Tukukkk

I'm running Ubuntu (version 1804.2018.817.0) from the Window Store on top of Windows 10 (version 1803 build 17134.345) using the Window Subsystem for Linux.

When I first open the console I'm logged in with the account I created when I first ran Ubuntu. In this context I can execute things in the Windows path like cmd.exe.

However, when I switch to root using sudo su -, the $PATH variable no longer contains the Windows path information. So when I type cmd.exe it says cmd.exe: command not found.

My questions are:

1. Where do the Window $PATH values come from when I first open Ubuntu?


2. Why doesn't the root user get the Windows $PATH values when I use sudo su -?


3. How can I configure bash so that $PATH contains Window path values when I use sudo su -, so that I can run commands like cmd.exe?

I answer although this topic belongs rather to askubuntu.

1. Where do the Window $PATH values come from when I first open Ubuntu?.
   
   From standard Windows %PATH% environment variable because ubuntu.exe process is a child of conhost.exe (as well as the Windows command prompt cmd.exe).




2. Why doesn't the root user get the Windows $PATH values when I use sudo su -?
   Check sudo sudo -V | grep PATH from wsl prompt. Read man sudo for the explanation:

ENVIRONMENT

     sudo utilizes … environment variables.  The security policy 

     has control over the actual content of the command's environment.

…

     PATH             May be overridden by the security policy.

The default security policy is sudoers, which is configured via
the file /etc/sudoers.

Try this illustrative example (paste following three commands severally into an open cmd command prompt):

wsl echo ${#PATH}

wsl sudo su   -c 'echo ${PATH} ^&^& echo ${#PATH}'

wsl sudo su - -c 'echo ${PATH} ^&^& echo ${#PATH} ^&^& cat /etc/sudoers ^| grep Default'

Result (the latter command takes a look at /etc/sudoers as well):

d:test> wsl echo ${#PATH}

1557



d:test> wsl sudo su   -c 'echo ${PATH} ^&^& echo ${#PATH}'

[sudo] password for user:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games

88



d:test> wsl sudo su - -c 'echo ${PATH} ^&^& echo ${#PATH} ^&^& cat /etc/sudoers ^| grep Default'

[sudo] password for user:

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin

70

Defaults        env_reset

Defaults        mail_badpass

Defaults        secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

Read man sudoers as well for further explanation of Defaults options:

env_reset   If set, sudo will run the command in a minimal environment containing

            the TERM, PATH, HOME, MAIL, SHELL, LOGNAME, USER, USERNAME and SUDO_*

            variables… If the secure_path option is set, its value will be used

            for the PATH environment variable.  This flag is on by default.



secure_path Path used for every command run from sudo.  If you don't trust the people

            running sudo to have a sane PATH environment variable you may want to use

            this.  Another use is if you want to have the “root path” be separate from

            the “user path”.  Users in the group specified by the exempt_group option

            are not affected by secure_path.  This option is not set by default.

3. 
   

   How can I configure bash so that $PATH contains Window path values when I use sudo su -, so that I can run commands like cmd.exe?

   
   
   
   
   
   • You could use env_keep option via sudoedit (not recommended for security reasons) to preserve your user's environment variables.
   
   
   • For swift advance, copy and paste the following into the root prompt. It will add all folder paths from current Windows %path% variable to $PATH. You might consider make it a .sh script and add some advanced logic:
   
   
   
   

cmd.exe /c echo works!            # merely for documentation

echo "${#PATH}"                   # merely for documentation

cmd_path=`/mnt/c/Windows/System32/cmd.exe /C echo "%path:\\=\\\\%"`

OIFS="$IFS"                       # backup $IFS

IFS=';'

read -a c_p_n <<< "${cmd_path}"

IFS="$OIFS"                       # restore $IFS

OPATH="${PATH}"                   # backup  $PATH

for i in "${!c_p_n[@]}"; do PATH=${PATH%/}:$(sed -e 's#^(.):#/mnt/L1#' -e 's#\#/#g' <<< "${c_p_n[$i]}"); done

echo "${#PATH}"                   # merely for documentation

cmd.exe /c echo works!            # merely for documentation

Result:

user@COMP:~$ sudo su -

root@COMP:~# cmd.exe /c echo works!            # merely for documentation

cmd.exe: command not found

root@COMP:~# echo "${#PATH}"                   # merely for documentation

70

root@COMP:~# cmd_path=`/mnt/c/Windows/System32/cmd.exe /C echo "%path:\\=\\\\%"`

root@COMP:~# OIFS="$IFS"                       # backup $IFS

root@COMP:~# IFS=';'

root@COMP:~# read -a c_p_n <<< "${cmd_path}"

root@COMP:~# IFS="$OIFS"                       # restore $IFS

root@COMP:~# OPATH="${PATH}"                   # backup  $PATH

root@COMP:~# for i in "${!c_p_n[@]}"; do PATH=${PATH%/}:$(sed -e 's#^(.):#/mnt/L1#' -e 's#\#/#g' <<< "${c_p_n[$i]}"); done

root@COMP:~# echo "${#PATH}"                   # merely for documentation

1555

root@COMP:~# cmd.exe /c echo works!            # merely for documentation

works!