Wipe a hard disk

1) Create a backup:- dd if=/dev/sdax of = /tmp/backup.img 2) To wipe dd if/=/dev/urandom of=/dev/[partition-to-wipe]

How to extract *.xz files ?

How to extract *.xz files ?

If you are running Ubuntu, you should have the xz-utils installed by default. I am running Ubuntu 10.04, and to extract .xz files, I use the following command:

if it is not installed , install by giving the command:- sudo apt-get install xz-utils


xz -d path/to/file.xz

This will extract the file to the current directory.

How to create symbolic links graphically

soln:- press CTRL +SHIFT & Drag

Do not show known users in login window ?
How to remove gdm users list ?


Method 1:

sudo gconf-editor






Method 2:-


sudo -u gdm gconftool-2 --set --type boolean /apps/gdm/simple-greeter/disable_user_list true

Malayalam oin linux

allows access to the system by the user root only

PAM NOLOGIN:-

* allows access to the system by the user root only
* obviates the need to shut down services

* displays the contents of /etc/nologin file

sample content of this file :-

CURRENTLY WE ARE UNDERGOING SYSTEM MAINTENANCE, EXPECT US BACK IN 1600 HOURS

add the following directive

auth required pam_nologin.so to the relevant pam file.
(ex:- for ssh /etc/pam.d/sshd file)


[root@BACKUP-SERVER ~]# find / -name pam_nologin.so
/lib64/security/pam_nologin.so
/lib/security/pam_nologin.so

How will you implement account lockout policy in linux?

How will you implement account lockout policy in linux?

soln:-

PAM_TALLY

* ability to tally failed login attempts and take actions
* Denies user access to the system based on no: of failed login attempts
* This feature / module not enabled by default
* uses /var/log/faillog - logs failed logins
* manipulate failed login counters


which pam_tally ?

/usr/sbin/pam_tally (i.e it is a root enabled utility)


* pam_tally --user username :- displays the count of the username


resetting a failed login counter:-

pam_tally --reset=n --user=username

Add the following line to /etc/pam.d/common-auth

auth required pam_tally.so deny=3 unlock_time=1800

NB:- tested in centos -5.5

for ubuntu systems see:- http://blog.bodhizazen.net/linux/ubuntu-how-to-faillog/