Install Postfix MTA (Mail Transfer Agent)
Use the following command to install postfix in debian
#aptitude install postfix postfix-tls libsasl2 sasl2-bin libsasl2-modules popa3d
During installation, postfix will ask for few questions like name of server and answer those questions by entering your domain name and select Internet site for postfix.
Postfix configuration file is located at:/etc/postfix/main.cf. You can edit this file using popular text editor vi /etc/postfix/main.cf
Restart Postfix Server using the following command
#/etc/init.d/postfix restart
Install Dovecot
Dovecot is POP3/IMAP server which needs MTA like Postfix to work properly.
#aptitude install dovecot-imapd dovecot-pop3d dovecot-common
Dovecot configuration file is located at: /etc/dovecot/dovecot.conf
Before we proceed we need to make some changes with dovecot configuration file. Double check the following entries in the file if the values are entered properly.
Edit the dovecot configuration file using the following command
#vi /etc/dovecot/dovecot.conf
# specify protocols = imap imaps pop3 pop3s
protocols = pop3 imap
# uncomment this and change to no.
disable_plaintext_auth = no
pop3_uidl_format = %08Xu%08Xv
Now, create a user to test our pop3 mail with outlook:
#adduser user_name
Note: Always create a separate user to test your mail or ftp.
Restart Dovecot using the following command
#/etc/init.d/dovecot restart
Now, you can use your outlook express to test whether your new mail server is working or not. Just enter username: with password in outlook.
Remember you will NOT be able to send email outside your network, you will be only be able to send within your domain or local network. If you attempt to send email you get “relay access denied” error from outlook express. However, you should have no problems in receiving your email from outlook. Inorder to send email external email you will need to configure SASL authentication as described below.
Configure SASL Authentication with TLS
SASL Configuration + TLS (Simple authentication security layer with transport layer security) used mainly to authenticate users before sending email to external server, thus restricting relay access. If your relay server is kept open, then spammers could use your mail server to send spam. It is very essential to protect your mail server from misuse.
Let us set up SMTP authentication for our users with postfix and dovecot.
Edit the postfix configuration file /etc/postfix/main.cf and enter the few lines to enable authentication of our users
smtpd_sasl_auth_enable = yes
smtpd_sasl_local_domain = yourdomain.com
smtpd_recipient_restrictions = permit_mynetworks,permit_sasl_authenticated,reject_unauth_destination
smtpd_sasl_security_options = noanonymous
postfix does a chroot so it can’t communicate with saslauthd.
#rm -r /var/run/saslauthd/
#mkdir -p /var/spool/postfix/var/run/saslauthd
#ln -s /var/spool/postfix/var/run/saslauthd /var/run
#chgrp sasl /var/spool/postfix/var/run/saslauthd
#adduser postfix sasl
On the Dovecot side you also need to specify the dovecot authentication daemon socket. In this case we specify an absolute pathname. Refer to this postfix manual here
Edit /etc/dovecot/dovecot.conf file
#vi /etc/dovecot/dovecot.conf
Look for the line that starts with auth default, before that insert the lines below.
auth default {
mechanisms = plain login
passdb pam {
}
userdb passwd {
}
socket listen {
client {
path = /var/spool/postfix/private/auth
mode = 0660
user = postfix
group = postfix
}
}
}
Now, rename previous auth default to auth default2. If you dont rename this then dovecot server will give you error like multiple instances of auth default.
Now restart all the following components of mail server
#/etc/init.d/saslauthd restart
#/etc/init.d/postfix restart
#/etc/init.d/dovecot restart
Test whether your mail server works or not with your outlook express. Configure a user with a user name (without @domain) and make sure that you select my server requires authentication. Under settings select same as incoming mail server
Note:
1. If you dont enable My server requires authentication in outlook you cannot send emails to external recipients and you get relay access denied error.
2. Do not use root login to login to your mail server.
3. Dont forget to create a new user before you authenticate using outlook.
Forwarding Mails
Ever wondered how to forward your mails especially if you are a webmaster managing number of sites. You might need to forward any email sent to your primary email address. Its that easy. Just create a .forward file on your home directory. Insert list of emails addresses separated by commas, where you want to get forwarded.
Login as user and type
echo ‘destination_email_address’ > .forward
or you can use vi to create .forward file. Just Delete .forward file if you dont want any forwarding.
Installing Squirrel Web Mail
Before installing Squirrel Web Mail you need to make sure you have installed apache2 with php support
#aptitude install apache2
#aptitude install libapache2-mod-php5 php5-cli php5-common php5-cgi
#aptitude install squirrelmail
Squirrelmail configuration file is located in: /etc/squirrelmail/ folder. By default all settings are preloaded.
# Run squirrelmail configuration utility as ROOT
/usr/sbin/squirrelmail-configure
Now we want to setup to run under apache. Edit apache configuration file /etc/apache2/apache2.conf and insert the following line
Include /etc/squirrelmail/apache.conf
Restart the webserver using the following command
#/etc/init.d/apache2 restart
Access your webmail using the following link
http://yourdomain or server ip/squirrelmail
Create a separate local user and login as a new user.
Mail Server Logs
Always refer to logs located in /var/log/mail.log so that you can identify what the problem is before you can troubleshoot.
Thursday, February 4, 2010
A detailed look at the filesystem in Debian
A typical Linux system has, among others, the following directories:
/
This is the root directory. This is where the whole tree starts.
/bin
This directory contains executable programs which are needed in single user mode and to bring the system up or repair it.
/boot
Contains static files for the boot loader. This directory only holds the files which are needed during the boot process.
/dev
Special or device files, which refer to physical devices.
/etc
Contains configuration files which are local to the machine. Some larger software packages, like X11, can have their own subdirectories below /etc. Site-wide configuration files may be placed here or in /usr/etc. Nevertheless, programs should always look for these files in /etc and you may have links for these files to /usr/etc.
/etc/skel
When a new user account is created, files from this directory are usually copied into the user's home directory.
/etc/X11
Configuration files for the X11 window system.
/home
On machines with home directories for users, these are usually beneath this directory, directly or not. The structure of this directory depends on local administration decisions.
/lib
This directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem.
/mnt
is a mount point for temporarily mounted filesystems
/proc
This is a mount point for the proc filesystem, which provides information about running processes and the kernel.
/sbin
Like /bin, this directory holds commands needed to boot the system, but which are usually not executed by normal users.
/tmp
This directory contains temporary files which may be deleted with no notice, such as by a regular job or at system boot up.
/usr
This directory is usually mounted from a separate partition. It should hold only sharable, read-only data, so that it can be mounted by various machines running Linux.
/usr/X11R6
The X-Window system.
/usr/bin
This is the primary directory for executable pro grams. Most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be placed in this directory.
/usr/bin/X11
is the traditional place to look for X11 executable's; on Linux, it usually is a symbolic link to /usr/X11R6/bin.
/usr/dict
This directory holds files containing word lists for spell checkers.
/usr/doc
You may find documentation about the installed software packages in this directory.
/usr/etc
Site-wide configuration files to be shared between several machines may be stored in this directory. However, commands should always reference those files using the /etc directory. Links from files in /etc should point to the appropriate files in /usr/etc.
/usr/include
Include files for the C compiler.
/usr/include/X11
Include files for the C compiler and the X-Windows system. This is usually a symbolic link to /usr/X11R6/include/X11.
/usr/include/asm
Include files which declare some assembler functions. This used to be a symbolic link to /usr/src/linux/include/asm.
/usr/include/linux
This contains information which may change from system release to system release and used to be a symbolic link to /usr/src/linux/include/linux to get at operating system specific information.
(Note that one should have include files there that work correctly with the current libc and in user space. However, Linux kernel source is not designed to be used with user programs and does not know anything about the libc you are using. It is very likely that things will break if you let /usr/include/asm and /usr/include/linux point at a random kernel tree. Debian systems don't do this and use headers from a known good kernel version, provided in the libc*-dev package.)
Include files to use with the GNU C++ compiler.
/usr/lib
Object libraries, including dynamic libraries, plus some executable's which usually are not invoked directly. More complicated programs may have whole subdirectories there.
/usr/lib/X11
The usual place for data files associated with X programs, and configuration files for the X system itself. On Linux, it usually is a symbolic link to /usr/X11R6/lib/X11
/usr/lib/gcc-lib
contains executable's and include files for the GNU C compiler.
/usr/lib/groff
Files for the GNU groff document formatting system.
/usr/local
This is where programs which are local to the site typically go.
/usr/local/bin
Binaries for programs local to the site go there.
/usr/local/doc
Local documentation
/usr/local/etc
Configuration files associated with locally installed programs go there.
/usr/local/lib
Files associated with locally installed programs go there.
/usr/local/info
Info pages associated with locally installed pro grams go there.
/usr/local/man
Manpages associated with locally installed programs go there.
/usr/local/sbin
Locally installed programs for system administration.
/usr/local/src
Source code for locally installed software.
/usr/man
Manpages traditionally go in there, into their sub directories.
/usr/sbin
This directory contains program binaries for system administration which are not essential for the boot process, for mounting /usr, or for system repair.
/usr/share
This directory contains subdirectories with specific application data, that can be shared among different architectures of the same OS. Often one finds stuff here that used to live in /usr/doc or /usr/lib or /usr/man.
/usr/share/man
Manpages go in there, into their subdirectories.
/usr/src
Source files for different parts of the system, included with some packages for reference purposes. Don't work here with your own projects, as files below /usr should be read-only except when installing software
/usr/src/linux
This has always been the traditional place where kernel sources were unpacked. This was important on systems that /usr/include/linux was a symlink here. You should probably use another directory for building the kernel now.
/usr/tmp
Obsolete. This should be a link to /var/tmp. This link is present only for compatibility reasons and shouldn't be used.
/var
This directory contains files which may change in size, such as spool and log files.
/var/adm
This directory is superseded by /var/log and should be a symbolic link to /var/log.
/var/backups
This directory is used to save backup copies of important system files.
/var/lock
Lock files are placed in this directory. The naming convention for device lock files is LCK.. where is the device's name in the filesystem. The format used is that of HDU UUCP lock files, i.e. lock files contain a PID as a 10-byte ASCII decimal number, followed by a newline character.
/var/log
Miscellaneous log files.
/var/preserve
This is where vi saves edit sessions so they can be restored later.
/var/run
Run-time variable files, like files holding process identifiers (PIDs) and logged user information (utmp). Files in this directory are usually cleared when the system boots.
/var/spool
Spooled (or queued) files for various programs.
/var/spool/at
Spooled jobs for at(1).
/var/spool/cron
Spooled jobs for cron
/var/spool/lpd
Spooled files for printing.
/var/spool/mail
Users' mailboxes.
/var/tmp
Like /tmp, this directory holds temporary files stored for an unspecified duration.
/
This is the root directory. This is where the whole tree starts.
/bin
This directory contains executable programs which are needed in single user mode and to bring the system up or repair it.
/boot
Contains static files for the boot loader. This directory only holds the files which are needed during the boot process.
/dev
Special or device files, which refer to physical devices.
/etc
Contains configuration files which are local to the machine. Some larger software packages, like X11, can have their own subdirectories below /etc. Site-wide configuration files may be placed here or in /usr/etc. Nevertheless, programs should always look for these files in /etc and you may have links for these files to /usr/etc.
/etc/skel
When a new user account is created, files from this directory are usually copied into the user's home directory.
/etc/X11
Configuration files for the X11 window system.
/home
On machines with home directories for users, these are usually beneath this directory, directly or not. The structure of this directory depends on local administration decisions.
/lib
This directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem.
/mnt
is a mount point for temporarily mounted filesystems
/proc
This is a mount point for the proc filesystem, which provides information about running processes and the kernel.
/sbin
Like /bin, this directory holds commands needed to boot the system, but which are usually not executed by normal users.
/tmp
This directory contains temporary files which may be deleted with no notice, such as by a regular job or at system boot up.
/usr
This directory is usually mounted from a separate partition. It should hold only sharable, read-only data, so that it can be mounted by various machines running Linux.
/usr/X11R6
The X-Window system.
/usr/bin
This is the primary directory for executable pro grams. Most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be placed in this directory.
/usr/bin/X11
is the traditional place to look for X11 executable's; on Linux, it usually is a symbolic link to /usr/X11R6/bin.
/usr/dict
This directory holds files containing word lists for spell checkers.
/usr/doc
You may find documentation about the installed software packages in this directory.
/usr/etc
Site-wide configuration files to be shared between several machines may be stored in this directory. However, commands should always reference those files using the /etc directory. Links from files in /etc should point to the appropriate files in /usr/etc.
/usr/include
Include files for the C compiler.
/usr/include/X11
Include files for the C compiler and the X-Windows system. This is usually a symbolic link to /usr/X11R6/include/X11.
/usr/include/asm
Include files which declare some assembler functions. This used to be a symbolic link to /usr/src/linux/include/asm.
/usr/include/linux
This contains information which may change from system release to system release and used to be a symbolic link to /usr/src/linux/include/linux to get at operating system specific information.
(Note that one should have include files there that work correctly with the current libc and in user space. However, Linux kernel source is not designed to be used with user programs and does not know anything about the libc you are using. It is very likely that things will break if you let /usr/include/asm and /usr/include/linux point at a random kernel tree. Debian systems don't do this and use headers from a known good kernel version, provided in the libc*-dev package.)
Include files to use with the GNU C++ compiler.
/usr/lib
Object libraries, including dynamic libraries, plus some executable's which usually are not invoked directly. More complicated programs may have whole subdirectories there.
/usr/lib/X11
The usual place for data files associated with X programs, and configuration files for the X system itself. On Linux, it usually is a symbolic link to /usr/X11R6/lib/X11
/usr/lib/gcc-lib
contains executable's and include files for the GNU C compiler.
/usr/lib/groff
Files for the GNU groff document formatting system.
/usr/local
This is where programs which are local to the site typically go.
/usr/local/bin
Binaries for programs local to the site go there.
/usr/local/doc
Local documentation
/usr/local/etc
Configuration files associated with locally installed programs go there.
/usr/local/lib
Files associated with locally installed programs go there.
/usr/local/info
Info pages associated with locally installed pro grams go there.
/usr/local/man
Manpages associated with locally installed programs go there.
/usr/local/sbin
Locally installed programs for system administration.
/usr/local/src
Source code for locally installed software.
/usr/man
Manpages traditionally go in there, into their sub directories.
/usr/sbin
This directory contains program binaries for system administration which are not essential for the boot process, for mounting /usr, or for system repair.
/usr/share
This directory contains subdirectories with specific application data, that can be shared among different architectures of the same OS. Often one finds stuff here that used to live in /usr/doc or /usr/lib or /usr/man.
/usr/share/man
Manpages go in there, into their subdirectories.
/usr/src
Source files for different parts of the system, included with some packages for reference purposes. Don't work here with your own projects, as files below /usr should be read-only except when installing software
/usr/src/linux
This has always been the traditional place where kernel sources were unpacked. This was important on systems that /usr/include/linux was a symlink here. You should probably use another directory for building the kernel now.
/usr/tmp
Obsolete. This should be a link to /var/tmp. This link is present only for compatibility reasons and shouldn't be used.
/var
This directory contains files which may change in size, such as spool and log files.
/var/adm
This directory is superseded by /var/log and should be a symbolic link to /var/log.
/var/backups
This directory is used to save backup copies of important system files.
/var/lock
Lock files are placed in this directory. The naming convention for device lock files is LCK..
/var/log
Miscellaneous log files.
/var/preserve
This is where vi saves edit sessions so they can be restored later.
/var/run
Run-time variable files, like files holding process identifiers (PIDs) and logged user information (utmp). Files in this directory are usually cleared when the system boots.
/var/spool
Spooled (or queued) files for various programs.
/var/spool/at
Spooled jobs for at(1).
/var/spool/cron
Spooled jobs for cron
/var/spool/lpd
Spooled files for printing.
/var/spool/mail
Users' mailboxes.
/var/tmp
Like /tmp, this directory holds temporary files stored for an unspecified duration.
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