Very essential Debian commands

Very essential Debian commands

Update the debian package list:
                root@mahidul:~root@mahidul:~# apt-get update

Upgrade your debian packages:
    root@mahidul:~# apt-get upgrade

Upgrade debian to newer version,
    root@mahidul:~# apt-get dist-upgrade
caution: this may also corrupt your system if you don't have a deeper understanding in Linux don't use it.

Setting the date and time:
        root@mahidul:~# date                 ### check the date
        root@mahidul:~# date --set 12:33:00 ### setting time
        root@mahidul:~# date --set 05-05-2011 ### setting date
        root@mahidul:~# hwclock --systohc       ### sysncronizing
        Or
        root@mahidul:~# date
        root@mahidul:~# date 041516022011
        root@mahidul:~# hwclock --systohc

For Selecting time zone
        root@mahidul:~# dpkg-reconfigure tzdata

For showing Debian version:
        root@mahidul:~# more /etc/issue

DNS show up:
        root@mahidul:~# vim /etc/resolv.conf

Change the host and domain name:
root@mahidul:~# vim /etc/hosts
root@mahidul:~# vim /etc/hostname
root@mahidul:~# cp /etc/hosts /var/spool/postfix/etc/
root@mahidul:~# vim /etc/postfix/transport                                    
        root@mahidul:~# vim /etc/postfix/main.cf

Creating a user account:
        root@mahidul:~# adduser username
                root@mahidul:~# passwd  yourpassword

                If you want to give a dot (.) like user.name then,
root@mahidul:~# adduser --force-badname user.name    (For forcefully write)

Or, you can first add a user then add dot (.) the below files.
                root@mahidul:~# vim /etc/passwd
                user.name        (add a dot(.) between bolcorpbd)
                root@mahidul:~# vim /etc/shadow
                user.name        (add a dot(.) between bolcorpbd)
                root@mahidul:~# vim /etc/groups
                user.name        (add a dot(.) between bolcorpbd)
               

Changing password:
                root@mahidul:~# passwd username
                root@mahidul:~# new password:         (your new password)
                root@mahidul:~# re-type password:         (your new password)

Delete user with directory:
                root@mahidul:~# userdel bolcorp
                root@mahidul:~# rm -rf bolcorp

Delete only user:
                root@mahidul:~# deluser bolcorp Or userdel bolcorp Or rm-rf bolcorp.bd

For creating IP forwarding:
                root@mahidul:~# Vim /etc/sysctl.conf
                Net.ipv4.ip_forward = 1               (UNCOMMENT THE FOLLOWING LINE)

For IP forwarding checking:
                root@mahidul:~# Sysctl -p

Cache delete from squid:
               root@mahidul:~# cd /var/spool/squid
               root@mahidul:~# ls
               root@mahidul:~# rm –rf*

 If configuration is ok but still can not browse then
               root@mahidul:~# cd /var/spool/squid/
               root@mahidul:~# rm -rf swap.state
               root@mahidul:~# rm -rf swap.state.last-clean
               root@mahidul:~# /etc/init.d/squid restart

Checking squid status:
                root@mahidul:~# pgrep squid
                2271    }
                2274    } than squid process is ok
                then check cache.log for checking errors,
                root@mahidul:~# tail -f /var/log/squid/cache.log

This is how you will get the log report with date/time format.
root@mahidul:~# tail -f /var/log/squid/access.log | perl -pe 's/[\d\.]+/localtime($&)/e'
root@mahidul:~# grep 192.168.0.14 /var/log/squid/access.log | perl -pe 's/[\d\.]+/localtime($&)/e'

To close a running process: (List the details of a single process)
                root@mahidul:~# ps aux | grep dansguardian
                root@mahidul:~# pkill-9 dansguardian

For showing mail send /Receive:
                root@mahidul:~# tail –f/var/log/mail.log
                root@mahidul:~# Mlog

To Show client bandwidth for particular user PC:
                root@mahidul:~# ifconfig (to see what type LAN are using such as wth0,eth1)
                root@mahidul:~# if top –I eth1

Mail Sending via telnet:
                root@mahidul:~# telnet localhot 25
                Telnetlocalhost trying 127.0.0.1…
                Connected to localhost.localdomain(127.0.0.1)
                Escape character is`^`]:
                220 mail.ocl-bd.com ESMTP Postfix(2.2.2)
                Helo sam
                250 mail.ocl-bd.com
                Mail from:sam@ocl-bd.com
                250 OK
                Rcpt to:anamul@bol-online.com
                250 Ok
                Data
                354 End data with <CR><LF><CR><LF>
                Test mail
                .
                250 Ok: queued as 57DFF2884C9
                Quit

Mail Box size check:
                root@mahidul:~# cd /var/spool/mail
                root@mahidul:~# ls –alh
                root@mahidul:~# cd /var/mail

Mail box details:
                root@mahidul:~# alpine –f /var/spool/mail/username
                root@mahidul:~# pine –f /var/spool/mail/username
                root@mahidul:~# GetMail username

For showing Particular mail account:  
                root@mahidul:~# grep corp@vashi.com /var/log/mail.log

For check previous mail:
                root@mahidul:~# ped
                root@mahidul:~# ls
                root@mahidul:~# grep “from <”masud@online.com”>” mail.log

Aliasing in Group:
                root@mahidul:~# vim /etc/postfix/aliases
                   #See man 5 aliases for format
                   postmaster:    root

                   #groupname: username1,username2
                   toall: mahidul,test,info

                root@mahidul:~# postalias aliases
                root@mahidul:~# /etc/init.d/postfix restart

Auto Replay (vacation mail) of the account:
                root@mahidul:~# cd /home
                root@mahidul:~# ls
                root@mahidul:~# cd username
                root@mahidul:~# vim message                
                root@mahidul:~# message paste                (place user massage and save the file using ESC+SHIFT+:)

                root@mahidul:~# ls -alh
                root@mahidul:~# mv forward .forward
                root@mahidul:~# mv procmailrc .procmailrc  

If Auto Replay is not configured :
                root@mahidul:~# apt-get install procmail (press enter)
                root@mahidul:~# cd /home/(username) press enter
                root@mahidul:~# ls -al press enter
                root@mahidul:~# vim .procmailrc      

###Now write these script,
#SHELL=/bin/sh
#MAILDIR=$HOME/Mail
#DEFAULT=/var/spool/mail/rafii.zaman
#LOGFILE=$MAILDIR/from
#LOGFILE=/var/log/procmail.log
#LOCKFILE=$HOME/.lockmail

# Anything that has not been delivered by now will go to $DEFAULT
# using LOCKFILE=$DEFAULT$LOCKEXT
#:0 h c
#              * !^FROM_DAEMON
#              * !^X-Loop: rafii.zaman@dzvilo.com
#              | (formail -r -I"Precedence: auto-reply"
#                 -A"X-Loop: rafii.zaman@dzvilo.com" ;
#                 cat $HOME/message; \
#                  ) | $SENDMAIL -oi .t

SHELL=/bin/sh
:0 h c
              * !^FROM_DAEMON
              * !^X-Loop: rafii.zaman@dzvilo.com
              | (formail -r -I"Precedence:junk"  \
                  -A"X-Loop: rafii.zaman@dzvilo.com" ; \
                cat $HOME/message; \
                  ) | $SENDMAIL -oi -t

:0

  ###Then save the file.

  root@mahidul:~# vim .forward (press enter)
                |/usr/bin/procmail        (write the following path)
     

root@mahidul:~# vim message (press enter)
                write down the message which will be Auto replied then save the file.

Removing Auto Replay to an email account:
                root@mahidul:~# cd /home/
                root@mahidul:~# ls -alh
                root@mahidul:~# cd username
                root@mahidul:~# mv .forward forward
                root@mahidul:~# mv .procmailrc procmailrc  

Spam Whitelist user ID: (To show free spam mail)
                root@mahidul:~# vim /etc/MailScanner/rules/spam.whitelist.rules
                root@mahidul:~# /etc/init.d/openprotect restart

Spam whitelist:
                root@mahidul:~# vim /opt/MailScanner-4.82.6-1/etc/rules/spam.whitelist.rules

Spam Site list:
                root@mahidul:~# vim /opt/MailScanner/etc/spam.lists.conf

###Add you spam white list here.
# This is where you can build a Spam WhiteList
# Addresses matching in here, with the value
# "yes" will never be marked as spam.
#From:          152.78.                         yes
#From:          130.246.                        yes
FromOrTo:       yahoo.cn                        yes
FromOrTo:       hpchuazhong.com                 yes
FromOrTo:       sgdgroup.com                    yes
FromOrTo:       tientuan.com.vn                 yes
FromOrTo:       buznan@ifotam.com.pl            Yes
FromOrTo:       default                         no

If SMTP not working / Mail not sending:
                root@mahidul:~# Ps –ef | grep dovecot                 (To show dovecot running / not)
                root@mahidul:~# /etc/init.d/dovecot stop
                root@mahidul:~# /etc/init.d/dovecot start
                root@mahidul:~# telnet clint IP 25                            (first check client side)

Check local connection ok?
                root@mahidul:~# mii-tool
                root@mahidul:~# arp –n
                root@mahidul:~# tail –f /var/log/squid/access.log

Uninstall a package:
                root@mahidul:~# apt-get --purge remove packagename

Client side :
                root@mahidul:~# telnet clientip 25

Show Mail queue:
                root@mahidul:~# mailq

Mail queue flash :
                root@mahidul:~# postfix flash
or
root@mahidul:~# postfix -f

you will list all of the mails which are queued or simply timed out for some reason. If you want to remove a mail from the "mailq" type:
root@mahidul:~# postsuper -d mailID

To remove all mail from the queue:
root@mahidul:~# postsuper -d ALL

Sometime mailscaner holds the mail in que but could not flush then you have to reque the mails like this way:
root@mahidul:~# postsuper -r ALL

To remove all mails in the deferred queue:
root@mahidul:~# postsuper -d ALL deferred

Copy from another server:
                root@mahidul:~# scp MailScanner-install-4.82.6-1.tar.gz 202.161.190.238:/home/mahfuj/

Copy Files from one server(A) to other(B) (While logged into A):
                root@mahidul:~# scp –p 78 FILENAME USERNAME@ADDRESS_OF_REMOTE_SERVER:FILENAME
                For example:
                root@mahidul:~# scp /home/jlwallen/sample.pdf jlwallen@192.168.1.2:/home/jlwallen/sample.pdf

Copy Directory: from A to B(While logged into A):
                root@mahidul:~# scp –r –p78 /home/jlwallen/TEMP jlwallen@192.168.1.2:/home/jlwallen/TEMP

Show all processes:
                root@mahidul:~# ps aux        //similar to ps ux but it would show the process of every user as well as the system.
                which will print out something like:
                113       2596  0.0  0.5  17852 11460 ?        Ss   06:49   0:00 /usr/sbin/dansguardian
                Now we can see the PID of Dansguardian is 2596. We can kill this with the kill 2956 command.

Web browsing package:
                root@mahidul:~# apt-get install lynx
                root@mahidul:~# lynx www.yahoo.com     // use lynx command to browse

Find out a installed package:
                root@mahidul:~# whereis filename
                root@mahidul:~# find filename
                root@mahidul:~# finger filename

Show folder Size:
                root@mahidul:~# du -h

Show pertition Details:
                root@mahidul:~# df -h

Format command in linux:
                root@mahidul:~# sudo mkfs -t ext3 /dev/hda1

Search a file:
               root@mahidul:~# find /-name testfile

Find a new connected device:
               root@mahidul:~# fdisk -l