that you do not physically control should be encrypted (and it’s a good idea to encrypt private data on hardware that you do physically control). Problem solved. Unless you’re in the UK.
MediaGoblin has launched a crowdfunding campaign.
I’ve been following the development of MediaGoblin and OpenPhoto for about a year. Both offer decentralized and federalized photo sharing services, and promise to be excellent solutions for when Flickr finally dies. OpenPhoto currently feels more mature, but MediaGoblin is more ambitious in scope. I hope to see both of them succeed. Today, MediaGoblin announced a crowdfunding campaign to fund development. I’ll be donating.
Other projects prevented an overnight trip.
But I did get out for a ride along the Snohomish and Skykomish rivers on Saturday.
That Emily Chappell is cycling around the world.
She quit her job as a London bike messenger and left the UK in September of 2011. Currently she is in Korea, having cycled across Eurasia. I was made aware of her blog a couple months ago and was immediately hooked. I went back to the very beginning and read the blog all the way through. There are not very many blogs out there that I can say that about.
Back It Up: A Solution for Laptop Backups
A laptop presents some problems for reliably backing up data. Unlike a server, the laptop may not always be turned on. When it is on, it may not be connected to the backup medium. If you’re doing online backups, the laptop may be offline. If you’re backing up to an external drive, the drive may not be plugged in. To address these issues I wrote a shell script called backitup.sh.
The Problem
Let’s say you want to backup a laptop to an external USB drive once per day with cryptshot.
You could add a cron entry to call cryptshot.sh at a certain time every day. What if the laptop isn’t turned on? What if the drive isn’t connected? In either case the backup will not be completed. The machine will then wait a full 24 hours before even attempting the backup again. This could easily result in weeks passing without a successful backup.
If you’re using anacron, or one of its derivatives, things get slightly better. Instead of specifying a time to call cryptshot.sh, you set the cron interval to @daily. If the machine is turned off at whatever time anacron is setup to execute @daily scripts, all of the commands will simply be executed the next time the machine boots. But that still doesn’t solve the problem of the drive not being plugged in.
The Solution
backitup.sh attempts to perform a backup if a certain amount of time has passed. It monitors for a report of successful completion of the backup. Once configured, you no longer call the backup program directly. Instead, you call backitup.sh. It then decides whether or not to actually execute the backup.
How it works
The script is configured with the backup program that should be executed, the period for which you want to complete backups, and the location of a file that holds the timestamp of the last successful backup. It can be configured either by modifying the variables at the top of the script, or by passing in command-line arguments.
$ backitup.sh -h
Usage: backitup.sh [OPTION...]
Note that any command line arguments overwrite variables defined in the source.
Options:
-p the period for which backups should attempt to be executed
(integer seconds or 'DAILY', 'WEEKLY' or 'MONTHLY')
-b the backup command to execute; note that this should be quoted if it contains a space
-l the location of the file that holds the timestamp of the last successful backup.
-n the command to be executed if the above file does not exist
When the script executes, it reads the timestamp contained in the last-run file. This is then compared to the user-specified period. If the difference between the timestamp and the current time is greater than the period, backitup.sh calls the backup program. If the difference between the stored timestamp and the current time is less than the requested period, the script simply exits without running the backup program.
After the backup program completes, the script looks at the returned exit code. If the exit code is 0, the backup was completed successfully, and the timestamp in the last-run file is replaced with the current time. If the backup program returns a non-zero exit code, no changes are made to the last-run file. In this case, the result is that the next time backitup.sh is called it will once again attempt to execute the backup program.
The period can either be specified in seconds or with the strings DAILY, WEEKLY or MONTHLY. The behaviour of DAILY differs from 86400 (24-hours in seconds). With the latter configuration, the backup program will only attempt to execute once per 24-hour period. If DAILY is specified, the backup may be completed successfully at, for example, 23:30 one day and again at 00:15 the following day.
Use
You still want to backup a laptop to an external USB drive once per day with cryptshot. Rather than calling cryptshot.sh, you call backitup.sh.
Tell the script that you wish to complete daily backups, and then use cron to call the script more frequently than the desired backup period. For my local backups, I call backitup.sh every hour.
@hourly backitup.sh -l ~/.cryptshot-daily -b "cryptshot.sh daily"
The default period of backitup.sh is DAILY, so in this case I don’t have to provide a period of my own. But I also do weekly and monthly backups, so I need two more entries to execute cryptshot with those periods.
@hourly backitup.sh -l ~/.cryptshot-monthly -b "cryptshot.sh monthly" -p MONTHLY
@hourly backitup.sh -l ~/.cryptshot-weekly -b "cryptshot.sh weekly" -p WEEKLY
All three of these entries are executed hourly, which means that at the top of every hour, my laptop attempts to back itself up. As long as the USB drive is plugged in during one of those hours, the backup will complete. If cryptshot is executed, but fails, another attempt will be made the next hour. Daily backups will only be successfully completed, at most, once per day; weekly backups, once per week; and monthly backups, once per month. This setup works well for me, but if you want a higher assurance that your daily backups will be completed every day you could change the cron interval to */5 * * * *, which will result in cron executing backitup.sh every 5 minutes.
What if you want to perform daily online backups with Tarsnapper?
@hourly backitup.sh -l ~/.tarsnapper-lastrun -b tarsnapper.py
At the top of every hour your laptop will attempt to run Tarsnap via Tarsnapper. If the laptop is offline, it will try again the following hour. If Tarsnap begins but you go offline before it can complete, the backup will be resumed the following hour.
The script can of course be called with something other than cron. Put it in your ~/.profile and have you backups attempt to execute every time you login. Add it to your network manager and have your online backups attempt to execute every time you get online. If you’re using something like udev, have your local backups attempt to execute every time your USB drive is plugged in.
The Special Case
The final configuration option of backitup.sh represents a special case. If the script runs and it can’t find the specified file, the default behaviour is to assume that this is the first time it has ever run: it creates the file and executes the backup. That is what most users will want, but this behaviour can be changed.
When I first wrote backitup.sh it was to help manage backups of my Dropbox folder. Dropbox doesn’t provide support client-side encryption, which means users need to handle encryption themselves. The most common way to do this is to create an encfs file-system or two and place those within the Dropbox directory. That’s the way I use Dropbox.
I wanted to backup all the data stored in Dropbox with Tarsnap. Unlike Dropbox, Tarsnap does do client-side encryption, so when I backup my Dropbox folder, I don’t want to actually backup the encrypted contents of the folder – I want to backup the decrypted contents. That allows me to take better advantage of Tarsnap’s deduplication and it makes restoring backups much simpler. Rather than comparing inodes and restoring a file using an encrypted filename like 6,8xHZgiIGN0vbDTBGw6w3lf/1nvj1,SSuiYY0qoYh-of5YX8 I can just restore documents/todo.txt.
If my encfs filesystem mount point is ~/documents, I can configure Tarsnapper to create an archive of that directory, but if for some reason the filesystem is not mounted when Tarsnapper is called, I would be making a backup of an empty directory. That’s a waste of time. The solution is to tell backitup.sh to put the last-run file inside the encfs filesystem. If it can’t find the file, that means that the filesystem isn’t mounted. If that’s the case, I tell it to call the script I use to automatically mount the encfs filesystem (which, the way I have it setup, requires no interaction from me).
@hourly backitup.sh -l ~/documents/.lastrun -b tarsnapper.py -n ~/bin/encfs_automount.sh
Problem Solved
backitup.sh solves all of my backup scheduling problems. I only call backup programs directly if I want to make an on-demand backup. All of my automated backups go through backitup.sh. If you’re interested in the script, you can download it directly from GitHub. You can clone my entire backups repository if you’re also interested in the other scripts I’ve written to manage different aspects of backing up data.
Bitcoins are not insecure.
I’m no Bitcoin evangelist. I have my reservations about the currency. But one common critique that consistently angers me is that bitcoins are not secure because there have been instances of theft. This is equivalent to claiming that Federal Reserve Notes are insecure because people get mugged. Secure your shit.