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What's a good way of running a shell script as a different user. I'm using Debian etch, and I know which user I want to impersonate.
If I was doing it manually, I would do:
su postgres
./backup_db.sh /tmp/test
exit
Since I want to automate the process, I need a way to run backup_db.sh as postgres (inheriting the environment, etc)
Thanks!
To run your script as another user as one command, run:
/bin/su -c "/path/to/backup_db.sh /tmp/test" - postgres
Breaking it down:
/bin/su : switch user
-c "/path/to..." : command to run
- : option to su, make it a login session (source profile for the user)
postgres : user to become
I recommend always using full paths in scripts like this - you can't always guarantee that you'll be in the right directory when you su (maybe someone changed the homedir on you, who knows). I also always use the full path to su (/bin/su) because I'm paranoid. It's possible someone can edit your path and cause you to use a compromised version of su.
- (or --login) together with --command, -c doesn't actually start a login session, because -c always forces a non-login shell.
May 1, 2013 at 13:46
- postgress should appear at the end of the command. From the man page: When - is used, it must be specified before any username. For portability it is recommended to use it as last option, before any username. The other forms (-l and --login) do not have this restriction.
If the target user to run has nologin shelll defined, then you can use the -s option to specify the shell:
/bin/su -s /bin/bash -c '/path/to/your/script' testuser
See the following question: run script as user who has nologin shell
To automate this on a schedule you could put it in the user's crontab. Cron jobs won't get the full environment though, but it it might be better to put all the env variables you need in the script itself anyways.
To edit the user's crontab:
sudo crontab -u postgres -e
This should be an informative read -- setuid on shell scripts
If you run su with a "- username" argument sequence, it will make a login shell for the user to give the same environment as the user. Usually, used to quickly execute your script with your home environment from a different login.
Try the su manpage:
su -c script_run_as_postgres.sh - postgres
Alernately, you could use sudo to allow you to run just that comman as postgres without a password. It takes some setup in your /etc/sudoers, though.
The "su -c ... " method posted by others is a good one. For automation, you could add the script to the crontab of the user you need it to execute as.
You can also use:
sudo -u postgres script_run_as_postgres.sh
If the user already has an entry to sudo and you don't know superuser's password then you can try following: This one restarts the postgres initialized at /data/my-db/pgsql/9.6/data
sudo su - postgres -c "/usr/pgsql-9.6/bin/pg_ctl -D /data/my-db/pgsql/9.6/data -l /var/log/pgsql.log restart"
