Check to see if a script was run as root

 in

If you need to make sure a script is run as root, add the following to the start of the script:

  if [[ $UID -ne 0 ]]; then
    echo "$0 must be run as root"
    exit 1
  fi

______________________

Mitch Frazier is an Associate Editor for Linux Journal.

Comments

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.

I don't belive this is the

Anonymous's picture

I don't belive this is the right way of checking the user. This is as easy as your solution but is harder to bypass.

to bypass your code:

$ sh
$ export UID=0

run command

better way:


LUID=$(id -u)
if [[ $LUID -ne 0 ]]; then
echo "$0 must be run as root"
exit 1
fi

hope this help
bye

Not a problem, at least with bash

Mitch Frazier's picture

Bash won't let you do "export UID=0", UID is a read-only variable.

Mitch Frazier is an Associate Editor for Linux Journal.

Effective User ID

lowkey's picture

You may find it more useful to check for the Effective User ID (EUID) rather than the plain User ID (UID). Then your script will work with SUID cases.

Just replace $UID with $EUID in the above snippet.

Maybe

Mitch Frazier's picture

As I recall the set-uid bit doesn't work on shell scripts, so unless your script is going to be run by a compiled program that has the set-uid bit set this wouldn't make any difference. Or am I missing something here?

Mitch Frazier is an Associate Editor for Linux Journal.

bash != sh

Anonymous's picture


$ sudo sh -c 'set' | grep UID
SUDO_UID='1000'
$ sudo bash -c 'set' | grep UID
EUID=0
SUDO_UID=1000
UID=0

bash provides the environment variable 'UID', but other shells do not. Additionally '[[', while not bash specific is not present in all shells. A better solution (albeit, one dependent on 'id'):


uid=`id -u` && [ "$uid" = "0" ] ||
{ echo "must be root"; exit 1; }

Whose id command?

charliebrady's picture

A little safer/more reliable to do:

uid=$(/usr/bin/id -u) && [ "$uid" = "0" ] ||
{ echo "must be root"; exit 1; }

Use #!/bin/bash

Mitch Frazier's picture

I always put "#!/bin/bash" at the top of my scripts, but beyond that I don't worry about non-bash environments. However, there certainly are some scripts that may run or need to run in an environment where bash does not exist.

Mitch Frazier is an Associate Editor for Linux Journal.

Webcast
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers

Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.

Learn More

Sponsored by AMD

White Paper
Red Hat White Paper: Using an Open Source Framework to Catch the Bad Guy

Built-in forensics, incident response, and security with Red Hat Enterprise Linux 6

Every security policy provides guidance and requirements for ensuring adequate protection of information and data, as well as high-level technical and administrative security requirements for a system in a given environment. Traditionally, providing security for a system focuses on the confidentiality of the information on it. However, protecting the data integrity and system and data availability is just as important. For example, when processing United States intelligence information, there are three attributes that require protection: confidentiality, integrity, and availability.

Learn more about catching the bad guy in this free white paper.

Learn More

Sponsored by DLT Solutions