How can I get the brew installed path in macOS's non-interactive ssh $PATH variable?

[cdayjr]

Trying to use mosh to connect to a macOS installation that has mosh installed via Homebrew results in the following:

$ mosh <host>
zsh:1: command not found: mosh-server
Connection to <host> closed.
/usr/bin/mosh: Did not find mosh server startup message. (Have you installed mosh on your server?)

Upon closer inspection I found that mosh-server was installed in /usr/local/bin:

$ which mosh-server
/usr/local/bin/mosh-server

Getting the $PATH from a bare ssh command returns the following:

$ ssh <host> 'echo $PATH'
/usr/bin:/bin:/usr/sbin:/sbin

If I ssh into the machine, it runs all of the .profile files, etc. and does contain the correct path, but this doesn't happen for mosh or the command above which I assume is because it's a non-interactive connection it doesn't run those scripts.

Interestingly, /etc/paths does contain the correct path:

/usr/local/bin
/usr/bin
/bin
/usr/sbin
/sbin

so somehow the $PATH there gets generated from something else.

I found a workaround by adding a .ssh/environment file that contains the following:

PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin

and adding this line to /etc/ssh/sshd_config and restarting the ssh service:

PermitUserEnvironment yes

This works, but it doesn't seem ideal; apparently there are security concerns with setting PermitUserEnvironment.

Has anyone else ran into this? Is there something that can be done to get that path working correctly, preferably automatically when something like mosh-server that needs it to function correctly is installed?

[the-mgt42]

Thanks, this worked for me, but I agree I'd like a better solution without using PermitUserEnvironment

[carlocab]

This might help: https://superuser.com/questions/1484960/set-path-when-ssh-into-macos

Searching for macos ssh path might also reveal other solutions.

[gromgit]

I assume is because it's a non-interactive connection it doesn't run those scripts

I don't use mosh, but I'm quite sure it creates an interactive connection, else it would be pointless. :)

What ssh does when directly invoking a command on the server is to spawn a interactive non-login shell, so ~/.zprofile will never be sourced. Since you're using zsh, the following paragraph from the STARTUP/SHUTDOWN FILES section of the zsh man page is relevant:

Commands are then read from $ZDOTDIR/.zshenv. If the shell is a login shell, commands are read from /etc/zsh/zprofile and then $ZDOTDIR/.zprofile. Then, if the shell is interactive, commands are read from /etc/zsh/zshrc and then $ZDOTDIR/.zshrc. Finally, if the shell is a login shell, /etc/zsh/zlogin and $ZDOTDIR/.zlogin are read.

So if you want Homebrew stuff to be available no matter when, I think adding:

eval "$(/usr/local/bin/brew shellenv)"

to ~/.zshenv instead of ~/.zprofile would probably be the best solution.

[cdayjr]

Thanks! Adding the following to ~/.zshenv did the trick for me and makes perfect sense.

# Homebrew path support
if command -v /usr/local/bin/brew >/dev/null 2>&1; then
  eval "$(/usr/local/bin/brew shellenv)"
fi

I don't use mosh, but I'm quite sure it creates an interactive connection, else it would be pointless. :)

It does eventually over mosh itself, but it uses SSH initially in a non-interactive way to spawn a mosh connection after that.

Per https://mosh.org/

Same login method.

Mosh doesn't listen on network ports or authenticate users. The mosh client logs in to the server via SSH, and users present the same credentials (e.g., password, public key) as before. Then Mosh runs the mosh-server remotely and connects to it over UDP.

[corneliusroemer]

Note, on ARM macs, the brew prefix has changed from /usr/local to /opt/homebrew, so you need to add:

# Homebrew path support
if command -v /opt/homebrew/bin/brew >/dev/null 2>&1; then
  eval "$(/opt/homebrew/bin/brew shellenv)"
fi

to ~/.zshenv.

[gromgit]

A (fairly) portable chunk of shell code, if you have one set of startup scripts across multiple platforms like me:

homebase=
case "$(uname -sm)" in
  Darwin\ x86_64) homebase=/usr/local;;
  Darwin\ arm64) homebase=/opt/homebrew;;
  Linux\ x86_64) homebase=/home/linuxbrew/.linuxbrew;;
esac
if [[ -z $homebase ]]; then
  echo "NOTE: Homebrew is not supported on this platform" >&2
elif [[ ! -x ${homebase}/bin/brew ]]; then
  echo "NOTE: Homebrew is not installed" >&2
else
  eval "$("${homebase}/bin/brew" shellenv)"
fi

[corneliusroemer]

@gromgit but you need to put that in different files depending on which shell you use. Maybe you could add another script that automatically adds your chunk of code to a variety of startup scripts: .zshenv, .profile etc!

[gromgit]

That's an exercise for the reader. 😀