FreeBSDwiki - User contributions [en]

Uptime

2007-10-26T14:58:21Z

212.30.13.133: Small addition about determining real Linux uptime for the GPL fanboys.

The '''uptime''' command shows the length of time since the system booted up. The output is displayed on the [[standard output]].

<pre>
break# uptime
2:49PM up 229 days, 30 mins, 2 users, load averages: 0.00, 0.00, 0.00
</pre>

The above shows that, at 2:49pm (when the command was run), the system in question had been running for 239 days and 30 minutes. It also had two users logged on. The three load averages values show the system utilisation as at 1, 5 and 15 minutes ago respectively.

Note: FreeBSD does not have an "uptime reset" issue, often referred to as the 497 day roll-over bug, that most Linux and a few UNIX and Unix-like systems do. To determine genuine uptime on systems that are affected by the roll-over bug the following command may be of use '''last -xf /var/run/utmp runlevel'''.

There is a project on the internet called [http://news.netcraft.com/ Netcraft] that monitors uptime of websites. It uses the TCP/IP counter to measure uptime and as such the values are [http://uptime.netcraft.com/up/accuracy.html not always accurate]. That said, the FreeBSD (and other BSDs) are frequently topping the chart with regards to [http://uptime.netcraft.com/up/today/top.avg.html total uptime].

See also [[w]] command.

[[Category:System Commands]]

Talk:Postfix

2007-10-03T13:36:09Z

212.30.13.133: Up for the challenge

so how 'bout giving us a "setting up Postfix" cookbook, Doc? --[[User:Jimbo|Jimbo]] 22:42, 2 October 2007 (EDT)

== Up for the challenge ==

No problem Jimbo - I have built myself an Intel quad core system for the purpose of hosting my FreeBSD systems in VM so I'll quite happily create a guide for Postfix while building my systems. From what I've seen though, I thought you guys were "qmail with everything" people ;-)

Unicode

2007-09-27T14:50:05Z

212.30.13.133: /* Unicode */

== Unicode ==
The simplest form of character set used on computers uses an 8-bit (one byte) numerical value to represent a letter from the English and Latin alphabets and certain accented characters (normally seen in French writing). This system is called [http://en.wikipedia.org/wiki/ASCII ASCII], the American Standard Code for Information Interchange. Almost all modern day operating systems use it as well as many older computer systems.

Unicode, in particular the UTF-8 standard, takes this concept of a numerical value representing a character and extends it to host the alphabets of (virtually) all the known languages in the world. This is around 100,000 characters and as such UTF-8 can use 1-, 2-, 3- and even 4-byte values to represent them:

* the 1-byte character set is used to cover the simple English alphabet;
* the 2-byte character set is used to cover the more common alphabets, including Arabic, Armenian, Cyrillic, Greek, Hebrew, Latin, and Syriac;
* the 3-byte character set is used to cover additional language alphabets;
* the 4-byte character set is used to cover additional, but rarer, language alphabets, as such it is not used often.

In addition to the character sets used the standard also defines "handedness", as in which way the text flows. Typically Western languages are written left-to-right (as per the text on this page) while other, typically middle-Eastern languages, write from right-to-left.

While ASCII uses one character-per-byte and so a 100 letter document would be (theoretically) 100 bytes on disk a Unicode document could be 2, 3 or 4 times that size, depending on the encoding used. The Unicode standard is backwards compatible with ASCII when used in 1-byte character set.

There is another character set typically found on older mainframes, most notably from IBM, called EBCDIC, the Extended Binary-Coded Decimal Interchange Code. There is a variation called [http://en.wikipedia.org/wiki/UTF-EBCDIC UTF-EBCDIC] for these systems where Unicode can exist within legacy applications.

== Using UTF-8 in FreeBSD ==
First we need to set the LC_ALL and LANG variables, find out which locales can support UTF-8.
cd /usr/share/locale/; ls *UTF-8 -d

Add the following environment variables to the appropriate file, ~/.profile or ~/.login or ~/.bashrc.
export LANG=sv_SE.UTF-8
export LC_ALL=sv_SE.UTF-8

Now login and logout to have the effects apply.

== Applications ==
=== xterm ===
To make xterm play nice i added
echo "xterm*locale: UTF-8" >> ~/.Xdefaults

=== irssi + screen ===
If you're like me and don't want to restart your irssi you use the following line, otherwise screen should use the locales.
Ctrl-a : (colon) then write 'encoding UTF-8 UTF-8'

This config will enable you to send ISO8859-1 by default in irssi.
/set term_charset UTF-8
/set recode_out_default_charset ISO8859-1
/set recode yes
/set recode_autodetect_utf8 no
/set recode_fallback ISO8859-1
/set recode_transliterate no
/recode add #utf8channel UTF-8

== External Links ==
* [http://opal.com/freebsd/unicode.html Unicode support on FreeBSD]

Unicode

2007-09-27T14:41:52Z

212.30.13.133: /* Unicode */

== Unicode ==
The simplest form of character set used on computers uses an 8-bit (one byte) numerical value to represent a letter from the English and Latin alphabets and certain accented characters (normally seen in French writing). This system is called [http://en.wikipedia.org/wiki/ASCII ASCII] and almost all modern day operating systems use it as well as many older computer systems.

Unicode, it particular the UTF-8 standard, takes this concept of a numerical value representing a character and extends it to host the alphabets of (virtually) all the known languages in the world. This is around 100,000 characters and as such UTF-8 can use 1-, 2-, 3- and even 4-byte values to represent them:

* the 1-byte character set is used to cover the simple English alphabet;
* the 2-byte character set is used to cover the more common alphabets, including Arabic, Armenian, Cyrillic, Greek, Hebrew, Latin, and Syriac;
* the 3-byte character set is used to cover other language alphabets;
* the 4-byte character set is used to cover rarer language alphabets, as such it is not used often.

In addition to the characters used the standard also defines "handedness", as in which way the text flows. Typically Western languages are written left-to-right (as per the text on this page) while other, typically middle-Eastern languages, write from right-to-left.

While ASCII uses one character-per-byte and so a 100 letter document would be (theoretically) 100 bytes on disk a Unicode document could be 2, 3 or 4 times that size, depending on the encoding used. The Unicode standard is backwards compatible with ASCII when used in 1-byte character set.

== Using UTF-8 in FreeBSD ==
First we need to set the LC_ALL and LANG variables, find out which locales can support UTF-8.
cd /usr/share/locale/; ls *UTF-8 -d

Add the following environment variables to the appropriate file, ~/.profile or ~/.login or ~/.bashrc.
export LANG=sv_SE.UTF-8
export LC_ALL=sv_SE.UTF-8

Now login and logout to have the effects apply.

== Applications ==
=== xterm ===
To make xterm play nice i added
echo "xterm*locale: UTF-8" >> ~/.Xdefaults

=== irssi + screen ===
If you're like me and don't want to restart your irssi you use the following line, otherwise screen should use the locales.
Ctrl-a : (colon) then write 'encoding UTF-8 UTF-8'

This config will enable you to send ISO8859-1 by default in irssi.
/set term_charset UTF-8
/set recode_out_default_charset ISO8859-1
/set recode yes
/set recode_autodetect_utf8 no
/set recode_fallback ISO8859-1
/set recode_transliterate no
/recode add #utf8channel UTF-8

== External Links ==
* [http://opal.com/freebsd/unicode.html Unicode support on FreeBSD]

User:DrModiford

2007-09-04T13:09:15Z

212.30.13.133: /* Knowledge */

Okay, so I'm not really a doctor...

= About =

I started out on a Commodore 16 back when I was four and progressed through various computing platforms, most notably Windows and then Linux, before discovering FreeBSD several years ago. Since then I have had a long-term love affair with this operating system!

I live in the offshore finance centre of Guernsey, part of the Channel Islands which sit between the mainlands of UK and France, and work within the IT department of a fiduciary (trust / finance industry) company.

= Knowledge =

I have been privileged through my career to have used many different computing platforms from the humble BBC Micro to large-scale IBM AS/400s. After discovering FreeBSD I became proficient at deploying, implementing and maintaining it in both personal and corporate environments.

At home it has been used to host my web and email server over an ADSL connection and as a Samba file server to store music and movies.

In the office it is used to monitor network traffic with MRTG, host an internal Wikipedia for application development documentation, allow marketing to mass-mail intermediaries using qmail and host SecureFTP file distribution on-line.

= Contact =

I look forward to chatting with any like-minded FreeBSD users out there. I can be contacted on:

* ICQ: 59-397-985 or;
* MSN: glynb at hotmail dot co dot uk.

Of course, I use those accounts through KDE Kopete on a laptop running PC-BSD!

Postfix

2007-09-04T12:50:53Z

212.30.13.133: /* Support Servers */

Postfix is an MTA (mail transfer agent) that is intended to be a replacement of the default Sendmail MTA used on many Unix and Unix-like platforms, including FreeBSD. Postfix is considered to be a faster, easier to manage and more secure then Sendmail. It also has the advantage of using the same configuration file options that Sendmail uses to simplify migration and reduce the need to learn a new system.

Postfix itself is simply an SMTP server capable of receiving and delivering email to other SMTP servers. Client applications such as Mozilla Thunderbird or Microsoft Outlook cannot receive mail directly from Postfix. To enable mail retrieval the Postfix server is typically run alongside another server capable of handling POP3 and/or IMAP4 requests (see below for support servers).

== Origins ==

Postfix began as a program called VMailer and later became IBM Secure Mailer before being released as Postfix in 1999 under the [http://en.wikipedia.org/wiki/IBM_Public_License IBM Public License 1.0]. This license makes Postfix free software but is not compatible with the GPL. It continues to be actively developed and has its own [http://www.postfix.org/ website].

== Features ==

Postfix has the following features (references taken from the [http://en.wikipedia.org/wiki/Postfix_%28software%29 Wikipedia] entry for Postfix).

=== Storage ===

Received email can be stored in the following file-based mailboxes

* [http://en.wikipedia.org/wiki/Mbox mbox] - a single, flat-file containing all emails addressed to a recipient;
* [http://en.wikipedia.org/wiki/Maildir Maildir] - a single directory, usually located under the user's home directory, containing a file per email received;
* virtual domains;

=== Mappings ===

Mail mapping can be stored in the following database-based formats:

* [http://en.wikipedia.org/wiki/Berkeley_DB Berkley DB] - a simple but effective database system but does not network;
* [http://en.wikipedia.org/wiki/Constant_Data_Base CDB] - a quick and effective database designed around the file system;
* DBM;
* [http://en.wikipedia.org/wiki/Lightweight_Directory_Access_Protocol LDAP] - a hierarchical system often used for authentication (Microsoft adapted LDAP to create their Active Directory system);
* [http://en.wikipedia.org/wiki/MySQL MySQL] - a real SQL database system similar to Microsoft and Oracle SQL servers;
* [http://en.wikipedia.org/wiki/PostgreSQL PostgreSQL] - a real SQL database system similar to Microsoft and Oracle SQL servers.

=== Addressing ===

=== Security ===

Security has been enhanced with the following features:

* Transport Layer Security (TLS);
* Delegation of SMTP policies to an external process (this allows Greylisting) and advanced content filtering;
* VERP;
* SMTP-AUTH via SASL;
* Others;
* Milter support.

One of the strengths of Postfix is its resilience against buffer overflows. Another one is its handling of large amounts of e-mail. Postfix is built as a cooperating network of different daemons. Each daemon fulfills a single task using minimum privileges. In this way, if a daemon is compromised, the impact remains limited to that daemon and cannot spread throughout the entire system. There is only one process with root privileges (master), and a few (local, virtual, pipe) that actually write to disk or invoke external programs. Most daemons can be easily chrooted.

=== Portability ===

Postfix can also be compiled on AIX, BSD, HP-UX, IRIX, Linux, Mac OS X, Solaris, Tru64 UNIX and, generally speaking, on every Unix-like OS that ships with a C compiler, standard POSIX development libraries and all the libraries required for handling BSD sockets.

== Support Servers ==

Postfix is limited to the sending and reception of email using the SMTP protocol. This does not permit email clients to retrieve email from it in a simple user-friendly manner. This is where a support server can be run alongside Postfix to provide email clients with a method to retrieve stored email messages. The common protocols used by email clients are POP3 and IMAP4. POP3 is typically used by ISPs and internet facing mail services and IMAP4 is typically used on private corporate networks.

In simple terms POP3 is a mail retrieval protocol that allows an email client download any and all emails to the local host. Usually emails are removed from the server so only the client copy exists. This differs to IMAP4 where an email client will view the emails available but they will be retained on the server until the client deletes them.

There are numerous support servers available to handle POP3 and/or IMAP4 both open source and commercial. The following list contains open source implementations available from the FreeBSD ports system:

* [http://www.bincimap.org/ BINC IMAP] - this aims to be stable, fast, flexible, and RFC compliant, available under the GPL;
* [http://www.courier-mta.org/ Courier MTA] - Courier is a modular multiprotocol mail server that's designed to strike a balance between reasonable performance, flexibility and multiple features;
* [http://cyrusimap.web.cmu.edu/ Cyrus IMAP] - The Cyrus IMAP server is a scaleable enterprise mail system designed for use from small to large enterprise environments using standards-based technologies;
* [http://www.dovecot.org/ Dovecot] - relatively new but maturing, fast and secure implementation of the POP3 and IMAP4 protocols;
* [http://www.washington.edu/imap/ UW IMAP] - This is the IMAP4rev1 server from the University of Washington. Included are (almost) backwards-compatible POP2 and POP3 servers.

[[Category:FreeBSD for Servers]]