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I want to use a command over ssh:

ssh myuser@myhost mycommand

but doing so I always get: 

sh: mycommand: command not found

using following obviously works: 

ssh myuser@myhost /usr/local/bin/mycommand

and i understand why: it's because the command is somehow executed over a non-login shell.

Using the full command or any other parameters in my ssh command is not an option in my scenario. My command is executed by a script I cannot touch and worked on every host yet except this one.

The host that's giving me the problem is a Synology NAS and the /etc/passwd setting for that myuser is:

myuser:x:1048:100::/var/services/homes/myuser:/bin/sh

Again:

I can:

  • ssh as myuser into myhost
  • execute as myuser using the absolute path provided by which mycommand
  • execute mycommand (non absolute) when already on myhost (via ssh)

I can't but want:

  • execute: ssh myuser@myhost mycommand (non absolute, no additional parameters)
Rui F Ribeiro
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Simon
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2 Answers2

5

Probably, your $PATH doesn't include /usr/local/bin. Since this is ssh, there are three approaches that come to mind:

  1. If PermitUserEnvironment is enabled in the sshd config, you ought to be able to set PATH in ~/.ssh/environment (that's a file in your home directory on the server — the NAS).

  2. If you can edit the sshd config, then you should be able to use SetEnv PATH=/bin:/usr/bin:/usr/local/bin (etc.) to set a path. At least if it's using OpenSSH.

  3. It's possible you could use the ssh client's SetEnv option to send the server a PATH, depending on the server config. You could set this in your ~/.ssh/config file, on your client machine.

Note that both OpenSSH server and client config files can have options limited to particular clients/servers. For example, in the client config, you could do something like this:

Host myhost
    SetEnv PATH=/bin:/usr/bin:/usr/local/bin

to only do that for one server. Note that block continues until the next block starts (e.g, another Host … block) — the indenting is just for visual clarity.

OpenSSH config files are documented in the ssh_config and sshd_config manual pages.

derobert
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  • Thank you for your very detailed answer! Especially 1 and 2 look very promissing. I should have mentioned that I have root rights on host and can edit whatever I want. I guess that for 1 I need to set the enviroment for each user on host. I'll give it a test in a few hours when I'm back in the network. – Simon Jan 08 '19 at 20:39
  • @Simon #2 is a system-wide one, so if you need it for a bunch of users, that's probably the option you want to pick. At least if you can edit the config (no idea what Synology allows). – derobert Jan 08 '19 at 20:59
  • thanks again for your answer, I started to investigate the reason why I even have this problem to begin with and I decided to go another, more simplier but maybe also dirtier (?) way. (see my answer) – Simon Jan 09 '19 at 09:42
  • FYI using ~/.ssh/environment doesn't work for me at all. If I set PATH=$PATH:... and try $ ssh host 'echo $PATH', it prints a literal $PATH (and anything else results in command not found). Explanation here. (Both client and host are Debian FWIW.) – Ryan Lue Nov 03 '20 at 09:34
  • If you go with option (2), remember you have to restart the ssh service (i.e. sudo systemctl restart ssh.service) – Peter Ilfrich Nov 12 '23 at 21:03
4

Ok so on further investigation I noticed that on all of my other hosts mycommand is indeed in /usr/bin not in /usr/local/bin. The reason for this is, that every package manager has installed it in /usr/bin except for the weird "software store" (or whatever it is called) from synology.

I went the "dirty" way and just created a symlink: /usr/bin/mycommand > /usr/local/bin/mycommand:

ln -s /usr/local/bin/mycommand /usr/bin/mycommand

Now for everyone facing a similar problem: there is a reason why a /usr/local/bin exists and there might be risks with my solution. But it's the easiest and fastest and I already spent way to much time on this problem. In my situation all ssh-keys will be limited anyways to one command only so I don't really care.

Anyways: if you want to read more about the difference between those two locations I recommend this post: https://askubuntu.com/a/308048

Simon
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