./backlog: Charlie's blog

meanderings through tidbits of mathsy computery stuff

The Root of All Evil

Logging into a Unix machine as root is almost always a bad idea. I've come to this conclusion through several years of making silly mistakes and breaking important things on my own machines... usually mistakes that end up with me reinstalling my operating system. After destroying my system for the nth time because I was doing things as root, I decided to write this blog post - mostly as a reminder to myself not to be an idiot, but perhaps this will be useful to others, too.

Multi-user madness

If you allow root logins on a multi-user system (and freely give out access to the root account), you remove all accountability and essentially defeat the purpose of the system's authentication logs. Allowing multiple users administrative access to a machine means that any commands executed show up in the system logs as being executed by... root, and not the actual user.

This is a bad idea. Take the following hypothetical situation:

A development team of several people all have root access to a production machine. A team member has recently been fired or made redundant and harbours a grudge. The system administrator has forgotten to remove their SSH key or removed the wrong key by mistake, leaving the aggrieved ex-employee with root access to a machine. Something magically goes wrong with the production system shortly afterwards - all of their databases are dropped (oh no!) and all of the backups are nowhere to be found.

The system administrators know that the damage was most likely caused by the ex-employee, but the logs just point to the root user - and as several people were able to log in as root, nobody could prove that the ex-employee had anything to do with it.


Human stupidity beats artificial intelligence

Almost everybody that's ever installed or configured a Unix system or that has regularly used Linux themselves will have some experience of catastrophically breaking their system without meaning to. Whether through inexperience, incompetence, inattention, or just plain old bad luck, most Unix users will have a story along the lines of:

"I was formatting a USB thumb drive when I accidentally typed in sdb1 instead ofsda1 and for some reason, my computer wouldn't boot any more"

Or perhaps:

"I was trying to rm -rf /etc/nginx/* but I accidentally left a space between /etc/nginx and /* and it deleted everything on my filesystem partition"

Or maybe it'll be:

"I remember the time when I deleted some random file called libc.so to save disk space, and I was really surprised when everything stopped working"

Accidents happen, typos happen, and people do stupid things without thinking - it's part of human nature. There are so many Unix horror stories (like this, or these) that you really don't need to read much until you realise how easy it is to slip up and destroy something important by accident - don't tempt fate by executing all of your commands with superuser privileges.

Computers make very fast, very accurate mistakes

Actually, this is kind of an important point. Software bugs are pretty common in computer-land, and accidentally wiping your entire hard drive is as easy as trying to run a game in Steam (which contained a misconfigured shell script that ran rm -rf / on your main OS disk when it was configured incorrectly). This isn't a unique occurrence, either - in fact, Red Hat recently had a similar issue with Squid that caused several testers' hard drives to be wiped, too.

So, what's my point? Well, just like everyone else, programmers are fallible too - and sometimes mistakes make their way into production code. Save yourself the hassle of accidentally breaking everything and just run applications as a standard user with restricted permissions. Otherwise you run the risk of deleting important stuff, overwriting vital files, corrupting filesystems, accidentally deleting shared libraries, or a hundred-and-one other things you can do to break your operating system.

People are nasty, too

By running normal userland applications or services as root, you're giving yourself a higher chance of getting stung by malware - for example, if you have ever copied-and-pasted shell commands from the internet, then you might've accidentally executed a malicious command hidden inside the web page. Running standard userland applications with elevated privileges (like a web browser) basically gives malicious software or exploits a free pass to do whatever they please to your computer, without even trying!


Allowing root logins over SSH is a bad idea because it essentially means that if an SSH key is compromised then a malicious user can directly log in with root access on the target machine... which isn't something that's usually a positive experience.

If you disallow root logins over SSH and instead provide power users with sudo privileges, it adds an extra layer of authentication between a malicious user and superuser access by requiring a password to authenticate to superuser. Requiring this extra level of authentication might lessen the consequences of having a compromised user account, and it has an added bonus of increasing accountability - sudo will add entries in the system's auth log whenever someone tries to use sudo to escalate to superuser.

Long story short?

As the old adage goes; With great power comes great responsibility. Using the root account all the time is widely regarded as bad practice, it's insecure for a number of reasons, and it makes the consequences of making a mistake more severe than they need to be.

Treat it with respect, use it sparingly, and give your power users sudo access instead.