From b463f1fbb5b05daa65fd3c320031b4aebf24692d Mon Sep 17 00:00:00 2001 From: Zhang Huangbin Date: Wed, 7 Feb 2018 23:55:31 +0800 Subject: [PATCH] New: integration.netdata.freebsd.html. --- .../0-integration.netdata.freebsd.md | 278 +++++++++++++++ .../0-integration.netdata.linux.md | 81 ++++- html/integration.netdata.freebsd.html | 318 ++++++++++++++++++ html/integration.netdata.linux.html | 92 +++-- 4 files changed, 737 insertions(+), 32 deletions(-) create mode 100644 en_US/integrations/0-integration.netdata.freebsd.md create mode 100644 html/integration.netdata.freebsd.html diff --git a/en_US/integrations/0-integration.netdata.freebsd.md b/en_US/integrations/0-integration.netdata.freebsd.md new file mode 100644 index 00000000..3cc79230 --- /dev/null +++ b/en_US/integrations/0-integration.netdata.freebsd.md @@ -0,0 +1,278 @@ +# Integrate netdata monitor (on FreeBSD server) + +[TOC] + +!!! attention + + * This tutorial is tested on FreeBSD 11.x. If you need to run netdata on + CentOS, Debian, Ubuntu, please check this tutorial instead: + [Integrate netdata on Linux](./integration.netdata.linux.html). + * netdata is an optional component since iRedMail-0.9.8. + +## What's netdata + +netdata () is a "Simple. Effective. Awesome!" monitor +which can monitor almost everyting on your Linux/FreeBSD system. You can visit +its website to check online demo. + +We will show you how to install and configure netdata on iRedMail server +(Linux) to monitor mail service related softwares. + +## Install netdata + +``` +cd /usr/ports/net-mgmt/netdata +make install clean +``` + +## Configure netdata + +Main config file of netdata is `/usr/local/etc/netdata/netdata.conf`, it +contains many parameters with detailed comments. Here's the +[config file](https://bitbucket.org/zhb/iredmail/src/default/iRedMail/samples/netdata/netdata.conf) +used by iRedMail: + +* It binds to address `127.0.0.1` and port `19999` by default. Since it doesn't + have ACL control, we will run netdata behind Nginx to get ACL control done in + Nginx. + +``` +[registry] + enabled = no + +[global] + bind to = 127.0.0.1 + run as user = netdata + default port = 19999 + update every = 3 + +[plugin:proc] + # Disable IPVS check since iRedMail doesn't use ipvs by default + /proc/net/ip_vs/stats = no + + # inbound packets dropped + /proc/net/dev = no +``` + +netdata ships a lot modular config files to gather information of softwares +running on the server, they have very good default settings and most config +files don't need your attention at all, including: + +* System resources (CPU, RAM, disk I/O, etc) +* Nginx log file monitoring +* Fail2ban jails +* Memcached +* ... + +But some applications do require extra settings, we will cover them below. + +### Monitor Nginx and php-fpm + +We need to enable `stub_status` in Nginx to get detailed server info, also +update php-fpm config file to enable similar feature. + +* Create Nginx config snippet `/usr/local/etc/nginx/templates/stub_status.tmpl` with + content below: + +``` +location = /stub_status { + stub_status on; + access_log off; + allow 127.0.0.1; + deny all; +} + +location = /status { + include fastcgi_params; + fastcgi_pass php_workers; + fastcgi_param SCRIPT_FILENAME $fastcgi_script_name; + access_log off; + allow 127.0.0.1; + deny all; +} +``` + +* Update default virtual host config file `/usr/local/etc/nginx/sites-enabled/00-default.conf`, + include new snippet config file `stub_status.tmpl` after the + `redirect_to_https.tmpl` line like below: + +``` +server { + ... + include /usr/local/etc/nginx/templates/redirect_to_https.tmpl; + include /usr/local/etc/nginx/templates/stub_status.tmpl; # <- add this line + ... +} +``` + +* Update php-fpm pool config file `/usr/local/etc/php-fpm.d/www.conf`, enable + parameter `pm.status_path` like below: + +``` +pm.status_path = /status +``` + +* Restart both php-fpm and Nginx service. + +### Monitor Dovecot + +We need to enable statistics module in Dovecot. + +* Please open Dovecot config file `/usr/local/etc/dovecot/dovecot.conf`, + append plugin `stats` in global parameter `mail_plugins`, and `imap_stats` + for imap protocol: + +``` +mail_plugins = ... stats + +protocol imap { + mail_plugins = ... imap_stats + ... +} +``` + +* Append settings below in Dovecot config file: + +``` +plugin { + # how often to session statistics (must be set) + stats_refresh = 30 secs + # track per-IMAP command statistics (optional) + stats_track_cmds = yes +} + +service stats { + fifo_listener stats-mail { + user = vmail + mode = 0644 + } + + inet_listener { + address = 127.0.0.1 + port = 24242 + } +} +``` + +* Restart Dovecot service. + +### Monitor MySQL/MariaDB server + +netdata requires a SQL user (we use `netdata` here) with privilege `USAGE` to +gather MySQL server information. + +* Create the SQL user with a strong password (please replace `` in + command below by the real (and strong) password). + +``` +# mysql -u root +sql> GRANT USAGE ON *.* TO netdata@localhost IDENTIFIED BY ''; +sql> FLUSH PRIVILEGES; +``` + +* Create file `/usr/local/etc/netdata/python.d/mysql.conf` with content below. + + !!! attention + + * This file already exists, feel free to remove all content in this file + and copy content below as its new content. + * Please replace `` below by the real password. + +``` +tcp: + name: 'local' + host: '127.0.0.1' + port: '3306' + user: 'netdata' + pass: '' +``` + +### Monitor PostgreSQL server + +netdata requires a SQL user (we use `netdata` here) to gather PostgreSQL server +information. + +* Create the SQL user with a strong password (please replace `` in + command below by the real (and strong) password). + +``` +# su - postgres +$ psql +sql> CREATE USER netdata WITH ENCRYPTED PASSWORD '' NOSUPERUSER NOCREATEDB NOCREATEROLE; +``` + +* Create file `/usr/local/etc/netdata/python.d/mysql.conf` with content below. + + !!! attention + + * This file already exists, feel free to remove all content in this file + and copy content below as its new content. + * Please replace `` below by the real password. + +``` +socket: + name : 'local' + user : 'netdata' + password : '' + database : 'postgres' +``` + +## Configure Nginx to forward requests to netdata + +* Create Nginx config snippet `/usr/local/etc/nginx/templates/netdata.tmpl` with + content below: + +``` +# Running netdata as a subfolder to an existing virtual host +# FYI: https://github.com/firehol/netdata/wiki/Running-behind-nginx + +location = /netdata { + return 301 /netdata/; +} + +location ~ /netdata/(?.*) { + proxy_redirect off; + proxy_set_header Host $host; + + proxy_set_header X-Forwarded-Host $host; + proxy_set_header X-Forwarded-Server $host; + proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; + proxy_http_version 1.1; + proxy_pass_request_headers on; + proxy_set_header Connection "keep-alive"; + proxy_store off; + proxy_pass http://netdata/$ndpath$is_args$args; + + gzip on; + gzip_proxied any; + gzip_types *; + + auth_basic "Authentication Required"; + auth_basic_user_file /usr/local/etc/nginx/netdata.users; +} +``` + +* Update default virtual host (https site) config file + `/usr/local/etc/nginx/sites-enabled/00-default-ssl.conf`, + include new snippet config file `netdata.tmpl` before the + `misc.tmpl` line like below: + +``` +server { + ... + include /usr/local/etc/nginx/templates/netdata.tmpl; # <- add this line + include /usr/local/etc/nginx/templates/misc.tmpl; + ... +} +``` + +* Create new file `/usr/local/etc/nginx/netdata.users` and an account used to access + netdata. NOTE: Please replace `` below by a real, strong password. + +``` +touch /usr/local/etc/nginx/netdata.users +doveadm pw -s SSHA -p '' +``` + +* Now restart nginx service and access url `https://your-server/netdata/` + (please replace `your-server` by the real domain name). diff --git a/en_US/integrations/0-integration.netdata.linux.md b/en_US/integrations/0-integration.netdata.linux.md index 8bcf638f..56e51c21 100644 --- a/en_US/integrations/0-integration.netdata.linux.md +++ b/en_US/integrations/0-integration.netdata.linux.md @@ -4,9 +4,10 @@ !!! attention - This tutorial is tested on CentOS 7, Debian 9, Ubuntu 16.04. - For FreeBSD, please check this tutorial instead: - [Integrate netdata on FreeBSD](./integration.netdata.freebsd.html). + * This tutorial is tested on CentOS 7, Debian 9, Ubuntu 16.04. + For FreeBSD, please check this tutorial instead: + [Integrate netdata on FreeBSD](./integration.netdata.freebsd.html). + * netdata is an optional component since iRedMail-0.9.8. ## What's netdata @@ -148,8 +149,6 @@ server { * On RHEL/CentOS, it's `/etc/php-fpm.d/www.conf` * On Debian, it's `/etc/php5/fpm/pool.d/www.conf` * On Ubuntu, it's `/etc/php/7.0/fpm/pool.d/www.conf` (note: php version number may be different on your server) - * On FreeBSD, it's `/usr/local/etc/php-fpm.d/www.conf` - * On OpenBSD, it's `/etc/php-fpm.conf` ``` pm.status_path = /status @@ -161,18 +160,16 @@ pm.status_path = /status We need to enable statistics module in Dovecot. -* Please open Dovecot config file: - * on Linux and OpenBSD, its `/etc/dovecot/dovecot.conf`. - * on FreeBSD, it's `/usr/local/etc/dovecot/dovecot.conf`. - -* Append plugin `stats` in global parameter `mail_plugins`, and `imap_stats` - for imap protocol: +* Please open Dovecot config file `/etc/dovecot/dovecot.conf`, append plugin + `stats` in global parameter `mail_plugins`, and `imap_stats` for imap protocol: ``` mail_plugins = ... stats protocol imap { mail_plugins = ... imap_stats + ... +} ``` * Append settings below in Dovecot config file: @@ -261,8 +258,6 @@ socket: database : 'postgres' ``` -## Configure Nginx to forward requests to netdata - ## System tuning To get better performance, netdata requires few sysctl settings. Please add @@ -292,3 +287,63 @@ Reload systemd daemon: ``` systemctl daemon-reload ``` + +## Configure Nginx to forward requests to netdata + +* Create Nginx config snippet `/etc/nginx/templates/netdata.tmpl` with + content below: + +``` +# Running netdata as a subfolder to an existing virtual host +# FYI: https://github.com/firehol/netdata/wiki/Running-behind-nginx + +location = /netdata { + return 301 /netdata/; +} + +location ~ /netdata/(?.*) { + proxy_redirect off; + proxy_set_header Host $host; + + proxy_set_header X-Forwarded-Host $host; + proxy_set_header X-Forwarded-Server $host; + proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; + proxy_http_version 1.1; + proxy_pass_request_headers on; + proxy_set_header Connection "keep-alive"; + proxy_store off; + proxy_pass http://netdata/$ndpath$is_args$args; + + gzip on; + gzip_proxied any; + gzip_types *; + + auth_basic "Authentication Required"; + auth_basic_user_file /etc/nginx/netdata.users; +} +``` + +* Update default virtual host (https site) config file + `/etc/nginx/sites-enabled/00-default-ssl.conf`, + include new snippet config file `netdata.tmpl` before the + `misc.tmpl` line like below: + +``` +server { + ... + include /etc/nginx/templates/netdata.tmpl; # <- add this line + include /etc/nginx/templates/misc.tmpl; + ... +} +``` + +* Create new file `/etc/nginx/netdata.users` and an account used to access + netdata. NOTE: Please replace `` below by a real, strong password. + +``` +touch /etc/nginx/netdata.users +doveadm pw -s SSHA -p '' +``` + +* Now restart nginx service and access url `https://your-server/netdata/` + (please replace `your-server` by the real domain name). diff --git a/html/integration.netdata.freebsd.html b/html/integration.netdata.freebsd.html new file mode 100644 index 00000000..267971b2 --- /dev/null +++ b/html/integration.netdata.freebsd.html @@ -0,0 +1,318 @@ + + + + + Integrate netdata monitor (on FreeBSD server) + + + + +

Integrate netdata monitor (on FreeBSD server)

+
+ +
+
+

Attention

+
    +
  • This tutorial is tested on FreeBSD 11.x. If you need to run netdata on + CentOS, Debian, Ubuntu, please check this tutorial instead: + Integrate netdata on Linux.
    • +
  • netdata is an optional component since iRedMail-0.9.8.
    • +
+
+

What's netdata

+

netdata (http://my-netdata.io) is a "Simple. Effective. Awesome!" monitor +which can monitor almost everyting on your Linux/FreeBSD system. You can visit +its website to check online demo.

+

We will show you how to install and configure netdata on iRedMail server +(Linux) to monitor mail service related softwares.

+

Install netdata

+
cd /usr/ports/net-mgmt/netdata
+make install clean
+
+ +

Configure netdata

+

Main config file of netdata is /usr/local/etc/netdata/netdata.conf, it +contains many parameters with detailed comments. Here's the +config file +used by iRedMail:

+
    +
  • It binds to address 127.0.0.1 and port 19999 by default. Since it doesn't + have ACL control, we will run netdata behind Nginx to get ACL control done in + Nginx.
    • +
+
[registry]
+    enabled = no
+
+[global]
+    bind to = 127.0.0.1
+    run as user = netdata
+    default port = 19999
+    update every = 3
+
+[plugin:proc]
+    # Disable IPVS check since iRedMail doesn't use ipvs by default
+    /proc/net/ip_vs/stats = no
+
+    # inbound packets dropped
+    /proc/net/dev = no
+
+ +

netdata ships a lot modular config files to gather information of softwares +running on the server, they have very good default settings and most config +files don't need your attention at all, including:

+
    +
  • System resources (CPU, RAM, disk I/O, etc)
    • +
  • Nginx log file monitoring
    • +
  • Fail2ban jails
    • +
  • Memcached
    • +
  • ...
    • +
+

But some applications do require extra settings, we will cover them below.

+

Monitor Nginx and php-fpm

+

We need to enable stub_status in Nginx to get detailed server info, also +update php-fpm config file to enable similar feature.

+
    +
  • Create Nginx config snippet /usr/local/etc/nginx/templates/stub_status.tmpl with + content below:
    • +
+
location = /stub_status {
+    stub_status on;
+    access_log off;
+    allow 127.0.0.1;
+    deny all;
+}
+
+location = /status {
+    include fastcgi_params;
+    fastcgi_pass php_workers;
+    fastcgi_param SCRIPT_FILENAME $fastcgi_script_name;
+    access_log off;
+    allow 127.0.0.1;
+    deny all;
+}
+
+ +
    +
  • Update default virtual host config file /usr/local/etc/nginx/sites-enabled/00-default.conf, + include new snippet config file stub_status.tmpl after the + redirect_to_https.tmpl line like below:
    • +
+
server {
+    ...
+    include /usr/local/etc/nginx/templates/redirect_to_https.tmpl;
+    include /usr/local/etc/nginx/templates/stub_status.tmpl;      # <- add this line
+    ...
+}
+
+ +
    +
  • Update php-fpm pool config file /usr/local/etc/php-fpm.d/www.conf, enable + parameter pm.status_path like below:
    • +
+
pm.status_path = /status
+
+ +
    +
  • Restart both php-fpm and Nginx service.
    • +
+

Monitor Dovecot

+

We need to enable statistics module in Dovecot.

+
    +
  • Please open Dovecot config file /usr/local/etc/dovecot/dovecot.conf, + append plugin stats in global parameter mail_plugins, and imap_stats + for imap protocol:
    • +
+
mail_plugins = ... stats
+
+protocol imap {
+    mail_plugins = ... imap_stats
+    ...
+}
+
+ +
    +
  • Append settings below in Dovecot config file:
    • +
+
plugin {
+    # how often to session statistics (must be set)
+    stats_refresh = 30 secs
+    # track per-IMAP command statistics (optional)
+    stats_track_cmds = yes
+}
+
+service stats {
+    fifo_listener stats-mail {
+        user = vmail
+        mode = 0644
+    }
+
+    inet_listener {
+        address = 127.0.0.1
+        port = 24242
+    }
+}
+
+ +
    +
  • Restart Dovecot service.
    • +
+

Monitor MySQL/MariaDB server

+

netdata requires a SQL user (we use netdata here) with privilege USAGE to +gather MySQL server information.

+
    +
  • Create the SQL user with a strong password (please replace <password> in + command below by the real (and strong) password).
    • +
+
# mysql -u root
+sql> GRANT USAGE ON *.* TO netdata@localhost IDENTIFIED BY '<password>';
+sql> FLUSH PRIVILEGES;
+
+ +
    +
  • +

    Create file /usr/local/etc/netdata/python.d/mysql.conf with content below.

    +
    +

    Attention

    +
      +
    • This file already exists, feel free to remove all content in this file + and copy content below as its new content.
      • +
    • Please replace <password> below by the real password.
      • +
    +
    +
    • +
+
tcp:
+    name: 'local'
+    host: '127.0.0.1'
+    port: '3306'
+    user: 'netdata'
+    pass: '<password>'
+
+ +

Monitor PostgreSQL server

+

netdata requires a SQL user (we use netdata here) to gather PostgreSQL server +information.

+
    +
  • Create the SQL user with a strong password (please replace <password> in + command below by the real (and strong) password).
    • +
+
# su - postgres
+$ psql
+sql> CREATE USER netdata WITH ENCRYPTED PASSWORD '<password>' NOSUPERUSER NOCREATEDB NOCREATEROLE;
+
+ +
    +
  • +

    Create file /usr/local/etc/netdata/python.d/mysql.conf with content below.

    +
    +

    Attention

    +
      +
    • This file already exists, feel free to remove all content in this file + and copy content below as its new content.
      • +
    • Please replace <password> below by the real password.
      • +
    +
    +
    • +
+
socket:
+    name     : 'local'
+    user     : 'netdata'
+    password : '<password>'
+    database : 'postgres'
+
+ +

Configure Nginx to forward requests to netdata

+
    +
  • Create Nginx config snippet /usr/local/etc/nginx/templates/netdata.tmpl with + content below:
    • +
+
# Running netdata as a subfolder to an existing virtual host
+# FYI: https://github.com/firehol/netdata/wiki/Running-behind-nginx
+
+location = /netdata {
+    return 301 /netdata/;
+}
+
+location ~ /netdata/(?<ndpath>.*) {
+    proxy_redirect off;
+    proxy_set_header Host $host;
+
+    proxy_set_header X-Forwarded-Host $host;
+    proxy_set_header X-Forwarded-Server $host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_http_version 1.1;
+    proxy_pass_request_headers on;
+    proxy_set_header Connection "keep-alive";
+    proxy_store off;
+    proxy_pass http://netdata/$ndpath$is_args$args;
+
+    gzip on;
+    gzip_proxied any;
+    gzip_types *;
+
+    auth_basic "Authentication Required";
+    auth_basic_user_file /usr/local/etc/nginx/netdata.users;
+}
+
+ +
    +
  • Update default virtual host (https site) config file + /usr/local/etc/nginx/sites-enabled/00-default-ssl.conf, + include new snippet config file netdata.tmpl before the + misc.tmpl line like below:
    • +
+
server {
+    ...
+    include /usr/local/etc/nginx/templates/netdata.tmpl;      # <- add this line
+    include /usr/local/etc/nginx/templates/misc.tmpl;
+    ...
+}
+
+ +
    +
  • Create new file /usr/local/etc/nginx/netdata.users and an account used to access + netdata. NOTE: Please replace <password> below by a real, strong password.
    • +
+
touch /usr/local/etc/nginx/netdata.users
+doveadm pw -s SSHA -p '<password>'
+
+ +
    +
  • Now restart nginx service and access url https://your-server/netdata/ + (please replace your-server by the real domain name).
    • +
+

All documents are available in BitBucket repository, and published under Creative Commons license. You can download the latest version for offline reading. If you found something wrong, please do contact us to fix it.

+
+ + + + \ No newline at end of file diff --git a/html/integration.netdata.linux.html b/html/integration.netdata.linux.html index 144887fd..0c443181 100644 --- a/html/integration.netdata.linux.html +++ b/html/integration.netdata.linux.html @@ -29,17 +29,20 @@
  • Monitor PostgreSQL server
    • -
  • Configure Nginx to forward requests to netdata
  • System tuning
    • +
  • Configure Nginx to forward requests to netdata

    • Attention

    -

    This tutorial is tested on CentOS 7, Debian 9, Ubuntu 16.04. -For FreeBSD, please check this tutorial instead: -Integrate netdata on FreeBSD.

    +
      +
    • This tutorial is tested on CentOS 7, Debian 9, Ubuntu 16.04. + For FreeBSD, please check this tutorial instead: + Integrate netdata on FreeBSD.
      • +
    • netdata is an optional component since iRedMail-0.9.8.
      • +

    What's netdata

    netdata (http://my-netdata.io) is a "Simple. Effective. Awesome!" monitor @@ -169,8 +172,6 @@ location = /status {

  • On RHEL/CentOS, it's /etc/php-fpm.d/www.conf
  • On Debian, it's /etc/php5/fpm/pool.d/www.conf
  • On Ubuntu, it's /etc/php/7.0/fpm/pool.d/www.conf (note: php version number may be different on your server)
    • -
  • On FreeBSD, it's /usr/local/etc/php-fpm.d/www.conf
    • -
  • On OpenBSD, it's /etc/php-fpm.conf
    • @@ -183,22 +184,15 @@ location = /status {

    Monitor Dovecot

    We need to enable statistics module in Dovecot.

      -
    • -

      Please open Dovecot config file:

      -
        -
      • on Linux and OpenBSD, its /etc/dovecot/dovecot.conf.
        • -
      • on FreeBSD, it's /usr/local/etc/dovecot/dovecot.conf.
        • -
      -
      • -
    • -

      Append plugin stats in global parameter mail_plugins, and imap_stats - for imap protocol:

      -
      • +
    • Please open Dovecot config file /etc/dovecot/dovecot.conf, append plugin + stats in global parameter mail_plugins, and imap_stats for imap protocol:
    mail_plugins = ... stats
 
 protocol imap {
     mail_plugins = ... imap_stats
+    ...
+}
      @@ -292,7 +286,6 @@ sql> CREATE USER netdata WITH ENCRYPTED PASSWORD '<password>' NOSUPERUS database : 'postgres' -

      Configure Nginx to forward requests to netdata

      System tuning

      To get better performance, netdata requires few sysctl settings. Please add lines below in /etc/sysctl.conf:

      @@ -312,7 +305,68 @@ LimitNOFILE=30000

      Reload systemd daemon:

      systemctl daemon-reload
-
      + + +

      Configure Nginx to forward requests to netdata

      +
        +
      • Create Nginx config snippet /etc/nginx/templates/netdata.tmpl with + content below:
        • +
      +
      # Running netdata as a subfolder to an existing virtual host
+# FYI: https://github.com/firehol/netdata/wiki/Running-behind-nginx
+
+location = /netdata {
+    return 301 /netdata/;
+}
+
+location ~ /netdata/(?<ndpath>.*) {
+    proxy_redirect off;
+    proxy_set_header Host $host;
+
+    proxy_set_header X-Forwarded-Host $host;
+    proxy_set_header X-Forwarded-Server $host;
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_http_version 1.1;
+    proxy_pass_request_headers on;
+    proxy_set_header Connection "keep-alive";
+    proxy_store off;
+    proxy_pass http://netdata/$ndpath$is_args$args;
+
+    gzip on;
+    gzip_proxied any;
+    gzip_types *;
+
+    auth_basic "Authentication Required";
+    auth_basic_user_file /etc/nginx/netdata.users;
+}
+
      + +
        +
      • Update default virtual host (https site) config file + /etc/nginx/sites-enabled/00-default-ssl.conf, + include new snippet config file netdata.tmpl before the + misc.tmpl line like below:
        • +
      +
      server {
+    ...
+    include /etc/nginx/templates/netdata.tmpl;      # <- add this line
+    include /etc/nginx/templates/misc.tmpl;
+    ...
+}
+
      + +
        +
      • Create new file /etc/nginx/netdata.users and an account used to access + netdata. NOTE: Please replace <password> below by a real, strong password.
        • +
      +
      touch /etc/nginx/netdata.users
+doveadm pw -s SSHA -p '<password>'
+
      + +
        +
      • Now restart nginx service and access url https://your-server/netdata/ + (please replace your-server by the real domain name).
        • +

      All documents are available in BitBucket repository, and published under Creative Commons license. You can download the latest version for offline reading. If you found something wrong, please do contact us to fix it.