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LFCS_Module2_UserandGroupManagement Cheat Sheet by

Creating Users, Groups

useradd -s /bin/zsh -c 'my user' -m anna
Create user anna with default shell (-s) and home dir (-m)
id user
Show user info
groupadd sales
Create 'sales' group
usermod -aG sales anna
Add anna to supple­mentary group 'sales'
useradd -D
Display default value of user
Config­uration file for default value
Additional config­uration value
Content in skel will be copied to new user home dir
lid -g groupname
List all users that are members of a group

Resource Access Restri­ctions

yum groups install 'Directory Client'
Install the Utility
yum install authco­nfi­g-gtk
Install graphic interface of auth
Limit config­uration file:n­proc, hard limit, soft limit

Access Control List

setfacl -R -m d:g:sa­les:rx account
Set ACL so 'sales' group can read, execute on account dir and all sub-dir on default
Display all access control list permis­sions (+ symbol)

System­-Wide Enviro­nment Profile

env (environment variable)
export var (store variable)
unset var (reset variable)
env -i bash (change environment)

vim /etc/environment (set new variable)
source /etc/environement (source new variable w/o reboot)

Manage Template User Enviro­nment

vim /etc/skel/.bashrc (file for setting)
/etc/skel (putting new file here will make it default for new user only)


4, Read on File, Ls on Di
2, Modify on File, Create/Del on Dir
1, Run on File, Cd into Dir
chgrp account account
Change group owner of account dir to 'account' group
chown anna account
Change anna to owner of 'account' dir
chown linda.s­ales sales
Change user and group owner of 'sales' dir to linda, sales
chmod g+w account
Make members of 'account' group have write permis­sions on account dir
chmod 770 sales
Make user, group have read, write, execute permis­sion; others none

Extended Attributes

chattr +i file1
Make file1 has "­imm­uta­ble­" attribute

Managing Quota on Ext4

yum install -y quota
Install quota package
vim /etc/fstab
Config file for mounting file system automa­tically
mount -o remount /quota
Make sure the file system mounted with right options
quotacheck -mavug
Scan the file system
quota -vu lisa
Display quota on user lisa
quotaon -a
Activating quota
edquota -u lisa
Edit quota limit on user lisa; soft to 10; hard to 10
edquota -b lisa linda
Copy the quota limit from lisa to linda
dd if=/de­v/zero of=/qu­ota­/bi­gfile bs=1M count=3
if input file; of output file; bs block size; write 3 times
repquota -aug
Display quota overview

Password Properties

echo password | passwd -stdin brenda
Echo password to change brenda's password
chage brenda
Intera­ctive change

User,Group Config­uration File

cat /etc/group
Group config file
cat /etc/p­asswd
User config file
cat /etc/s­hadow
User Config file
vipw -s
vi passwd consis­tently

Advanced Permis­sions

4; run as owner on file
2; run as group owner on file; inherit dir group owner
1; delete only if owner on dir
chmod u+s playme
Set UserID bit on playme
chmod g+s *
Set GroupID bit on *
chmod +t *
Apply StickyBit, other users cannot delete file created by owner

Finding files w/ special permis­sions

find -perm 0600
Find file with read,write for users only
find / -perm /4000 -exec ls -l {} \;
Find files in root dir with userID bit and list it

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