Single User Mode Commands
Back in the old days of computing, you had no choice but to navigate through your file system using what is called a terminal. That was before the time of GUI or graphical user interface. This is the most basic form of interacting with your machine, this is an art. For a while now, my fellow techs and I would occasionally write a terminal article teaching you some of the simple commands.
By entering Single User Mode you can give basic commands to the UNIX shell of the Mac OS just as if you were typing on an old UNIX terminal. This is NOT to be confused with the Terminal App in your Utility folder. Single User Mode and Verbose Mode are only available upon boot-up by holding special keys to get to the UNIX shell.
Now you may ask why do I need to learn this? Well, it is what divides the average user from the power user. It is one of the most powerful tools a user has in their arsenal, it cuts right through the pretty wrapper of macOS GUI. Single User mode has a plethora of uses, including troubleshooting. Let’s say your Mac will not complete its login, OH NO!! With the power of UNIX, you can troubleshoot part of the issue using this handy tool! Let’s get started.
First, boot your Mac and hold the Command and S keys, you are going to see a bunch of crazy lines of text than just a blinking curser. Type ‘df -h’ this will get a read-out of the disk space and amount used. Many times your Mac may not boot because your drive is filled to the max. This means the filesystem has no space to make the temporary files it needs to function. We always recommend that you leave at least 10% of your drive’s capacity vacant. That means if you have a 1TB drive you need 100GB free.
With the ‘df-h’ command you can see you if you have enough space or if your drive is more stuffed then Uncle Phil around the holidays. But you have enough space, now what? Maybe your filesystem has become corrupted, no, not the type of corruption that we see in our nation’s capital. Trust me, your computer can be trumped by corruption and that is not locker room talk! So before you tweet to your buddies in an angry rage, try running ‘fsck -fy ‘which is a file system repair. Now before you try any of this BACK UP YOUR MACHINE, there is no confirmation or undo in single user mode, it is all or nothing.
Another command you can use is ‘config’, which will give a list of your internet interfaces, i.e. wlan0 or eth0. It will also tell you if you have what is called an IP address which looks like this 192.168.1.xxx the xxx are your subset that gives you your address. If your mac is getting an IP address and you still get no interwebs the issue might be with your web browser or router so what is the next step? The ping command to the rescue! It works like this, you type ‘ping’ and then the web address i.e, ping google.com. If you have an IP address and cannot speak with the outside world your DNS setting not be working or your router could be broken.
When navigating in single user mode it is easy to get confused and lost, so you can use the ‘pwd’ command or present working directory, to give you the ‘you are here’ or if you want to see what paths you can take try the ‘LS’ command. This will list the next paths you can take in the directory. I can’t go into all the uses of the single user mode, I would need a book for that and I have computers to fix. But, hopefully, I leave you today knowing a little more about single user mode.