How to run a bash command as a different user in Capistrano? - capistrano

Question

How would I accomplish the following in Capistrano?
sudo su - postgres
/usr/pgsql-9.2/bin/pg_ctl status -D /var/lib/pgsql/9.2/data/
The following task doesn't work:
task :postgres_check do
on roles(:db) do in: :sequence |host|
execute "sudo su - postgres << EOF
/usr/pgsql-9.2/bin/pg_ctl status -D /var/lib/pgsql/9.2/data/
EOF"
end
end
The commands in the execute statement works in a bash script.
EDIT 1:
I also tried the following:
task :postgres_check do
on roles(:postgres_pref_db), in: :sequence do |host|
execute "/usr/pgsql-9.2/bin/pg_ctl status -D /var/lib/pgsql/9.2/data", :shell => "sudo su - postgres"
end
end
Which errors with:
DEBUG [68eb95f2] Command: /usr/pgsql-9.2/bin/pg_ctl status -D /var/lib/pgsql/9.2/data
DEBUG [68eb95f2] pg_ctl: could not open PID file "/var/lib/pgsql/9.2/data/postmaster.pid": Permission denied
cap aborted!
SSHKit::Command::Failed: /usr/pgsql-9.2/bin/pg_ctl status -D /var/lib/pgsql/9.2/data stdout: Nothing written
It appears that it still executing the command as the ssh user.

Answer 1

I came across this and explored the answer for myself. I wouldn't have accepted the answer either to I'll provide what I did.
task :copy_files do
on roles(:web) do |host|
as 'other_user' do
execute "whoami"
end
end
end
Capistrano 3 uses SSH KIT and I found these examples really helpful for getting bash commands to work inside my tasks.
https://github.com/capistrano/sshkit/blob/master/EXAMPLES.md
You'll want to checkout ssh kit and see about on(), within(), with(), as() ... they can be used nested in any order. So you end up having a lot of control even if it takes a few minutes to learn.
I think for your specific example you will want to use as() and within() to become the postgres user and run commands within a certain directory.
Also I had to disable requiretty on my /etc/sudoers for my deploy user.