how to check open port on ubuntu

simply  run this CLI

netstat -anltp | grep "LISTEN"

20 Linux System Monitoring Tools Every SysAdmin Should Know

Click Here guys.. a must know for system admin

vi search

Vi: Search and Replace

Change to normal mode with .

Search (Wraped around at end of file):

  Search STRING forward :   / STRING.
 Search STRING backward:   ? STRING.

 Repeat search:   n
 Repeat search in opposite direction:  N  (SHIFT-n)

Replace: Same as with sed, Replace OLD with NEW:

First occurrence on current line:      :s/OLD/NEW

Globally (all) on current line:        :s/OLD/NEW/g

Between two lines #,#:                 :#,#s/OLD/NEW/g

Every occurrence in file:              :%s/OLD/NEW/g 

How to block port 80 on ubuntu

I just block my port 80 by using this CLI

iptables -A INPUT -j DROP -p tcp --destination-port 80 -i eth0

The code above will drop all tcp packets coming into your Linux computer on device eth0 on port 80. If your Internet connection runs through a device other than eth0, go ahead and make the adjustment.

To remove the iptables rule use the following code:

iptables -D INPUT -j DROP -p tcp --destination-port 80 -i eth0

credit to : foogazi

Install SNMPD on Ubuntu

1.Installation

root@ibsen:~# sudo apt-get install snmpd
Reading package lists... Done
Building dependency tree     
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libmpich1.0gf libdc1394-22 genisoimage linux-headers-2.6.27-7 libgfortran2 dvd+rw-tools linux-headers-2.6.27-7-generic libcarp-clan-perl libxml-xql-perl libparse-yapp-perl
  rdate python-xml localechooser-data gcc-4.2-base libimage-size-perl libdebconfclient0 libvisual-0.4-0 libmyth-python perlmagick libvisual-0.4-plugins libavdevice52
Use 'apt-get autoremove' to remove them.
The following extra packages will be installed:
  libperl5.10 libsensors3 libsnmp-base libsnmp15
Suggested packages:
  lm-sensors
The following NEW packages will be installed:
  libperl5.10 libsensors3 libsnmp-base libsnmp15 snmpd
0 upgraded, 5 newly installed, 0 to remove and 3 not upgraded.
Need to get 2463kB of archives.
After this operation, 7987kB of additional disk space will be used.
Do you want to continue [Y/n]? 

answer y

2. Configuration

Move existing /etc/snmp/snmpd.conf configuration file to /etc/snmp/snmpd.conf.org

mv /etc/snmp/snmpd.conf  /etc/snmp/snmpd.conf.org

Create a new /etc/snmp/snmpd.conf file:

rocommunity  public
syslocation  "PDC, Peters DataCenter"
syscontact  peter@it-slav.net

Make snmpd use the newly created file and make it listen to all interfaces:

Edit /etc/default/snmpd

Change from:

# snmpd options (use syslog, close stdin/out/err).
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1'

To:

# snmpd options (use syslog, close stdin/out/err).
#SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid 127.0.0.1'
SNMPDOPTS='-Lsd -Lf /dev/null -u snmp -I -smux -p /var/run/snmpd.pid -c /etc/snmp/snmpd.conf'

and restart snmpd

/etc/init.d/snmpd restart

Credit to http://www.it-slav.net/blogs/2009/02/05/install-and-configure-snmp-on-ubuntu/

make symbolic link on Unix

# ln -s /usr/home /home or ln -s /data/moodle2/ moodle2

list all installed application on ubuntu

list all installed application on ubuntu

dpkg --get-selections

Centos - Adduser

You can also do this from the command line, below are the equivalent commands. You need to have root level access to use the commands below.

• usr/sbin/useradd [options] login_name
  creates a new user
• usr/sbin/usermod [options] login_name
  modifies a user’s attributes
• usr/sbin/userdel [options] login_name
  deletes the specified user. Use the -r option to automatically remove the user’s home directory and mail spool.
• usr/bin/passwd login_name
  sets the password for the specified user
• usr/sbin/groupadd [options] group_name
  creates a new group
• usr/sbin/groupmod [options] group_name
  modifies a group’s attributes
• usr/sbin/groupdel group_name
  deletes the specified group

Repair table MYSQL

Today i face 1 problem when i want mysqldump my D. my error is

Incorrect key file for table 'mdl_block_instance'; try to repair it

This command to help you to auto-repair your table on mysql

mysqlcheck -uusername -p --auto-repair namedatabase

Mysqldump

this how the usual CLI for mysqldump

mysqldump -u username -p dbname > backupname.sql

restore back from mysql

mysql -u username -p dbname '<' yousqldumpfile.sql

Recently, I was facing problem to restore a UTF8-Enabled database which stores a lot of Arabic text in the db itself.

I have to re-dump back the db by appending the --default-character-set=charset_name option in the dump command :

mysqldump -uroot -p --default-character-set=utf8 --databases yourdbname > yourdumpfile.sql

To restore, again you have to append the same option :

mysql -uroot -p --default-character-set=utf8 '<' youdumpsql.sql ** i need to add '<' because i will become hidden in this blog,if you want tu use the sqldump please to remove ' at '<' on restore CLI.

Thanks

htpasswd tips

to add another user on htpasswd file

htpasswd -s alimdevpass username

Update / Upgrade Ubuntu Server

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade

If the kernel or kernel modules have been updated, you should reboot your computer/server.

No netwrok after clone/copy using VMWare ESX

After making a copy/clone of an ubuntu server 8.10, i face a network problem.

1. "ifconfig" shows no eth0 device, just the 127.0.0.1 loopback
2. "/etc/init.d/networking restart" reports:

SIOCSIFADDR: No such device
eth0: ERROR while getting interface flags: No such device
SIOCSIFNETMASK: No such device
SIOCSIFBRDADDR: No such device
eth0: ERROR while getting interface flags: No such device
Failed to bring up eth0.

Solution
When you create a complete clone/copy of your vmware machine, a new ethernet MAC address is assigned.

follow this step :
as a root
run this CLI

# rm -fr /etc/udev/rules.d/70-*
# reboot

after wakeup, try ifconfig.
now you get your network back.

Salud!

SUDO on FreeBSD

as root install

sudo located at /usr/ports/security/sudo
make configure
make && make install

edit conf at

ee /usr/local/etc/sudoers

example and edit :

# Runas alias specification

# User privilege specification
root ALL=(ALL) ALL
kenan ALL=(www) ALL

note :

This Sudo command limits the user's power on the basis of the configuration made on the file "/etc/sudoers".
Generally in default case you might see something like this:

root ALL=(ALL) ALL
Above, you can see ALL 3 times. But what does it mean?
The first ALL: Run from any(all) host
The Second ALL: From any Terminal
The third ALL: Can Run any command

example :
usename ALL=(group) ALL


** note : !/usr/bin/su (this will prevent user to sudo su)

General sudoers File Record Format
usernames/group servername = (usernames command can be run as) command

Lock / Unlock user on FreeBSD

Lock user :

pw lock nameuser

unlock user :

pw unlock nameuser

Add HDD on VMWARE (FreeBSD)

I just finish adding HDD onto my Vmware server.

the step :

- choose vm that you wish to add the HDD
- edit setting
- add and choose HDD
- follow the instruction
- after adding go to server (freebsd)
- type sysinstall
- choose fdisk
- BEWARE! please make sure your HDD before you format it!
- after you choose your HDD, choose A and W (write the HDD)
- after finish,exit and choose label
- choose C (create) , edit the label and W (write) the HDD.
- edit the fstab (ee /etc/fstab)

example :
but beware too remember the path your HDD before edit the fstab.

/dev/da1s1d /data ufs rw 2 2

- save and reboot.

Setting in FSTAB add HDD in FreeBSD or Unix

ee /etc/fstab

/dev/da2s1 /studentdata ufs rw 2 2

SUDO in FreeBSD / Unix

as root install

sudo located at /usr/ports/security/sudo
make configure
make && make install

edit conf at

ee /usr/local/etc/sudoers

example and edit :

# Runas alias specification

# User privilege specification
root ALL=(ALL) ALL
kenan ALL=(www) ALL

example :
usename ALL=(group) ALL


** note : !/usr/bin/su (this will prevent user to sudo su)

Set environment : setenv EDITOR ee


General sudoers File Record Format
usernames/group servername = (usernames command can be run as) command

example using sudo :

-list the dir-
sudo -u www ls -lah /usr/local/www/apache22/data/

-create a file-
sudo -u www touch /usr/local/www/apache22/data/test

- edit a file-
sudo -u www ee /usr/local/www/apache22/data/test

Check RAM on FreeBSD

Install :

# cd /usr/ports/sysutils/freecolor
# make install clean

$ freecolor -m -o

Set time zone on Ubuntu

Here the CLI :
as root or sudo

dpkg-reconfigure tzdata