Having a problem understanding sudo and setting environmental variables

pwjohnston · 05-05-2020, 01:19 PM

Hello,

I'm having difficulty understanding sudo and environmental variables.

I'm currently setting up vagrant on a host so I can play with adding and removing linux VMs and try and learn Linux better. Host is CentOS 7.

When I run

Code:

$ sudo vagrant up

boxes are stored in

Code:

# ll /root/.vagrant.d/boxes
total 0
drwxr-xr-x. 3 root root 37 May  5 13:40 minimal-VAGRANTSLASH-centos7

The problem with this, however, is I only have 25 GB on that partition.

Code:

$ df -h /
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   25G   11G   14G  45% /

I have set up var to store data

Code:

$df -h /var
Filesystem                               Size  Used Avail Use% Mounted on
/dev/mapper/vg--1tb--mirror-var--mirror  197G   43G  145G  23% /var

Per this post I found that I can set the environmental variable for vagrant to put the Vagrant boxes somewhere else.
https://stackoverflow.com/questions/...he-home-folder

Code:

export VAGRANT_HOME=/path/to/vagrant

So I did

Code:

# cp -r ./.vagrant.d/ /var

then deleted the box file from
/root/.vagrant.d/boxes

and

Code:

$ export VAGRANT_HOME=/var/.vagrant.d

run

Code:

$ sudo vagrant up

and the box is still saved in
/root/.vagrant.d/boxes

So I'm thinking maybe sudo runs a command as root and not just with root permission? I do the same process over again

Code:

$su -
# vi ~/.bash_profile 
add the line
export VAGRANT_HOME=/var/.vagrant.d
# cat ~/.bash_profile | grep VAGRANT
export VAGRANT_HOME=/var/.vagrant.d/

# source ~/.bash_profile

drop back into my user profile

Code:

$ sudo vagrant up

boxes are still being saved to

Code:

$ sudo ls -lah /root/.vagrant.d/boxes
[sudo] password for langenoir: 
total 0
drwxr-xr-x. 3 root root  42 May  5 14:07 .
drwxr-xr-x. 7 root root 119 May  5 14:07 ..
drwxr-xr-x. 3 root root  37 May  5 14:07 minimal-VAGRANTSLASH-centos7

I really don't understand what is going on here. I keep reading that sudo elevates user permissions. I thought that means it gives my user root permissions temporarily to run a command. I'm guessing that is wrong.

shruggy · 05-05-2020, 01:39 PM

By default, sudo retains only a few select variables from the user environment. To change this, see
1) the sudo option -E / --preserve-env;
2) description of the env_keep setting in sudoers(5).

Turbocapitalist · 05-05-2020, 01:42 PM

Close. sudo runs the designated command as another user entirely for the duration of that command. If no use is designated at runtime then the default is root. You'll want to look more closely at some of the options you pass to sudo, such as --preserve-env or --preserve-env=... where ... is the list of variables to pass over to the new user. You may have to edit /etc/sudoers to list the variables allowed.

Code:

...
Defaults        env_keep+="FOO"
Defaults        env_keep+="BAR"
...

pwjohnston · 05-05-2020, 02:46 PM

That -E environment option seems to be what I was missing.

Code:

$ printenv | grep VAGRANT
VAGRANT_HOME=/var/.vagrant.d/

$ sudo -E vagrant up

$ ls -lah /var/.vagrant.d/boxes/
total 12K
drwxr-xr-x. 3 root root 4.0K May  5 15:40 .
drwxrwxrwx. 7 root root 4.0K May  5 15:39 ..
drwxr-xr-x. 3 root root 4.0K May  5 15:40 minimal-VAGRANTSLASH-centos7

Thank you shruggy and Turbocapitalist.