Debian 11 Bullseye
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Initial Settings : Configure Sudo
2021/08/17
 
Configure Sudo to separate users' duty if some people share privileges.
[1] Install Sudo.
root@dlp:~#
apt -y install sudo

[2] Transfer root privilege to a user all.
root@dlp:~#
# add to the end : user [bullseye] can use all root privilege

# how to write ⇒ destination host=(owner) command

bullseye    ALL=(ALL:ALL) ALL

# push [Ctrl + x] key to quit visudo
# verify with user [bullseye]

bullseye@dlp:~$
/usr/sbin/reboot

Failed to set wall message, ignoring: Access denied
Failed to reboot system via logind: Access denied
Failed to open initctl fifo: Permission denied
Failed to talk to init daemon.
# denied

bullseye@dlp:~$
sudo /usr/sbin/reboot


We trust you have received the usual lecture from the local System
Administrator. It usually boils down to these three things:

    #1) Respect the privacy of others.
    #2) Think before you type.
    #3) With great power comes great responsibility.

[sudo] password for bullseye:   # bullseye's password
.....
.....
# possible execute
[3] In addition to the setting [1], set that some commands are not allowed.
root@dlp:~#
# add aliase for the kind of shutdown commands

# Cmnd alias specification
Cmnd_Alias SHUTDOWN = /usr/sbin/halt, /usr/sbin/shutdown, \
/usr/sbin/poweroff, /usr/sbin/reboot, /usr/sbin/init, /usr/bin/systemctl 

# add ( commands in aliase [SHUTDOWN] are not allowed )
bullseye    ALL=(ALL:ALL) ALL, !SHUTDOWN

# verify with user [bullseye]

bullseye@dlp:~$
sudo /usr/sbin/reboot

[sudo] password for bullseye:
Sorry, user bullseye is not allowed to execute '/usr/sbin/reboot' as root on dlp.srv.world.  
# 拒否された
[4] Transfer some commands with root privilege to users in a group.
root@dlp:~#
# add aliase for the kind of user management commands

# Cmnd alias specification
Cmnd_Alias USERMGR = /usr/sbin/adduser, /usr/sbin/useradd, /usr/sbin/newusers, \
/usr/sbin/deluser, /usr/sbin/userdel, /usr/sbin/usermod, /usr/bin/passwd

# add to the end
%usermgr   ALL=(ALL:ALL) USERMGR

root@dlp:~#
groupadd usermgr

root@dlp:~#
usermod -G usermgr bullseye
# verify with user [bullseye]

bullseye@dlp:~$
sudo /usr/sbin/useradd testuser

bullseye@dlp:~$
bullseye@dlp:~$
sudo /usr/bin/passwd testuser

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully
# possible execute
[5] Transfer some specific commands with root privilege to a user.
root@dlp:~#
# add to the end : set specific commands to each user

fedora   ALL=(ALL:ALL) /usr/sbin/visudo
debian   ALL=(ALL:ALL) /usr/sbin/adduser, /usr/sbin/useradd, /usr/sbin/newusers, \
                       /usr/sbin/deluser, /usr/sbin/userdel, /usr/sbin/usermod, /usr/bin/passwd
ubuntu   ALL=(ALL:ALL) /usr/bin/vim

# verify with user [fedora]

fedora@dlp:~$
sudo /usr/sbin/visudo
# possible open and edit

## Sudoers allows particular users to run various commands as
## the root user, without needing the root password.
##
# verify with user [debian]

debian@dlp:~$
sudo /usr/sbin/userdel -r testuser

debian@dlp:~$    
# possible execute
# verify with user [ubuntu]

ubuntu@dlp:~$
sudo /usr/bin/vim /root/.profile
# possible open and edit

# ~/.profile: executed by Bourne-compatible login shells.
[6] It's possible to display Sudo logs on Journald ( with [journalctl] command ) or Rsyslogd ( in [/var/log/auth.log] file ), however, if you'd like to keep only Sudo logs in another file, Configure like follows.
root@dlp:~#
# add to the end

Defaults syslog=local1
root@dlp:~#
vi /etc/rsyslog.conf
# line 61 : add

local1.*                        /var/log/sudo.log
auth,authpriv.*;local1.none     /var/log/auth.log
*.*;auth,authpriv.none          -/var/log/syslog

root@dlp:~#
systemctl restart rsyslog
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