Who connected to the server
w
Create new user
RHEL - RedHat, CentOS, Oracle Linux
useradd -g oinstall -G dba,oper,asmadmin,asmdba,asmoper oracle
/usr/sbin/useradd -u 503 -g oinstall -G asmadmin,asmdba,asmoper,dba grid
FTP user (don't allow connect through ssh)
useradd -G ftpgroup newuser -s /sbin/nologin -d /FTP/newuser
passwd newuser
FreeBSD, ftp user (don't allow connect through ssh)
pw adduser newuser -d /FTP/newuser -g 717 -s/bin/sh
passwd newuser
Set password
passwd grid
Change user settings
usermod -aG oinstall -G dba,oper,asmadmin,asmdba,asmoper oracle
FreeDSB: pw usermod username -aG wheel,operator,operator,mail
Check current settings
id oracle
cat /etc/passwd
cat /etc/passwd | grep oracle !! - means that user locked
cat /etc/shadow
Groups
groupadd asmadmin
Ask to change password at next logon
expire
Show account aging information
change -l oracle Last password change, expires, days between change
Password expire
change -E 2016-05-31 oracle on date
passwd -x 90 oracle after 90 days
Disable (lock) user
passwd -l username
Enable (unlock) user
passwd -u username
Remove or drop user
tar -zcvf /nas/backup/account/deleted/v/vivek.$uid.$now.tar.gz /home/vivek/ - replace $uid, $now with actual UID and date/time
# pgrep -u baduser
# ps -fp $(pgrep -u baduser)
# killall -KILL -u baduser
userdel -r vivek
/usr/sbin/userdel baduser
userdel -r baduser - also removes home folder
# find /var/spool/at/ -name "[^.]*" -type f -user baduser -delete - del. at jobs
# crontab -r -u baduser
# lprm baduser - del. print jobs
# find / -user baduser -print - find all files owned by user vivek
# find / -user baduser -exec chown newUserName:newGroupName {} \; - find file owned by a user called vivek and change its ownership as follows
Second root, sudo
useradd -ou 0 -g 0 newuser
passwd newuser
visudo
newuser ALL=(ALL) ALL
newuser ALL=(ALL) NOPASSWD: ALL
To switch root user use
[newuser@server ~]$ sudo su -
vi /etc/pam.d/su
auth sufficient pam_rootok.so add these rows after, if you need su - from newuser user w/o passwd
auth [success=ignore default=1] pam_succeed_if.so user = root
auth sufficient pam_succeed_if.so use_uid user = newuser
id newuser check new settings
grep newuser /etc/passwd
FreeDSB: adduser
FreeDSB: vi /usr/local/etc/sudoers
newuser ALL=(ALL) ALL
Resset root passwd, Boot CD
Boot from Linux CD
Troubleshooting
Rescue a Red Hat Enterprise Linux System
chroot /mnt/sysimage
passwd root
rm -f /.autorelabel
Samba
Show users and their settings
pdbedit -L -v
Reset user password
smbpasswd username