I'm trying to run a command as root (via sudo) on a remote server, and capture stdout (but not stderr) into a file.
eg. Something like this:
ssh user@remote "cat /root/file.tar | gzip" > root-file.tar.gz
Except I need to be root on the remote:
ssh user@remote "sudo cat /root/file.tar | gzip" > root-file.tar.gz
root has no password and can't be logged in as, so I can't use su or ssh root@server.
When I try the above command, I get:
$ ssh user@remote "sudo cat /root/file.tar | gzip" > root-file.tar.gz
sudo: no tty present and no askpass program specified
I added -t so that ssh allocates a tty, but then root-file.tar.gz gets the output from sudo (and gzip, but I can –force), so I guess it's capturing remote stdout and stderr into local stdout:
$ ssh -t user@remote "sudo cat /root/file.tar | gzip" > root-file.tar.gz
(hangs)
$ cat root-file.tar.gz
gzip: compressed data not written to a terminal. Use -f to force compression.
For help, type: gzip -h
[sudo] password for user:
I've white-listed specific commands using NOPASSWD in sudoers, which works well for regularly-occurring scripts, but I find that I want to do this sort of thing occasionally with different arbitrary commands so I can't be forever adding NOPASSWD.
Best Answer
You can pass the -S option[0] to sudo, so it can accept the password from stdin instead of requiring a tty.
This will probably cause your password to echo to the terminal, so try turning echo off yourself:
[0] From the manpage: The ‑S (stdin) option causes sudo to read the password from the standard input instead of the terminal device. The password must be followed by a newline character.