[Bug]: Linux client uses hardcoded executable locations in /usr

[VladV]

Application

Outline Client

Describe the bug

I installed the AppImage client to an older version of Linux Mint, and it was rather difficult to get the service up.

First I got an error ENOENT "var/run/outline-controller" because the service failed to install.
After tweaking the install script by hand, I got errors "failed to add outline tun network interface" and later "configure system proxy failure".

In all cases it turned out, the culprit was in the hardcoded pathes to the executables – /usr/bin/sed, /usr/sbin/ip, /usr/sbin/sysctl etc.
On my system they are located in /bin and /sbin, without /usr prefix.

I worked around the problem by creating symlinks in the expected places – ln -s /sbin/ip /usr/sbin/ip and so on.
May I suggest that the scripts are changed to use system path instead of hardcoded locations?

Steps to reproduce

Download Appimage from getoutline.org, try to get it running on a system without ip in /usr/sbin folder.

What did you expect to happen?

No response

What actually happened?

No response

Outline Version

1.12

What operation system are you using?

Linux

Operating System Version

No response

Screenshots and Videos

No response

[sbruens]

This is the same as #1488. This will soon be obsolete once the Linux routing rewrite done by @jyyi1 is done.