ssh and sudo

kutty_prasad · 05-05-2008, 01:24 AM

Hi All,

I have sudo access on few machines and I need to perform few things as root user. My question is, how can I remotely execute sudo via ssh. Below is an example:

ssh remote1.host.com "cat filename" <--This works fine.

ssh remote1.host.com "sudo echo newline >> filename" <-- trouble. Permision denied error.

Is there any option to fix this?

Thanks,
Prasad.

Brian1 · 05-05-2008, 07:43 AM

Does using sudo require the use of a password?
Is echo one of the commands that can be done with sudo or are all commands allowed through sudo?

Brian

harsshal · 05-05-2008, 07:55 AM

how are you logged in your machine?
"ssh server.com" by default logs in with the account with which you are logged in.If you are logged in as "user1" it would be user1@server.com.So are you logged in as superdoer while doing ssh?

kutty_prasad · 05-06-2008, 11:48 PM

For Brain1: Yes, sudo will ask me for password and it allows me to use all the commands.

For Harsshal: I login as normal, since I don't have root password, I have to use sudo.

Thanks.

danboland · 05-07-2008, 12:10 PM

i've never had to chain commands over ssh. Ussually i just put them in a shell script and run that through ssh,

like create a file called commands.sh with this:

Code:

#!/bin/sh
sudo echo newline >> filename

and then run that through ssh:
ssh remote1.host.com "commands.sh"

Also, make sure there is no restrictions set up for this sue in the sudousers file

chrism01 · 05-07-2008, 08:13 PM

If sudo expects a passwd (the normal arrangement), then you'll have to supply it somehow.
If you need to automate this, then create a remote script as per danboland, and research the 'expect' tool, which is designed to handle situations like this.
Of course this'll mean storing the clear-text passwd on the remote box; possibly not a good idea...

danboland · 05-08-2008, 03:58 PM

Actually i just tested something like what you where doing, using sudo:

Code:

dev# ssh dan@host.com "sudo ls -l /root/"
dan@host.com's password:
Password:*********

as you can see it asked for my password twice, once for the ssh and once for the sudo. (the sudo was in plain text on teh screen which is very bad...)

But the issue is probably not the ssh and sudo command them selfs then since that is working.

So then i tried to do:

Code:

dev# ssh dan@host.com "sudo echo newline > filename"
dan@host.com's password:
Password:*********

and it created the file in my local directory call 'filename' with the text "newline"

However the file was owned by me, and root like it should of been, so then i did this:

Code:

dev# ssh -dan@host.com "sudo sh -c echo newline2 > /root/filename"
dan@host.com's password:
bash: /root/filename: Permission denied

as you can see, got your error. after reading the sudo man pages i see that if you want to do file redirection you have to do sudo a little differently and i came up with this command:

Code:

dev# ssh dan@host.com "sudo sh -c 'echo newline > /root/filename'"
dan@host.com's password:
Password:*******

This created the file in the root directory, as owned by root.

Dan

kutty_prasad · 05-13-2008, 03:46 AM

Thanks a lot Dan.

I'll try out this method when I get a chance again.

Thanks,