Posts Tagged ‘User’

Monitoring MySQL server queries and debunning performance (slow query) issues with native MySQL commands and with mtop, mytop

Thursday, May 10th, 2012

If you're a Linux server administrator running MySQL server, you need to troubleshoot performance and bottleneck issues with the SQL database every now and then. In this article, I will pinpoint few methods to debug basic issues with MySQL database servers.

1. Troubleshooting MySQL database queries with native SQL commands

a)One way to debug errors and get general statistics is by logging in with mysql cli and check the mysql server status:

# mysql -u root -p
mysql> SHOW STATUS;
+-----------------------------------+------------+
| Variable_name | Value |
+-----------------------------------+------------+
| Aborted_clients | 1132 |
| Aborted_connects | 58 |
| Binlog_cache_disk_use | 185 |
| Binlog_cache_use | 2542 |
| Bytes_received | 115 |
.....
.....
| Com_xa_start | 0 |
| Compression | OFF |
| Connections | 150000 |
| Created_tmp_disk_tables | 0 |
| Created_tmp_files | 221 |
| Created_tmp_tables | 1 |
| Delayed_errors | 0 |
| Delayed_insert_threads | 0 |
| Delayed_writes | 0 |
| Flush_commands | 1 |
.....
.....
| Handler_write | 132 |
| Innodb_page_size | 16384 |
| Innodb_pages_created | 6204 |
| Innodb_pages_read | 8859 |
| Innodb_pages_written | 21931 |
.....
.....
| Slave_running | OFF |
| Slow_launch_threads | 0 |
| Slow_queries | 0 |
| Sort_merge_passes | 0 |
| Sort_range | 0 |
| Sort_rows | 0 |
| Sort_scan | 0 |
| Table_locks_immediate | 4065218 |
| Table_locks_waited | 196 |
| Tc_log_max_pages_used | 0 |
| Tc_log_page_size | 0 |
| Tc_log_page_waits | 0 |
| Threads_cached | 51 |
| Threads_connected | 1 |
| Threads_created | 52 |
| Threads_running | 1 |
| Uptime | 334856 |
+-----------------------------------+------------+
225 rows in set (0.00 sec)

SHOW STATUS; command gives plenty of useful info, however it is not showing the exact list of queries currently processed by the SQL server. Therefore sometimes it is exactly a stucked (slow queries) execution, you need to debug in order to fix a lagging SQL. One way to track this slow queries is via enabling mysql slow-query.log. Anyways enabling the slow-query requires a MySQL server restart and some critical productive database servers are not so easy to restart and the SQL slow queries have to be tracked "on the fly" so to say.
Therefore, to check the exact (slow) queries processed by the SQL server (without restarting it), do
 

mysql> SHOW processlist;
+——+——+—————+——+———+——+————–+——————————————————————————————————+
| Id | User | Host | db | Command | Time | State | Info |
+——+——+—————+——+———+——+————–+——————————————————————————————————+
| 609 | root | localhost | blog | Sleep | 5 | | NULL |
| 1258 | root | localhost | NULL | Sleep | 85 | | NULL |
| 1308 | root | localhost | NULL | Query | 0 | NULL | show processlist |
| 1310 | blog | pcfreak:64033 | blog | Query | 0 | Sending data | SELECT comment_author, comment_author_url, comment_content, comment_post_ID, comment_ID, comment_aut |
+——+——+—————+——+———+——+————–+——————————————————————————————————+
4 rows in set (0.00 sec)
mysql>

SHOW processlist gives a good view on what is happening inside the SQL.

To get more complete information on SQL query threads use the full extra option:

mysql> SHOW full processlist;

This gives pretty full info on running threads, but unfortunately it is annoying to re-run the command again and again – constantly to press UP Arrow + Enter keys.

Hence it is useful to get the same command output, refresh periodically every few seconds. This is possible by running it through the watch command:

debian:~# watch "'show processlist' | mysql -u root -p'secret_password'"

watch will run SHOW processlist every 2 secs (this is default watch refresh time, for other timing use watch -n 1, watch -n 10 etc. etc.

The produced output will be similar to:

Every 2.0s: echo 'show processlist' | mysql -u root -p'secret_password' Thu May 10 17:24:19 2012

Id User Host db Command Time State Info
609 root localhost blog Sleep 3 NULL1258 root localhost NULL Sleep 649 NULL1542 blog pcfreak:64981 blog Query 0 Copying to tmp table \
SELECT p.ID, p.post_title, p.post_content,p.post_excerpt, p.pos
t_date, p.comment_count, count(t_r.o
1543 root localhost NULL Query 0 NULL show processlist

Though this "hack" is one of the possible ways to get some interactivity on what is happening inside SQL server databases and tables table. for administering hundred or thousand SQL servers running dozens of queries per second – monitor their behaviour few times aday using mytop or mtop is times easier.

Though, the names of the two tools are quite similar and I used to think both tools are one and the same, actually they're not but both are suitable for monitoring sql database execution in real time.

As a sys admin, I've used mytop and mtop, on almost each Linux server with MySQL server installed.
Both tools has helped me many times in debugging oddities with sql servers. Therefore my personal view is mytop and mtop should be along with the Linux sysadmin most useful command tools outfit, still I'm sure many administrators still haven't heard about this nice goodies.

1. Installing mytop on Debian, Ubuntu and other deb based GNU / Linux-es

mytop is available for easy install on Debian and across all debian / ubuntu and deb derivative distributions via apt.

Here is info obtained with apt-cache show

debian:~# apt-cache show mytop|grep -i description -A 3
Description: top like query monitor for MySQL
Mytop is a console-based tool for monitoring queries and the performance
of MySQL. It supports version 3.22.x, 3.23.x, 4.x and 5.x servers.
It's written in Perl and support connections using TCP/IP and UNIX sockets.

Installing the tool is done with the trivial:

debian:~# apt-get --yes install mytop
....

mtop used to be available for apt-get-ting in Debian Lenny and prior Debian releases but in Squeeze onwards, only mytop is included (probably due to some licensing incompitabilities with mtop??).

For those curious on how mtop / mytop works – both are perl scripts written to periodically connects to the SQL server and run commands similar to SHOW FULL PROCESSLIST;. Then, the output is parsed and displayed to the user.

Here how mytop running, looks like:

MyTOP showing queries running on Ubuntu 8.04 Linux - Debugging interactively top like MySQL

2. Installing mytop on RHEL and CentOS

By default in RHEL and CentOS and probably other RedHat based Linux-es, there is neither mtop nor mytop available in package repositories. Hence installing the tools on those is only available from 3rd parties. As of time of writting an rpm builds for RHEL and CentOS, as well as (universal rpm distros) src.rpm package is available on http://pkgs.repoforge.org/mytop/. For the sake of preservation – if in future those RPMs disappear, I made a mirror of mytop rpm's here

Mytop rpm builds depend on a package perl(Term::ReadKey), my attempt to install it on CentOS 5.6, returned following err:

[root@cenots ~]# rpm -ivh mytop-1.4-2.el5.rf.noarch.rpm
warning: mytop-1.4-2.el5.rf.noarch.rpm: Header V3 DSA signature: NOKEY, key ID 6b8d79e6
error: Failed dependencies:
perl(Term::ReadKey) is needed by mytop-1.4-2.el5.rf.noarch

The perl(Term::ReadKey package is not available in CentOS 5.6 and (probably other centos releases default repositories so I had to google perl(Term::ReadKey) I found it on http://rpm.pbone.net/ package repository, the exact url to the rpm dependency as of time of writting this post is:

ftp://ftp.pbone.net/mirror/yum.trixbox.org/centos/5/old/perl-Term-ReadKey-2.30-2.rf.i386.rpm

Quickest, way to install it is:

[root@centos ~]# rpm -ivh ftp://ftp.pbone.net/mirror/yum.trixbox.org/centos/5/old/perl-Term-ReadKey-2.30-2.rf.i386.rpmRetrieving ftp://ftp.pbone.net/mirror/yum.trixbox.org/centos/5/old/perl-Term-ReadKey-2.30-2.rf.i386.rpmPreparing... ########################################### [100%]
1:perl-Term-ReadKey ########################################### [100%]

This time mytop, install went fine:

[root@centos ~]# rpm -ivh mytop-1.4-2.el5.rf.noarch.rpm
warning: mytop-1.4-2.el5.rf.noarch.rpm: Header V3 DSA signature: NOKEY, key ID 6b8d79e6
Preparing... ########################################### [100%]
1:mytop ########################################### [100%]

To use it further, it is the usual syntax:

mytop -u username -p 'secret_password' -d database

CentOS Linux MyTOP MySQL query benchmark screenshot - vpopmail query

3. Installing mytop and mtop on FreeBSD and other BSDs

To debug the running SQL queries in a MySQL server running on FreeBSD, one could use both mytop and mtop – both are installable via ports:

a) To install mtop exec:

freebsd# cd /usr/ports/sysutils/mtop
freebsd# make install clean
....

b) To install mytop exec:

freebsd# cd /usr/ports/databases/mytop
freebsd# make install clean
....

I personally prefer to use mtop on FreeBSD, because once run it runs prompts the user to interactively type in the user/pass

freebsd# mtop

Then mtop prompts the user with "interactive" dialog screen to type in user and pass:

Mtop interactive type in username and password screenshot on FreeBSD 7.2

It is pretty annoying, same mtop like syntax don't show user/pass prompt:

freebsd# mytop
Cannot connect to MySQL server. Please check the:

* database you specified "test" (default is "test")
* username you specified "root" (default is "root")
* password you specified "" (default is "")
* hostname you specified "localhost" (default is "localhost")
* port you specified "3306" (default is 3306)
* socket you specified "" (default is "")
The options my be specified on the command-line or in a ~/.mytop
config file. See the manual (perldoc mytop) for details.
Here's the exact error from DBI. It might help you debug:
Unknown database 'test'

The correct syntax to run mytop instead is:

freebsd# mytop -u root -p 'secret_password' -d 'blog'

Or the longer more descriptive:

freebsd# mytop --user root --pass 'secret_password' --database 'blog'

By the way if you take a look at mytop's manual you will notice a tiny error in documentation, where the three options –user, –pass and –database are wrongly said to be used as -user, -pass, -database:

freebsd# mytop -user root -pass 'secret_password' -database 'blog'
Cannot connect to MySQL server. Please check the:

* database you specified "atabase" (default is "test")
* username you specified "ser" (default is "root")
* password you specified "ass" (default is "")
* hostname you specified "localhost" (default is "localhost")
* port you specified "3306" (default is 3306)
* socket you specified "" (default is "")a
...
Access denied for user 'ser'@'localhost' (using password: YES)

Actually it is interesting mytop, precededed historically mtop.
mtop was later written (probably based on mytop), to run on FreeBSD OS by a famous MySQL (IT) spec — Jeremy Zawodny .
Anyone who has to do frequent MySQL administration tasks, should already heard Zawodny's name.
For those who haven't, Jeremy used to be a head database administrators and developer in Yahoo! Inc. some few years ago.
His website contains plenty of interesting thoughts and writtings on MySQL server and database management
 

How to check MASTER / SLAVE MySQL nodes status – Check MySQL Replication Status

Thursday, April 19th, 2012

I'm doing replication for one server. Its not the first time I do configure replication between two MySQL database nodes, however since I haven't done it for a few years, my "know how" has mostly vanished so I had some troubles in setting it up. Once I followed some steps to configure replication I had to check if the two MASTER / Slave MySQL db nodes communicate properly. Hence I decided to drop a short post on that just in case if someone has to do the same or if I myself forget how I did it so I can check later on:

1. Check if MASTER MySQL server node is configured properly

The standard way to check a MySQL master node status info is with:
 

mysql> show master status;
+——————+———-+———————————————————+——————+
| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |
+——————+———-+———————————————————+——————+
| mysql-bin.000007 | 106 | database1,database2,database3 | |
+——————+———-+———————————————————+——————+
1 row in set (0.00 sec)

By putting \G some extra status info is provided:
 

mysql> show master status\G;
*************************** 1. row ***************************
File: mysql-bin.000007
Position: 106
Binlog_Do_DB: database1,database2,database3
Binlog_Ignore_DB:
1 row in set (0.00 sec)

ERROR:
No query specified

2. Check if Slave MySQL node is configured properly

To check status of the slave the cmd is:
 

mysql> show slave status;

The command returns an output like:
 

mysql> show slave status;+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+| Slave_IO_State | Master_Host | Master_User | Master_Port | Connect_Retry | Master_Log_File | Read_Master_Log_Pos | Relay_Log_File | Relay_Log_Pos | Relay_Master_Log_File | Slave_IO_Running | Slave_SQL_Running | Replicate_Do_DB | Replicate_Ignore_DB | Replicate_Do_Table | Replicate_Ignore_Table | Replicate_Wild_Do_Table | Replicate_Wild_Ignore_Table | Last_Errno | Last_Error | Skip_Counter | Exec_Master_Log_Pos | Relay_Log_Space | Until_Condition | Until_Log_File | Until_Log_Pos | Master_SSL_Allowed | Master_SSL_CA_File | Master_SSL_CA_Path | Master_SSL_Cert | Master_SSL_Cipher | Master_SSL_Key | Seconds_Behind_Master | Master_SSL_Verify_Server_Cert | Last_IO_Errno | Last_IO_Error | Last_SQL_Errno | Last_SQL_Error |+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+| Waiting for master to send event | HOST_NAME.COM | slave_user | 3306 | 10 | mysql-bin.000007 | 106 | mysqld-relay-bin.000002 | 251 | mysql-bin.000007 | Yes | Yes | database1,database2,database3 | | | | | | 0 | | 0 | 106 | 407 | None | | 0 | No | | | | | | 0 | No | 0 | | 0 | |+———————————-+————-+————-+————-+—————+——————+———————+————————-+—————+———————–+——————+——————-+——————————————————-+———————+——————–+————————+————————-+—————————–+————+————+————–+———————+—————–+—————–+—————-+—————+——————–+——————–+——————–+—————–+——————-+—————-+———————–+——————————-+—————+—————+—————-+—————-+

As you can see the output is not too readable, as there are too many columns and data to be displayed and this doesn't fit neither a text console nor a graphical terminal emulator.

To get more readable (more verbose) status for the SQL SLAVE, its better to use command:
 

mysql> show slave status\G;

Here is a sample returned output:
 

mysql> show slave status\G;*************************** 1. row *************************** Slave_IO_State: Waiting for master to send event Master_Host: HOST_NAME.COM Master_User: slave_user Master_Port: 3306 Connect_Retry: 10 Master_Log_File: mysql-bin.000007 Read_Master_Log_Pos: 106 Relay_Log_File: mysqld-relay-bin.000002 Relay_Log_Pos: 251 Relay_Master_Log_File: mysql-bin.000007 Slave_IO_Running: Yes Slave_SQL_Running: Yes Replicate_Do_DB: database1,database2,database3 Replicate_Ignore_DB: Replicate_Do_Table: Replicate_Ignore_Table: Replicate_Wild_Do_Table: Replicate_Wild_Ignore_Table: Last_Errno: 0 Last_Error: Skip_Counter: 0 Exec_Master_Log_Pos: 106 Relay_Log_Space: 407 Until_Condition: None Until_Log_File: Until_Log_Pos: 0 Master_SSL_Allowed: No Master_SSL_CA_File: Master_SSL_CA_Path: Master_SSL_Cert: Master_SSL_Cipher: Master_SSL_Key: Seconds_Behind_Master: 0Master_SSL_Verify_Server_Cert: No Last_IO_Errno: 0 Last_IO_Error: Last_SQL_Errno: 0 Last_SQL_Error: 1 row in set (0.00 sec)ERROR: No query specified

If show master status or shwo slave status commands didn't reveal replication issue, one needs to stare at the mysql log for more info.

Tiny PHP script to dump your browser set HTTP headers (useful in debugging)

Friday, March 30th, 2012

While browsing I stumbled upon a nice blog article

Dumping HTTP headers

The arcitle, points at few ways to DUMP the HTTP headers obtained from user browser.
As I'm not proficient with Ruby, Java and AOL Server what catched my attention is a tiny php for loop, which loops through all the HTTP_* browser set variables and prints them out. Here is the PHP script code:

<?php<br />
foreach($_SERVER as $h=>$v)<br />
if(ereg('HTTP_(.+)',$h,$hp))<br />
echo "<li>$h = $v</li>\n";<br />
header('Content-type: text/html');<br />
?>

The script is pretty easy to use, just place it in a directory on a WebServer capable of executing php and save it under a name like:
show_HTTP_headers.php

If you don't want to bother copy pasting above code, you can also download the dump_HTTP_headers.php script here , rename the dump_HTTP_headers.php.txt to dump_HTTP_headers.php and you're ready to go.

Follow to the respective url to exec the script. I've installed the script on my webserver, so if you are curious of the output the script will be returning check your own browser HTTP set values by clicking here.
PHP will produce output like the one in the screenshot you see below, the shot is taken from my Opera browser:

Screenshot show HTTP headers.php script Opera Debian Linux

Another sample of the text output the script produce whilst invoked in my Epiphany GNOME browser is:

HTTP_HOST = www.pc-freak.net
HTTP_USER_AGENT = Mozilla/5.0 (X11; U; Linux x86_64; en-us) AppleWebKit/531.2+ (KHTML, like Gecko) Version/5.0 Safari/531.2+ Debian/squeeze (2.30.6-1) Epiphany/2.30.6
HTTP_ACCEPT = application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
HTTP_ACCEPT_ENCODING = gzip
HTTP_ACCEPT_LANGUAGE = en-us, en;q=0.90
HTTP_COOKIE = __qca=P0-2141911651-1294433424320;
__utma_a2a=8614995036.1305562814.1274005888.1319809825.1320152237.2021;wooMeta=MzMxJjMyOCY1NTcmODU1MDMmMTMwODQyNDA1MDUyNCYxMzI4MjcwNjk0ODc0JiYxMDAmJjImJiYm; 3ec0a0ded7adebfeauth=22770a75911b9fb92360ec8b9cf586c9;
__unam=56cea60-12ed86f16c4-3ee02a99-3019;
__utma=238407297.1677217909.1260789806.1333014220.1333023753.1606;
__utmb=238407297.1.10.1333023754; __utmc=238407297;
__utmz=238407297.1332444980.1586.413.utmcsr=pc-freak.net|utmccn=(referral)|utmcmd=referral|utmcct=/blog/

You see the script returns, plenty of useful information for debugging purposes:
HTTP_HOST – Virtual Host Webserver name
HTTP_USER_AGENT – The browser exact type useragent returnedHTTP_ACCEPT – the type of MIME applications accepted by the WebServerHTTP_ACCEPT_LANGUAGE – The language types the browser has support for
HTTP_ACCEPT_ENCODING – This PHP variable is usually set to gzip or deflate by the browser if the browser has support for webserver returned content gzipping.
If HTTP_ACCEPT_ENCODING is there, then this means remote webserver is configured to return its HTML and static files in gzipped form.
HTTP_COOKIE – Information about browser cookies, this info can be used for XSS attacks etc. 🙂
HTTP_COOKIE also contains the referrar which in the above case is:
__utmz=238407297.1332444980.1586.413.utmcsr=pc-freak.net|utmccn=(referral)
The Cookie information HTTP var also contains information of the exact link referrar:
|utmcmd=referral|utmcct=/blog/

For the sake of comparison show_HTTP_headers.php script output from elinks text browser is like so:

* HTTP_HOST = www.pc-freak.net
* HTTP_USER_AGENT = Links (2.3pre1; Linux 2.6.32-5-amd64 x86_64; 143x42)
* HTTP_ACCEPT = */*
* HTTP_ACCEPT_ENCODING = gzip,deflate * HTTP_ACCEPT_CHARSET = us-ascii, ISO-8859-1, ISO-8859-2, ISO-8859-3, ISO-8859-4, ISO-8859-5, ISO-8859-6, ISO-8859-7, ISO-8859-8, ISO-8859-9, ISO-8859-10, ISO-8859-13, ISO-8859-14, ISO-8859-15, ISO-8859-16, windows-1250, windows-1251, windows-1252, windows-1256,
windows-1257, cp437, cp737, cp850, cp852, cp866, x-cp866-u, x-mac, x-mac-ce, x-kam-cs, koi8-r, koi8-u, koi8-ru, TCVN-5712, VISCII,utf-8 * HTTP_ACCEPT_LANGUAGE = en,*;q=0.1
* HTTP_CONNECTION = keep-alive
One good reason, why it is good to give this script a run is cause it can help you reveal problems with HTTP headers impoperly set cookies, language encoding problems, security holes etc. Also the script is a good example, for starters in learning PHP programming.

 

Check and Restart Apache if it is malfunctioning (not returning HTML content) shell script

Monday, March 19th, 2012

Check and Restart Apache Webserver on Malfunction, Apache feather logo

One of the company Debian Lenny 5.0 Webservers, where I'm working as sys admin sometimes stops to properly server HTTP requests.
Whenever this oddity happens, the Apache server seems to be running okay but it is not failing to return requested content

I can see the webserver listens on port 80 and establishing connections to remote hosts – the apache processes show normally as I can see in netstat …:

apache:~# netstat -enp 80
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address Foreign Address State User Inode PID/Program name
tcp 0 0 xxx.xxx.xxx.xx:80 46.253.9.36:5665 SYN_RECV 0 0 -
tcp 0 0 xxx.xxx.xxx.xx:80 78.157.26.24:5933 SYN_RECV 0 0 -
...

Also the apache forked child processes show normally in process list:

apache:~# ps axuwwf|grep -i apache
root 46748 0.0 0.0 112300 872 pts/1 S+ 18:07 0:00 \_ grep -i apache
root 42530 0.0 0.1 217392 6636 ? Ss Mar14 0:39 /usr/sbin/apache2 -k start
www-data 42535 0.0 0.0 147876 1488 ? S Mar14 0:01 \_ /usr/sbin/apache2 -k start
root 28747 0.0 0.1 218180 4792 ? Sl Mar14 0:00 \_ /usr/sbin/apache2 -k start
www-data 31787 0.0 0.1 219156 5832 ? S Mar14 0:00 | \_ /usr/sbin/apache2 -k start

In spite of that, in any client browser to any of the Apache (Virtual hosts) websites, there is no HTML content returned…
This weird problem continues until the Apache webserver is retarted.
Once webserver is restarted everything is back to normal.
I use Apache Check Apache shell script set on few remote hosts to regularly check with nmap if port 80 (www) of my server is open and responding, anyways this script just checks if the open and reachable and thus using it was unable to detect Apache wasn't able to return back HTML content.
To work around the malfunctions I wrote tiny script – retart_apache_if_empty_content_is_returned.sh

The scripts idea is very simple;
A request is made a remote defined host with lynx text browser, then the output of lines is counted, if the output returned by lynx -dump http://someurl.com is less than the number returned whether normally invoked, then the script triggers an apache init script restart.

I've set the script to periodically run in a cron job, every 5 minutes each hour.
# check if apache returns empty content with lynx and if yes restart and log it
*/5 * * * * /usr/sbin/restart_apache_if_empty_content.sh >/dev/null 2>&1

This is not perfect as sometimes still, there will be few minutes downtime, but at least the downside will not be few hours until I am informed ssh to the server and restart Apache manually

A quick way to download and set from cron execution my script every 5 minutes use:

apache:~# cd /usr/sbin
apache:/usr/sbin# wget -q http://www.pc-freak.net/bscscr/restart_apache_if_empty_content.sh
apache:/usr/sbin# chmod +x restart_apache_if_empty_content.sh
apache:/usr/sbin# crontab -l > /tmp/file; echo '*/5 * * * *' /usr/sbin/restart_apache_if_empty_content.sh 2>&1 >/dev/null

 

How to make wordpress Update Plugins prompt to permanently store password / Get rid of annoying updates wordpress prompt

Thursday, February 2nd, 2012

I'm managing few wordpress installations which requires me to type in:
Hostname , FTP Username and FTP Password , every single time a plugin update is issued and I want to upgrade to the new version.
Below is a screenshot of this annoying behaviour:

How to get rid of update plugins wordpress username password prompt

As you can see in the above screenshot, there is no way through Update Plugins web interface to store the password permanently. Hence the only option to store it permanently is to manually edit wp-config.php (file located in wordpress docroot, e.g. /path/to/wordpress/wp-config.php , inside the file find the line:

define ('WPLANG', '');

Right after it put a code similar to:

define('FS_METHOD', 'ftpsockets');
define('FTP_BASE', '/path/to/wordpress/');
define('FTP_CONTENT_DIR', '/path/to/wordpress/wp-content/');
define('FTP_PLUGIN_DIR ', '/path/to/wordpress/wp-content/plugins/');
define('FTP_USER', 'Username');
define('FTP_PASS', 'Password');
define('FTP_HOST', 'localhost');

Change the above defines:
path/to/wordpress/ – with your wordpress location directory.
Username and Password – with your respective FTP username and password. The localhost

That's all, from now onwards the User/Password prompt will not appear anymore. Consider there is a security downside of storing the FTP User/Pass in wp-config.php , if someone is able to intrude the wordpress install and access the documentroot of the wordpress install he we'll be able to obtain the ftp user/pass and log in the server directly via FTP protocol.

How to set applications (programs) Autorun on XFCE in Xubuntu Linux

Monday, January 16th, 2012

I needed to set TeamViewer to autorun, each and every startup on one Xubuntu Linux

Xubuntu is running by default with Xfce 4 . Xfce is a sort of a very liteweight GNOME like graphical environment.

In Gnome the way that is through invoking the gnome-session-manager .

In Xfce the command is almost analogous doing changes is done by running:

user@xubuntu:~$ xfce4-session-manager

XFce session manager Xubuntu Linux screenshot
Further on simply use the Add button to add applications to load each time user (opens xfce session) / logs in.
Cheers 😉

How to install and configure Jabber Server (Ejabberd) on Debian Lenny GNU / Linux

Wednesday, December 28th, 2011

Ejabberd server erlang logo hedgehog

I've recently installed a jabber server on one Debian Lenny server and hence decided to describe my installations steps hoping this would help ppl who would like to run their own jabber server on Debian . After some research of the jabber server softwares available, I decided to install Ejabberd

The reasons I choose Ejabberd is has rich documentation, good community around the project and the project in general looks like one of the best free software jabber servers available presently. Besides that ejabberd doesn't need Apache or MySQL and only depends on erlang programming language.

Here is the exact steps I followed to have installed and configured a running XMPP jabber server.

1. Install Ejabberd with apt

The installation of Ejabberd is standard, e.g.:

debian:~# apt-get --yes install ejabberd

Now as ejabberd is installed, some minor configuration is necessery before the server can be launched:

2. Edit /etc/ejabberd/ejabberd.cfg

Inside I changed the default settings for:

a) Uncomment%%override_acls.. Changed:

%%%% Remove the Access Control Lists before new ones are added.%%%%override_acls.

to

%%
%% Remove the Access Control Lists before new ones are added.
%%
override_acls.

b) Admin User from:

%% Admin user
{acl, admin, {user, "", "example.com"}}.

to

%% Admin user
{acl, admin, {user, "admin", "jabber.myserver-host.com"}}.

c) default %% Hostname of example.com to my real hostname:

%% Hostname
{hosts, ["jabber.myserver-host.com"]}.

The rest of the configurations in /etc/ejabberd/ejabberd.cfg can stay like it is, though it is interesting to read it carefully before continuing as, there are some config timings which might prevent the XMPP server from user brute force attacks as well as few other goodies like for example (ICQ, MSN , Yahoo etc.) protocol transports.

3. Add iptables ACCEPT traffic (allow) rules for ports which are used by Ejabberd

The minimum ACCEPT rules to add are:

/sbin/iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 5222 -j ACCEPT
/sbin/iptables -A INPUT -p udp -m udp --dport 5222 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 5223 -j ACCEPT
/sbin/iptables -A INPUT -p udp -m udp --dport 5223 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 5269 -j ACCEPT
/sbin/iptables -A INPUT -p udp -m udp --dport 5269 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 5280 -j ACCEPT
/sbin/iptables -A INPUT -p udp -m udp --dport 5280 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 4369 -j ACCEPT
/sbin/iptables -A INPUT -p udp -m udp --dport 4369 -j ACCEPT
/sbin/iptables -A INPUT -p tcp -m tcp --dport 53873 -j ACCEPT

Of course if there is some specific file which stores iptables rules or some custom firewall these rules has to be added / modified to fit appropriate place or chain.

4. Restart ejabberd via init.d script

debian:~# /etc/init.d/ejabberd restart
Restarting jabber server: ejabberd is not running. Starting ejabberd.

5. Create ejabberd necessery new user accounts

debian:~# /usr/sbin/ejabberdctl register admin jabber.myserver-host.com mypasswd1
debian:~# /usr/sbin/ejabberdctl register hipo jabber.myserver-host.com mypasswd2
debian:~# /usr/sbin/ejabberdctl register newuser jabber.myserver-host.com mypasswd3
debian:~# /usr/sbin/ejabberdctl register newuser1 jabber.myserver-host.com mypasswd4
...
etc.

ejabberdctl ejabberd server client (frontend) has multiple other options and the manual is a good reading.

One helpful use of ejabberdctl is:

debian:~# /usr/sbin/ejabberdctl status
Node ejabberd@debian is started. Status: started
ejabberd is running

ejabberctl can be used also to delete some existent users, for example to delete the newuser1 just added above:

debian:~# /usr/sbin/ejabberdctl unregister newuser jabber.myserver-host.com

6. Post install web configurations

ejabberd server offers a web interface listening on port 5280, to access the web interface right after it is installed I used URL: http://jabber.myserver-host.com:5280/admin/

To login to http://jabber.myserver-host.com:5280/admin/ you will need to use the admin username previously added in this case:
admin@jabber.myserver-host.com mypasswd1

Anyways in the web interface there is not much of configuration options available for change.

7. Set dns SRV records

I'm using Godaddy 's DNS for my domain so here is a screenshot on the SRV records that needs to be configured on Godaddy:

GoDaddy DNS SRV records screenshot

In the screenshto Target is the Fually qualified domain hostname for the jabber server.

Setting the SRV records for the domain using Godaddy's DNS could take from 24 to 48 hours to propagate the changes among all the global DNS records so be patient.

If instead you use own custom BIND DNS server the records that needs to be added to the respective domain zone file are:

_xmpp-client._tcp 900 IN SRV 5 0 5222 jabber.myserver-host.com.
_xmpp-server._tcp 900 IN SRV 5 0 5269 jabber.myserver-host.com.
_jabber._tcp 900 IN SRV 5 0 5269 jabber.myserver-host.com.

8. Testing if the SRV dns records for domain are correct

debian:~$ nslookup
> set type=SRV
> jabber.myserver-host.com
 ...
> myserver-host.com

 If all is fine above nslookup request should return the requested domain SRV records.
You might be wondering what is the purpose of setting DNS SRV records at all, well if your jabber server has to communicate with the other jabber servers on the internet using the DNS SRV record is the way your server will found the other ones and vice versa.

DNS records can also be checked with dig for example

$ dig SRV _xmpp-server._tcp.mydomain.net

[…]

;; QUESTION SECTION:
;_xmpp-server._tcp.mydomain.net. IN SRV

;; ANSWER SECTION:
_xmpp-server._tcp.mydomain.net. 259200 IN SRV 5 0 5269 jabber.mydomain.net.

;; ADDITIONAL SECTION:
jabber.mydomain.net. 259200 IN A 11.22.33.44

;; Query time: 109 msec
;; SERVER: 212.27.40.241#53(212.27.40.241)
;; WHEN: Sat Aug 14 14:14:22 2010
;; MSG SIZE rcvd: 111

9. Debugging issues with ejabberd

Ejabberd log files are located in /var/log/ejabberd , you will have to check the logs in case of any issues with the jabber XMPP server. Here is the three files which log messages from ejabberd:

debian:~$ ls -1 /var/log/ejabberd/
ejabberd.log
erl_crash.dump
sasl.log

I will not get into details on the logs as the best way to find out about them is to read them 😉

10. Testing ejabberd server with Pidgin

To test if my Jabber server works properly I used Pidgin universal chat client . However there are plenty of other multiplatform jabber clients out there e.g.: Psi , Spark , Gajim etc.

Here is a screenshot of my (Accounts -> Manage Accounts -> Add) XMPP protocol configuration

Pidgin account configuration XMPP on debian Linux
 

How to convert AVI, MP4, FLV (flash video) and other non-free video encoded formats to Free Video format encoding OGV (Ogg Vorbis / Theora) on GNU / Linux and FreeBSD

Thursday, November 17th, 2011

Ogg Vorbis Free / Open Audio Video Format logo

I was looking for a way to convert some Video and Sound files, downloaded from Youtube (mostly things dedicated to free software) and as far as I looked online unfortunately these pieces of nice music and tutorials are not available for download anywhere else or at least not available for download in some of the Open / Free Format (OGG Vorbis or OGV (OGG / Theora Video).

When it comes to convertion between different formats, always the first things that I think of is ffmpeg or mencoder , however I was not sure if some of this tools are doing the trick so I did a quick research online if there is some specialised console or GUI program that can do the convertions between MP4, FLV etc. to OGV.

In less than 10 minutes I found a threat mentioning about ffmpeg2theoraA Simple Convertor to create Ogg Theora files

As I’m running Debian GNU / Linux, I installed ffmpeg2theora straight via apt, according to some reports online ffmpeg2theora cmd convertion tool is also available straight from repositories on Ubuntu as well.
On FreeBSD there is a port /usr/ports/multimedia/ffmpeg2theora available for install. Of course FFmpeg2Theora can be installed from source on other Linux distributions that might be missing a pre-built binary.

Using ffmpeg2theora to convert some kind of non-free video format is very simple, though the tool provides quite a numerous options for all those who want to have some customization for the video to be converted.
To convert the flash file “The Gnu Song.flv” for example to The Gnu Song.flv , I invoked ffmpeg2theora like this:

debian:~# ffmpeg2theora "The Gnu Song.flv"
...

The conversion took few minutes of time, as my machine is not ultra powerful and apparently the conversion to OGV format is not too quick but the good news is it works.
After the conversion was completed I used ogginfo to check the information about the recent converted file The Gnu Song.flv , below you see the file info ogginfo returns

debian:~# ogginfo The Gnu Song.ogv
Processing file "The Gnu Song.ogv"...

New logical stream (#1, serial: 5d65413f): type skeleton
New logical stream (#2, serial: 0570412d): type theora
New logical stream (#3, serial: 7e679651): type vorbis
Theora headers parsed for stream 2, information follows…
Version: 3.2.1
Vendor: Xiph.Org libtheora 1.1 20090822 (Thusnelda)
Width: 320
Height: 240
Total image: 320 by 240, crop offset (0, 0)
Framerate 25/1 (25.00 fps)
Aspect ratio undefined
Colourspace: Rec. ITU-R BT.470-6 Systems B and G (PAL)
Pixel format 4:2:0
Target bitrate: 0 kbps
Nominal quality setting (0-63): 32
User comments section follows…
ENCODER=ffmpeg2theora-0.24
Vorbis headers parsed for stream 3, information follows…
Version: 0
Vendor: Xiph.Org libVorbis I 20101101 (Schaufenugget)
Channels: 1
Rate: 22050
Nominal bitrate: 30.444000 kb/s
Upper bitrate not set
Lower bitrate not set
User comments section follows…
ENCODER=ffmpeg2theora-0.24
Logical stream 1 ended
Theora stream 2:
Total data length: 1525324 bytes
Playback length: 2m:41.360s
Average bitrate: 75.623401 kb/s
Logical stream 2 ended
Vorbis stream 3:
Total data length: 646729 bytes
Playback length: 2m:41.384s
Average bitrate: 32.059041 kb/s

ogginfo is a part of a package installed under the name vorbis-tools, vorbis tools also contains a few other helpful tools, whether operations with OGV or OGG file formats are at hand, the complete binaries vorbis-tools contains on Debian as of time of writting this post is:

/usr/bin/ogg123
/usr/bin/oggenc
/usr/bin/oggdec
/usr/bin/ogginfo
/usr/bin/vcut
/usr/bin/vorbiscomment
/usr/bin/vorbistagedit

ogg123 is a player for ogg files, however as far as I’ve tested it it doesn’t work too well. And just to compare ogg audio files were played just nice using the play command.
oggenc is used to encode ogg audio file, based on a stream haneded to it from other audio encoded stream (let’s say mp3). Hence oggenc can be used to convert mp3 files to ogg audio files , like so:

debian:~# mpg321 input.mp3 -w - | oggenc -o output.ogg -

oggdec is used to convert to wav files or raw PCM audio, whether;
vcut is used to cut ogg video file on parts.
vorbiscomment and vorbistagedit is used to edit information on already existing ogg audio files

There is also a GUI programmer for people who doesn’t want to bother with writting on the command line called oggconvert . OggConvert is written for GNOME and uses GTK gnome library, here is how the program looks like:

OggConvert GUI Program to convert to OGG og OGV Theora on GNU / Linux and FreeBSD

 

How to add a new MySQL user to have INSERT,UPDATE,DELETE permissions to a Database

Tuesday, October 25th, 2011

I needed to add a newly created MySQL user with no access to any database with no special permissions (user is created from phpmyadmin) with some permissions to a specific database which is used for the operation of a website, here are the MySQL CLI client commands I issued to make it work:

# mysql -u root -p
mysql> GRANT ALL ON Sql_User_DB.* TO Sql_User@localhost;
mysql> FLUSH PRIVILEGES;

Where in the Example Sql_User_DB is my example database to which the user is granted access and my sample user is Sql_User .
Note that without FLUSH PRIVILEGES; new privileges might not be active. 

To test further if all is fine login with Sql_User and try to list database tables.

$ mysql -u Sql_User -p
password:
mysql> USE Sql_User_DB;
mysql> SHOW TABLES;
...