How to write a shell script that runs some commands as superuser and some commands not as superuser, without having to babysit it?
UnixSudoUnix Problem Overview
I want to write a shell script to automate a series of commands. The problem is some commands MUST be run as superuser and some commands MUST NOT be run as superuser. What I have done so far is something like this:
#!/bin/bash
command1
sudo command2
command3
sudo command4
The problem is, this means somebody has to wait until command1 finishes before they are prompted for a password, then, if command3 takes long enough, they will then have to wait for command3 to finish. It would be nice if the person could get up and walk away, then come back an hour later and be done. For example, the following script has this problem:
#!/bin/bash
sleep 310
sudo echo "Hi, I'm root"
sleep 310
sudo echo "I'm still root?"
How can I make it so that the user can just enter their password once, at the very start, and then walk away?
Update:
Thanks for the responses. I'm running on Mac OS X Lion and ran Stephen P's script and got different results: (I also added $HOME)
pair@abbey scratch$ ./test2.sh
uid is 501
user is pair
username is
home directory is /Users/pair
pair@abbey scratch$ sudo ./test2.sh
Password:
uid is 0
user is root
username is root
home directory is /Users/pair
Unix Solutions
Solution 1 - Unix
File sutest
#!/bin/bash
echo "uid is ${UID}"
echo "user is ${USER}"
echo "username is ${USERNAME}"
run it: `./sutest' gives me
uid is 500
user is stephenp
username is stephenp
but using sudo: sudo ./sutest
gives
uid is 0
user is root
username is stephenp
So you retain the original user name in $USERNAME when running as sudo. This leads to a solution similar to what others posted:
#!/bin/bash
sudo -u ${USERNAME} normal_command_1
root_command_1
root_command_2
sudo -u ${USERNAME} normal_command_2
# etc.
Just sudo to invoke your script in the first place, it will prompt for the password once.
I originally wrote this answer on Linux, which does have some differences with OS X
OS X (I'm testing this on Mountain Lion 10.8.3) has an environment variable SUDO_USER
when you're running sudo, which can be used in place of USERNAME
above, or to be more cross-platform the script could check to see if SUDO_USER is set and use it if so, or use USERNAME if that's set.
Changing the original script for OS X, it becomes...
#!/bin/bash
sudo -u ${SUDO_USER} normal_command_1
root_command_1
root_command_2
sudo -u ${SUDO_USER} normal_command_2
# etc.
A first stab at making it cross-platform could be...
#!/bin/bash
#
# set "THE_USER" to SUDO_USER if that's set,
# else set it to USERNAME if THAT is set,
# else set it to the string "unknown"
# should probably then test to see if it's "unknown"
#
THE_USER=${SUDO_USER:-${USERNAME:-unknown}}
sudo -u ${THE_USER} normal_command_1
root_command_1
root_command_2
sudo -u ${THE_USER} normal_command_2
# etc.
Solution 2 - Unix
You should run your entire script as superuser. If you want to run some command as non-superuser, use "-u" option of sudo:
#!/bin/bash
sudo -u username command1
command2
sudo -u username command3
command4
When running as root, sudo doesn't ask for a password.
Solution 3 - Unix
If you use this, check man sudo
too:
#!/bin/bash
sudo echo "Hi, I'm root"
sudo -u nobody echo "I'm nobody"
sudo -u 1000 touch /test_user
Solution 4 - Unix
Well, you have some options.
You could configure sudo to not prompt for a password. This is not recommended, due to the security risks.
You could write an expect script to read the password and supply it to sudo when required, but that's clunky and fragile.
I would recommend designing the script to run as root and drop its privileges whenever they're not needed. Simply have it sudo -u someotheruser command
for the commands that don't require root.
(If they have to run specifically as the user invoking the script, then you could have the script save the uid and invoke a second script via sudo with the id as an argument, so it knows who to su to..)