Adding script to rc.local

NotionCommotion · 06-09-2017, 06:11 AM

How come I can execute /usr/local/bin/mytunnel.sh (script shown below) directly from the cli and it will spawn a ssh socket process, yet adding /usr/local/bin/tempaccess.sh to /etc/rc.local will not?

Code:

#!/bin/sh
ip=12.34.567.89
while [ true ] ;
do
    if [ $(ss dst $ip | grep -q '$ip:ssh') ]
    then
        sleep 4
    else
        #Note that following is a blocking command given server configuration
        ssh -R 2220:localhost:22 myuser@$ip
    fi
done

wpeckham · 06-09-2017, 06:19 AM

Quote:

Originally Posted by NotionCommotion

How come I can execute /usr/local/bin/mytunnel.sh (script shown below) directly from the cli and it will spawn a ssh socket process, yet adding /usr/local/bin/tempaccess.sh to /etc/rc.local will not?

Code:

#!/bin/sh
ip=12.34.567.89
while [ true ] ;
do
    if [ $(ss dst $ip | grep -q '$ip:ssh') ]
    then
        sleep 4
    else
        #Note that following is a blocking command given server configuration
        ssh -R 2220:localhost:22 myuser@$ip
    fi
done

There could be many possible reasons, but for one you have set no path. Since anything run from the rc.local runs as root but before any logon, the path is not set. You must either call each external executable using the full path name or set a path variable that contains all of the paths to the different executables you will call.

For another, the rc.local is NOT executable by default on most modern distributions. If you are going to modify it to call another script, make sure that both scripts are executable. (permission 755 will do, or 500 if you want it to be secure, I use 750 on mine for convenience)

NotionCommotion · 06-09-2017, 09:05 AM

Thanks wpeckham,

Yeah, multiple reasons!

Not path as they were being resolved.

Didn't have pki keys for root, only my normal user.

kakistocrat · 06-09-2017, 09:49 AM

If you want it to reconnect automatically you can put the SSH client itself inside a loop:

Code:

while ! ssh -o ServerAliveInterval=20 -i ./some.key.rsa -R 2220:localhost:22 myuser@$ip; do sleep 2; done;

Also, pretty much all of those options could be stored in ~/.ssh/config to make it shorter. Put it in at the top of the configuration file.

Code:

Host myshortcut
        HostName 203.0.113.111
        User myuser
        IdentityFile /home/me/some.key.rsa
        ServerAliveInterval 20
        RemoteForward localhost:2220 localhost:22

So to use that, it'd be the following:

Code:

while ! ssh myshortcut; do sleep 2; done;

See "man ssh_config" for all the options.

jpollard · 06-10-2017, 08:32 PM

Quote:

Originally Posted by NotionCommotion

How come I can execute /usr/local/bin/mytunnel.sh (script shown below) directly from the cli and it will spawn a ssh socket process, yet adding /usr/local/bin/tempaccess.sh to /etc/rc.local will not?

Code:

#!/bin/sh
ip=12.34.567.89
while [ true ] ;
do
    if [ $(ss dst $ip | grep -q '$ip:ssh') ]
    then
        sleep 4
    else
        #Note that following is a blocking command given server configuration
        ssh -R 2220:localhost:22 myuser@$ip
    fi
done

If your distribution is using systemd, verify that "NetworkManager-wait-online" is enabled.

One way for the failure to occur is that the network is not yet ready when rc.local is run.

wpeckham · 06-11-2017, 07:45 AM

Another good idea is to trap and redirect the STDOUT and STDERR to a couple of files so you can READ them and see what messages they log.
That might look something like

Code:

/usr/local/bin/mytunnel.sh >/tmp/mytun.out 2>/tmp/mytun.err

jpollard · 06-11-2017, 08:00 AM

Systemd is SUPPOSED to catch all the error messages and log them.
:-)