README.md

This bug fix prepends the path of the Singularity installation directory
to the PATH environment variable immediately following installation
using the naked-singularity.sh install command and the final check to
determine if Singularity was installed successfully. The problem here is
that not all secure_path in /etc/sudoers may include the Singualrity
install directory by default, which can lead this final install test to
fail erroneously.

This issue was observed when recently testing the naked-singularity.sh
install command on CentOS 7 and CentOS 8. Both install processes threw a
'Singularity installation failed!' error even though the installations
were successful [1] [2]. No such issue was observed on Ubuntu-based
installations [3]. As stated above, the difference in behavior between
these OSes was tracked down to what default paths were included in the
secure_path variable in the /etc/sudoers file [4] [5] [6].

[1]

...
 INSTALL CNI PLUGIN /usr/local/libexec/singularity/cni/tuning
 INSTALL CNI CONFIGURATION FILES
 DONE
make: Leaving directory `/tmp/singularity/builddir'
Checking if Singularity was installed successully ...
./naked-singularity.sh: line 200: singularity: command not found
ERROR :: Singularity installation failed!
ERROR :: Failed to run install command.
[centos@singularity-centos7-builder naked-singularity]$ singularity --version
singularity version 3.5.3
[centos@singularity-centos7-builder naked-singularity]$ which singularity
/usr/local/bin/singularity
[centos@singularity-centos7-builder naked-singularity]$

[2]

...
INSTALL CNI PLUGIN /usr/local/libexec/singularity/cni/tuning
 INSTALL CNI CONFIGURATION FILES
 DONE
make: Leaving directory '/tmp/singularity/builddir'
Checking if Singularity was installed successully ...
./naked-singularity.sh: line 200: singularity: command not found
ERROR :: Singularity installation failed!
ERROR :: Failed to run install command.
[centos@singularity-centos8-builder naked-singularity]$ singularity --version
singularity version 3.5.3
[centos@singularity-centos8-builder naked-singularity]$ which singularity
/usr/local/bin/singularity
[centos@singularity-centos8-builder naked-singularity]$

[3]

...
 INSTALL CNI PLUGIN /usr/local/libexec/singularity/cni/tuning
 INSTALL CNI CONFIGURATION FILES
 DONE
make: Leaving directory '/tmp/singularity/builddir'
Checking if Singularity was installed successully ...
singularity version 3.5.3
Singularity was installed successfully!
ubuntu@singularity-ubuntu1804-builder:~/naked-singularity$ singularity --versionsingularity version 3.5.3
ubuntu@singularity-ubuntu1804-builder:~/naked-singularity$ which singularity
/usr/local/bin/singularity
ubuntu@singularity-ubuntu1804-builder:~/naked-singularity$

[4]

[centos@singularity-centos7-builder naked-singularity]$ sudo cat /etc/sudoers | grep secure_path
Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin
[centos@singularity-centos7-builder naked-singularity]$

[5]

[centos@singularity-centos8-builder naked-singularity]$ sudo cat /etc/sudoers | grep secure_path
Defaults    secure_path = /sbin:/bin:/usr/sbin:/usr/bin
[centos@singularity-centos8-builder naked-singularity]$

[6]

ubuntu@singularity-ubuntu1804-builder:~/naked-singularity$ sudo cat /etc/sudoers | grep secure_path
Defaults	secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"
ubuntu@singularity-ubuntu1804-builder:~/naked-singularity$