I’ve started using a backup strategy based on that originally described by Jamie Zawinski and subsequently covered in Jeff Atwood’s What’s your backup strategy? article. It works by incrementally backing up your data to a bootable clone of your computer’s internal drive, in order to replace the internal drive when it fails.

This script is maintained in my dotfiles repo. Please report problems or improvements in the issue tracker.

This post is mainly to document – for myself as much as anything – the process I went through in order to implement an incremental backup strategy in OS X 10.6+. Use at your own risk. Feel free to suggest improvements if you know of any.

Formatting and partitioning the drive

With your backup drive in its enclosure, connect the drive to your Mac and open the Disk Utility application.

1. Click on the disk’s name. This should bring up a “Partition” tab in the right panel.
2. Click on the “Partition” tab.
3. Under “Volume scheme” select the number of partitions you need. Probably “1 partition” if it is to match your internal disk.
4. Under “Name” enter the volume name you want to use, e.g., “Backup”.
5. Under “Format” select “Mac OS X Extended (Journaled)”, which is necessary if the disk is to be bootable.
6. Click “Options” and check that “GUID Partition Table” is selected.
7. Click “Apply”.

This will format and partition the disk. The partition(s) should now show up in the Finder and on the Desktop.

Enable ownership permissions

The new partition needs permissions to be enabled to avoid chown errors when using rsync. To do this, select the partition and view its information page (using “Get Info” or Command+I). Expand the “Ownership & Permissions” section and uncheck “Ignore ownership on this volume”

Backup script

The backup script uses rsync – a fast and versatile file copying tool – to manage the copying and moving of data between volumes. You need to install rsync 3 (this is easily done using Homebrew: brew install https://raw.github.com/Homebrew/homebrew-dupes/master/rsync.rb). Rsync offers a wide variety of options and only copies the differences between the source files and the existing files in the destination, making it ideal for incremental backups. You can find out more about rsync in the rsync documentation

The following is the contents of a script I’ve named backup. I’m using it to backup all of the data on my internal disk, with a specified set of exceptions contained within a file called .backupignore.

#!/bin/bash

# Disc backup script
# Requires rsync 3

# Ask for the administrator password upfront
sudo -v

# IMPORTANT: Make sure you update the `DST` variable to match the name of the
# destination backup drive

DST="/Volumes/Macintosh HD/"
SRC="/"
EXCLUDE="$HOME/.backupignore"

PROG=$0

# --acls                   update the destination ACLs to be the same as the source ACLs
# --archive                turn on archive mode (recursive copy + retain attributes)
# --delete                 delete any files that have been deleted locally
# --delete-excluded        delete any files (on DST) that are part of the list of excluded files
# --exclude-from           reference a list of files to exclude
# --hard-links             preserve hard-links
# --one-file-system        don't cross device boundaries (ignore mounted volumes)
# --sparse                 handle sparse files efficiently
# --verbose                increase verbosity
# --xattrs                 update the remote extended attributes to be the same as the local ones

if [ ! -r "$SRC" ]; then
    logger -t $PROG "Source $SRC not readable - Cannot start the sync process"
    exit;
fi

if [ ! -w "$DST" ]; then
    logger -t $PROG "Destination $DST not writeable - Cannot start the sync process"
    exit;
fi

logger -t $PROG "Start rsync"

sudo rsync --acls 
           --archive 
           --delete 
           --delete-excluded 
           --exclude-from=$EXCLUDE 
           --hard-links 
           --one-file-system 
           --sparse 
           --verbose 
           --xattrs 
           "$SRC" "$DST"

logger -t $PROG "End rsync"

# Make the backup bootable
sudo bless -folder "$DST"/System/Library/CoreServices

exit 0

Adapted from the rsync script at Automated OSX backups with launchd and rsync

This is the contents of the .backupignore file.

.Spotlight-*/
.Trashes
/afs/*
/automount/*
/cores/*
/dev/*
/Network/*
/private/tmp/*
/private/var/run/*
/private/var/spool/postfix/*
/private/var/vm/*
/Previous Systems.localized
/tmp/*
/Volumes/*
*/.Trash

Adapted from the excludes file at Automated OSX backups with launchd and rsync

Every time the script runs, messages will be written to the system log.

Check that the source (SRC) and destination (DST) paths in the script are correct and match the volume name that you chose when partitioning the disk. Wrapping the $SRC and $DST variables in double quotes ensures that the script will work even if your volume names contain spaces (e.g. “Macintosh Backup”).

The command option --exclude-from tells the script where to find the file containing the exclude patterns. Make sure you either have .backupignore in the home directory or that you update this part of the command to reference the full path of the excludes file.

Running the backup script

You can run the script from the command line, or make it executable from the Finder or the Desktop:

1. Type the following into the command line to ensure that you have permission to execute the script:

   chmod +x /path/to/rsync_backup.sh
   

2. Remove the .sh extension from the script.

3. Create an alias of the script and move it to the Desktop.
4. Double click the icon to run the backup script.

It’s important to run the script regularly in order to keep the backup in sync with your internal disk. If you have a desktop computer, or you never turn off your laptop, you can automate the running of the script by setting up a cron job.

Checking the disk is bootable

Once you’ve run the backup script, you should test that the backup disk is bootable. To do this, restart your computer and hold down the Alt/Option key. Your backup disk should be presented, with the volume name you chose, as a bootable disk.

When I first booted my backup, the terminal displayed the following line:

dyld: shared cached file was build against a different libSystem.dylib, ignoring cache

According to this article, the fix for this is to update the cache by entering the following into the terminal:

sudo update_dyld_shared_cache -force

That should be everything you need to start implementing an incremental backup strategy when using OS X.

The git-checkout command can be used to update specific files or directories in your working tree with those from another branch, without merging in the whole branch. This can be useful when working with several feature branches or using GitHub Pages to generate a static project site.

The git-checkout manual page describes how the git checkout command is not just useful for switching between branches.

When <paths> or --patch are given, git checkout does not switch branches. It updates the named paths in the working tree from the index file or from a named <tree-ish> (most often a commit)…The <tree-ish> argument can be used to specify a specific tree-ish (i.e. commit, tag or tree) to update the index for the given paths before updating the working tree.

In git, a tree-ish is a way of referring to a particular commit or tree. This can be a partial sha or the branch, remote, and tag name pointers.

The syntax for using git checkout to update the working tree with files from a tree-ish is as follows:

git checkout [-p|--patch] [<tree-ish>] [--] <pathspec>…

Therefore, to update the working tree with files or directories from another branch, you can use the branch name pointer in the git checkout command.

git checkout <branch_name> -- <paths>

As an example, this is how you could update your gh-pages branch on GitHub (used to generate a static site for your project) to include the latest changes made to a file that is on the master branch.

# On branch master
git checkout gh-pages
git checkout master -- myplugin.js
git commit -m "Update myplugin.js from master"

The need to update my gh-pages branch with specific files from my master branch was how I first found out about the other uses of the checkout command. It’s worth having a read of the rest of the git-checkout manual page and experimenting with the options.

What is the cascade?

The cascade is a mechanism for determining which styles should be applied to a given element, based on the rules that have cascaded down from various sources.

The cascade takes importance, origin, specificity, and source order of style rules into account. It assigns a weight to each rule. When multiple rules apply to a given element, the rule with the greatest weight takes precedence. The result is an unambiguous way to determine the value of a given element/property combination.

Browsers apply the following sorting logic:

• Find all declarations that apply to a given element/property combination, for the target media type.

• Sort declarations according to their importance (normal or important) and origin (author, user, or user agent). From highest to lowest precedence:

  1. user !important declarations
     
  2. author !important declarations
     
  3. author normal declarations
     
  4. user normal declarations
     
  5. user agent declarations

• If declarations have the same importance and source, sort them by selector specificity.

• Finally, if declarations have the same importance, source, and specificity, sort them by the order they are specified in the CSS. The last declaration wins.

What is specificity?

Specificity is a method of conflict resolution within the cascade.

Specificity is calculated in a very particular way, based on the values of 4 distinct categories. For explanatory purposes, the CSS2 spec represents these categories using the letters a, b, c, and d. Each has a value of 0 by default.

• a is equal to 1 if the declaration comes from a style attribute in the HTML (“inline styles”) rather than a CSS rule with a selector.
• b is equal to the number of ID attributes in a selector.
• c is equal to the number of other attributes and pseudo-classes in a selector.
• d is equal to the number of elements and pseudo-elements in a selector.

The specificity is given by concatenating all 4 resulting numbers. More specific selectors take precedence over less specific ones.

For example, the selector #id .class[href] element:hover contains:

• 1 ID (b is 1)
• 1 class, 1 attribute selector, and 1 pseudo-class (c is 3)
• 1 element (d is 1)

Therefore, it has a specificity of 0,1,3,1. Note that a selector containing a single ID (0,1,0,0) will have a higher specificity than one containing any number of other attributes or elements (e.g., 0,0,10,20). This is one of the reasons why many modern CSS architectural patterns avoid using IDs for styling purposes.

What is inheritance?

Inheritance is distinct from the cascade and involves the DOM tree.

Inheritance is the process by which elements inherit the the values of properties from their ancestors in the DOM tree. Some properties, e.g. color, are automatically inherited by the children of the element to which they are applied. Each property defines whether it will be automatically inherited.

The inherit value can be set for any property and will force a given element to inherit its parent element’s property value, even if the property is not normally inherited.

About !important

The above should make it apparent that !important is a separate concept to specificity. It has no effect on the specificity of a rule’s selector.

An !important declaration has a greater precedence than a normal declaration (see the previously mentioned cascade sorting logic), even declarations contained in an element’s style attribute.

[CSS terminology reference]

Translations

• CSS: каскад, специфика и наследование

I recently moved from London to San Francisco to work at Twitter, as a Software Engineer. This is a rough guide – in the spirit of @chanian’s tutorial for Canadians – based on my experience of relocating, the mistakes I made along the way, and some information I wish I’d had. Use it at your own risk – don’t assume any legal truths; research things for yourself before making decisions!

I’m not going to cover anything about the US visa process. The company that has offered you employment in the US is likely to work with immigration lawyers who will handle (or guide you through) the visa application and processing. I’m also going to assume that your employer is providing temporary accommodation or that you are organising your own (e.g., via Airbnb) while you search for an apartment. Most of this article relates to things you will need to do once you arrive in San Francisco and soon after, but that you should spend some time thinking about beforehand.

Get a phone

You’ll need a US mobile/cell number pretty quickly, especially if you’re apartment-hunting.

The US telecom market isn’t great and will leave you nostalgic for the halcyon days of the EU-regulated, pro-consumer market you’ve left behind. For example, it’s now illegal to unlock a phone from a carrier unless you have that carrier’s permission to do so. Furthermore, if you do get a phone from a carrier (as part of your contract deal), you should be aware of whether or not you will be locked into a proprietary network, like Verison’s CDMA. Without a US credit history, you should expect to pay a sizable deposit when entering into a contract.

One way to reduce the cost of a phone contract is to bring your own phone to the party. If you bring a phone from the UK, make sure to check that your charger will work on US voltage. With an unlocked, GSM-supporting phone you can look to carriers like T-Mobile who offer various “value” and no-annual-contract plans. These prices are significantly cheaper because they don’t subsidise the purchase of a new phone. You’re likely to find “unlimited” data plans easier to come by than they are in the UK.

You’re shit-out-of-luck if you’re thinking you’d prefer a European-style pay-as-you-go (PAYG) approach. The options are thin on the ground. Any airtime you buy means just that – any time you spend talking or texting – so you pay to send and receive calls or SMS’s. My experience suggests that some networks recycle phone numbers or sell on your details. I still receive random texts addressed to previous owners of my phone number, and get messages from marketing companies who have miraculously acquired my personal details, an irritation that is compounded by the fact that it costs you money to be harassed.

If you’re determined to go the PAYG route, the nearest US equivalent is probably AT&T’s GoPhone SIM or Net10. You’ll have to purchase a phone and credit up front; top ups can be purchased in store, at some supermarkets, or done over the phone. This may also be the first time you encounter the US concept of a “restocking fee” – a method of dissuading you from returning items by charging you to do so. The restocking fee for the burner phone I first purchased was almost as much as the phone itself.

Open a bank account, transfer money

Make this a top priority. You should open a bank account as soon as you arrive in the US, especially as some banks will initially let you do so without a Social Security Number or permanent address.

Until you open a US bank account, you’ll be haemorrhaging money on fees levied by your UK bank for dollar transactions, and subject to poor exchange rates.

Choose a bank

San Francisco has a large range of different bank brands to choose from, but you’re probably best sticking to the big name banks that have branches and ATMs throughout the city, such as Bank of America, Chase, or Wells Fargo. There are co-ops and niche services if that’s your thing. Be sure to do some preparatory research on which bank is best suited to your needs. It’s also worth checking if your bank in the UK has a reciprocal agreement with any bank operating in San Francisco; it may cut down the cost of moving your money. Friends recommended going with either Bank of America or Chase. I went with Bank of America, where the customer service was personal and friendly.

Banking fees are a matter of course in the US. In contrast to the UK, you’ll almost certainly be charged for withdrawing money from any ATMs that aren’t owned by your bank. You have to buy cheque books (“check” in American English) and pay a fee to transfer your money to accounts outside your bank. Accounts usually involve a monthly fee, although this is waived in certain situations, such as setting up your salary to be directly deposited. Expect to set up a current (“checking”) and savings account, and to be asked to make a minimum cash deposit to complete the process (at Bank of America it was $100).

Once you’re all set up, your debit card will be sent in the post – so make sure you’ll be at that address for at least another week. In the meantime you may get a temporary cash card to get at what you’ve already deposited. Even if you transfer more money in, your bank can limit the amount you can withdraw within the first 30 days of the account being open – presumably to combat fraud/laundering.

Transfer money

It’s essential that you transfer money from your UK bank as soon as possible. There are many factors to consider when calculating how much money you want to transfer.

• You may enter the US up to 10 days before your visa is valid and you can start work.
• You need money for food, transport, going out, a phone (and deposit), apartment applications, an apartment deposit, buying furniture, etc.
• You might not be able to get paid until you have a Social Security Number.
• You’re unlikely to get paid until the middle or end of the month you start working.
• You’re very likely to get your first pay cheque given to you as a real cheque; your bank is then likely to withhold the vast majority of the cheque’s value for up to 28 days.
• It will cost you several thousand dollars – a deposit and at least one month of rent – to secure an apartment. In general, landlords will not accept a UK banking cheque.
• You’ll have to buy furniture and general household items if you aren’t shipping any from the UK.

All in all, this means you may end up without any significant US-earned money in your account for 30-45 days while making some of the biggest expenses you’re likely to have made for a while.

Transferring money to a US bank account can be done online via wire transfer between banks. Unfortunately, my bank in the UK – Santander – didn’t allow online wire transfers so I had to look for alternatives. You may want to research this prior to leaving the UK!

The Post Office provide a simple, secure, and fee-free service, but a poorer exchange rate. Looking around, I came across Currencyfair – a peer-to-peer currency exchange service. They provide online quotes without the need to sign up, they were very prompt and helpful in their replies to questions I had, and the exchange rate was very good. Overall, I saved quite a bit of money and I’d rely on them in the future.

Get a Clipper card

The Clipper card is San Francisco’s equivalent of London’s Oyster card. Getting one will take some of the pain out of using the various modes of public transport in San Francisco. You can get a Clipper card online and I’d suggest setting up “Autoload” (you’ll need a bank account) to get the card for free and never worry about remembering to top up your credit. Alternatively, you can buy them on the high street from shops like Walgreens.

Get a Social Security Number

Social Security recommend that you only apply for a Social Security Number once you’ve been in the US over 10 days.

My experience was that the process is quick and simple. You complete a short SSN application form ahead of time and take it to the nearest Social Security office along with the documentation they advise you to bring. Arrive first thing in the morning to avoid any wait. It can take a few weeks for your Social Security card to arrive so you may want to have it sent to your employer’s address if you don’t have a permanent address yet.

Once you have your Social Security Card, you should keep it safe and be judicious in giving your SSN out. However, you should provide it to your bank and employer as soon as possible.

Find somewhere to live

Living in the city of San Francisco is just one of the (more expensive) options available to you. I chose to live in the city but many of my friends and colleagues live in other areas, like the East Bay. Have a look around before making up your mind.

Rent is very expensive in San Francisco, even compared to prices in London, especially since it’s very rare to find furnished accommodation. It also appears to be rising at a staggering rate. However, buildings constructed before June 1979 are covered by San Francisco Rent Control which heavily constrains the rate at which your rent can increase once you become a tenant. Therefore, it’s worth taking the time to find somewhere that you could imagine living for a few years.

The rental market is extremely competitive. Many places rely on one-off, brief, herd-style viewings where you’re in the apartment with half a dozen other desperate people at the same time, and more arriving every minute. People hand over all their paperwork and a cash application fee (if applicable) there and then.

Things are made slightly harder because you’re unlikely to have any US credit history, which is something quite important over here. But an offer letter and salary details from a tech company seems to put you in good shape. It’s in your best interest to put together a dossier of papers to provide alongside any application you make. You should include scans of your employer’s offer letter, your visa, and ideally character references from a previous landlord, etc. Print out several copies to take with you to viewings. You might have to pay $30-$40 to make an application (which is meant to cover credit history checks), but I never did.

I found that using Craigslist or a listing aggregator like Lovely was the best way to find apartments for rent in the city. They will also help you to narrow your focus to the neighbourhoods that you’re most interested in (spend some time learning about the city). Before moving to San Francisco, I heard a lot of stories about how it was essential – if you are to have any hope – to be “first” to make contact with the poster of a listing, but my experience was that you’re generally given the date and time of a mass-viewing to attend. This means that making a good impression in person, and having a bit of a chat with your potential landlord or building-manager, is likely to improve your chances and help you make a decision. Be prepared for it to take a while to find an apartment – it took me over a month of searching.

Once you’ve found a place to rent and signed all the paperwork, call PG&E to create an account to pay for your heat and electricity. You can set up e-bills and automatic payments online once your account has been processed. It’s a good idea to sort out an ISP before you move in – I went with Sonic.net. Again, the monthly cost (which I was told includes 17 different taxes and “renting” of the router) is a little higher than you’d expect in the UK, and you can expect to pay an installation fee. Other things to do: get Renters Insurance and have your bank automatically mail out your monthly-rent check to your landlord or building manager. All these things are quick and easy to do.

If you’re interested in your renters rights, you can search the California Department of Consumer Affairs for information.

Buying stuff for your place

You’re going to need furniture and basic household items. There’s always Ikea, which is located in Emeryville across the bay. If you have any previous Ikea experience, you’ll know that it’s one of the most stressful shopping experiences imaginable. The Ikea in Emeryville is even worse but the prices are pretty good. You can get there by bus from San Francisco and have large items delivered, or sort out your own transport.

Other stores to look at include West Elm and Crate & Barrel; they sell nicer things but are significantly more expensive. Alternatively, there are a lot of independent and second-hand furniture shops in San Francisco, particularly in the Mission district and a few along Van Ness. They’re well worth checking out. Van Ness also has 3 or 4 stores that sell mattresses – Sleep Train came particularly well recommended. I’d suggest that you leverage the lower costs of similar mattresses online in order to significantly reduce the price of your purchase, while benefiting from the great service, free delivery, and returns policy of the high-street stores. And if you have no idea what you’re doing: home decor tips, infographics, and cheat sheets

Get a California I.D.

Once you have your SSN and have found a permanent address, you should apply for a California I.D. at the DMV. This is handy if you don’t want to carry your passport (with visa) around and don’t have alternative I.D., such as a driver’s licence. You should register for an appointment to avoid a long wait in line. It can take up to 60 days for your California I.D. to arrive.

Get a credit card

The U.S. revolves around consumer credit. You need to start building up a credit history as soon as possible if you want to avoid paying large deposits or higher prices. Ask your bank about the soonest that you can apply for a credit card and then start using it – buying on credit even if you don’t need to.

Inform HMRC and the Student Loans Company

Once you’re settled, you should make time to inform HMRC that you’ve left the UK. They’ll be able to assess your tax status. If you are repaying student loans, after 3 months in the US you’re expected to contact the Student Loans Company by completing an overseas income assessment form. They will then work out your repayments.

Welcome to the United States of America

Hopefully you settle in within a couple of months and get to know San Francisco. There are many faces to this city, but the social scene is pretty diverse and there are many restaurants, bars, cafes, parks, and attractions – plenty of places to explore and things to do while you find your feet.

For the first time since coming back to San Francisco in January, I had everything I needed for a saunter across the city in the sun: a means of taking photos / videos, a pair of sunglasses, no work, no plans, and no excuse.

On the morning of July 4th, I decided to spend the next couple of days offline. I read a book, and decided to go for a walk the rest of the day. I didn’t have any expectations or intended destination. I left my apartment at 2pm and decided to walk west, as I haven’t spent any proper time on that side of the city.

I passed through a couple of small parks and quiet neighbourhoods before hitting the edge of The Presidio.

At this point, I realised how long it had been since I’d seen a large expanse of something approximating nature. The Presidio was beautifully tranquil, with just a handful of people strolling or running through the trees. Walking off the trails, I saw a lizard for the first time in years; probably a San Francisco Alligator Lizard.

I exited The Presidio somewhere near the golf course and picked a long road to keep walking west.

On the way, I hit a main road and stood at the traffic lights. While I waited a young woman walking her dog struck up the first of several impromptu conversations I had with strangers that day. She must have seen me looking around for the street name, as she asked, “Are you lost? Are you a tourist? Where are you going?”

“I’m not sure. That way”, I said pointing down the long road before us.

She laughed. “See, you are lost!”

We chatted for a few blocks before our paths diverged. She told me that I would find some nice trails, and a good view of the Golden Gate Bridge, in the woodland near Lands End. It was dead ahead for another 30 minutes. So that’s where I went.

I hit the trails at about 4:30pm. It must have been close to perfect weather. Really sunny, warm, only a mild breeze, and the bay was completely clear. I wandered around for over an hour; perching near the edge of cliffs, taking in the sight of the Golden Gate Bridge on my right and a vast expanse of ocean to my left. Such a relaxing place.

I made time for a Dorsey-like Vine (my first Vine)…

On the way back, I crossed a road to take a photo. A post-middle-age man crossed my path, struck up a conversation, and began to tell me about his life in San Francisco “back in the day”. As if he could peer into my soul, he assured me that there was nothing wrong with being a software engineer (although he did initially think I was an estate agent; that was one of the first things he said to me).

My spirits further lifted by a stranger’s validation, I continued home. For last 30 minutes all I could think about was lying down, resting my feet, and eating. I’d been walking for nearly 6 hours. I’ll definitely do it again, but a skateboard would be helpful next time.

Material brought illegally in vehicles that had permission to carry fruits and vegetables

Plenert, Gerhard Johannes, author

Godfrey, Paul C., author

Munson, Chuck, author

Council of Supply Chain Management Professionals, author