Tidy up backup page, following raspberrypi#191

Author: bennuttall

linux/filesystem/backup.md

@@ -8,7 +8,7 @@ Here we'll guide you through some backup techniques for your Raspberry Pi system
 
 A sensible way to keep your home folder backed up is to use the `tar` command to make a snapshot archive of the folder, and keep a copy of it on your home PC or in cloud storage. To do this enter the following commands:
 
-```
+```bash
 cd /home/
 tar czf pi_home.tar.gz pi
 ```
@@ -19,26 +19,26 @@ This creates a tar archive called `pi_home.tar.gz` in `/home/`. You should copy
 
 If you have MySQL databases running on your Raspberry Pi, it would be wise to keep them backed up too. To back up a single database, use the `mysqldump` command:
 
-```
+```bash
 mysqldump recipes > recipes.sql
 ```
 
 This command will back up the `recipes` database to the file `recipes.sql`. Note that in this case no username and password have been supplied to the `mysqldump` command. If you do not have your MySQL credentials in a `.my.cnf` configuration file in your home folder, then supply the username and password with flags:
 
-```
+```bash
 mysqldump -uroot -ppass recipes > recipes.sql
 ```
 
 To restore a MySQL database from a dumpfile, pipe the dumpfile into the `mysql` command; provide credentials if necessary and the database name. Note that the database must exist, so create it first:
 
-```
+```bash
 mysql -Bse "create database recipes"
 cat recipes.sql | mysql recipes
 ```
 
-Alternatively, you can use the `pv` command (not installed by default, so install with `apt-get install pv`) to see a progress meter as the dumpfile is processed by MySQL. This is useful for large files:
+Alternatively, you can use the `pv` command (not installed by default, so install with `sudo apt-get install pv`) to see a progress meter as the dumpfile is processed by MySQL. This is useful for large files:
 
-```
+```bash
 pv recipes.sql | mysql recipes
 ```
 
@@ -48,29 +48,28 @@ It may be sensible for you to keep a copy of the entire SD card image, so you ca
 
 In Linux or Mac, for example:
 
-```
+```bash
 sudo dd bs=4M if=/dev/sdb of=raspbian.img
 ```
 
 This will create an image file on your PC which you can use to write to another SD card, and keep exactly the same contents and settings. To restore or clone to another card, use `dd` in reverse:
 
-```
+```bash
 sudo dd bs=4M if=raspbian.img of=/dev/sdb
 ```
 
 These files can be very large, and compress well. To compress, you can pipe the output of ```dd``` to ```gzip``` as well to get a compressed file that is significantly smaller than the original size:
 
-```
+```bash
 sudo dd bs=4M if=/dev/sdb | gzip > rasbian.img.gz
 ```
 
-To restore, pipe the output of ```gunzip``` to ```dd```:
+To restore, pipe the output of `gunzip` to `dd`:
 
-```
+```bash
 sudo gunzip --stdout rasbian.img.gz | dd bs=4m of=/dev/sdb
 ```
 
-
 See more about [installing SD card images](../../installation/installing-images/README.md).
 
 ## Automation