Posts Tagged ‘pcfreak’

How to determine which processes make most writes on the hard drive in GNU / Linux using kernel variable

Thursday, November 13th, 2014

how-to-determine-which-processes-writes-most-to-hard-drive-Linux-Kernel
In Linux there are plenty of tools to measure input / ouput – read / write server bottlenecks. Just to mention a few such are, the native part of all Linux distributions IOSTAT – which is a great tool to measure hard disk bottlenecks. However as iostat requires certain sysadmin skills for novice sys-admins, there is also ofcourse more interactive tools such as DSTAT or even better GLANCE which monitors not only disk writes but memory use, CPU load and Network use.

This tools can help you measure which processes are writting most (a lot) to hard disk drive but there is another quick and efficient way to track disk i/o by directly using the Linux kernel this is done via kernel parameter :

/proc/sys/vm/block_dump

To enable block_dump kernel logging:

echo 1 > /proc/sys/vm/block_dump

To later track in real time output from kernel interactively on which running process calling the kernel is writing to server hard drive
 

tail -f /var/log/syslog

The output  looks like so:
 

Nov 13 12:25:51 pcfreak kernel: [1075037.701056] kjournald(297): WRITE block 482293496 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.701059] kjournald(297): WRITE block 482293504 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.701062] kjournald(297): WRITE block 482293512 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.701066] kjournald(297): WRITE block 482293520 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.701069] kjournald(297): WRITE block 482293528 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.701072] kjournald(297): WRITE block 482293536 on sda1
Nov 13 12:25:51 pcfreak kernel: [1075037.702824] kjournald(297): WRITE block 482293544 on sda1
Nov 13 12:25:52 pcfreak kernel: [1075039.219288] apache2(3377): dirtied inode 3571740 (_index.html.old) on sda1
Nov 13 12:25:52 pcfreak kernel: [1075039.436133] mysqld(22945): dirtied inode 21546676 (#sql_c0a_0.MYI) on sda1
Nov 13 12:25:52 pcfreak kernel: [1075039.436826] mysqld(22945): dirtied inode 21546677 (#sql_c0a_0.MYD) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075039.662832] mysqld(22945): dirtied inode 21546676 (#sql_c0a_0.MYI) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075039.663297] mysqld(22945): dirtied inode 21546677 (#sql_c0a_0.MYD) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075039.817120] apache2(3377): dirtied inode 3571754 (_index.html) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075039.819968] apache2(3377): dirtied inode 3571740 (_index.html_gzip) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075039.820016] apache2(3377): dirtied inode 3571730 (?) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075040.491378] mysqld(22931): dirtied inode 21546676 (#sql_c0a_0.MYI) on sda1
Nov 13 12:25:53 pcfreak kernel: [1075040.492309] mysqld(22931): dirtied inode 21546677 (#sql_c0a_0.MYD) on sda1
Nov 13 12:25:54 pcfreak kernel: [1075041.551513] apache2(3377): dirtied inode 1474706 (_index.html_gzip.old) on sda1
Nov 13 12:25:54 pcfreak kernel: [1075041.551566] apache2(3377): dirtied inode 1474712 (_index.html.old) on sda1
Nov 13 12:25:55 pcfreak kernel: [1075041.769036] mysqld(22941): dirtied inode 21546676 (#sql_c0a_0.MYI) on sda1
Nov 13 12:25:55 pcfreak kernel: [1075041.769804] mysqld(22941): dirtied inode 21546677 (#sql_c0a_0.MYD) on sda1
Nov 13 12:25:55 pcfreak kernel: [1075041.985857] apache2(3282): dirtied inode 4063282 (data_9d97a7f62d54bc5fd791fba3245ba591-SMF-modSettings.php) on sda1
Nov 13 12:25:55 pcfreak kernel: [1075041.987460] apache2(3282): dirtied inode 29010186 (data_9d97a7f62d54bc5fd791fba3245ba591-SMF-permissions–1.php) on sda1
Nov 13 12:25:55 pcfreak kernel: [1075041.988357] flush-8:0(289): WRITE block 51350632 on sda1

Using the kernel method to see which processes are stoning your server is great way especially for servers without connectivity to the Internet where you have no possibility to install sysstat package (contaning iostat),  dstat or glance.
Thanks to Marto's blog for  this nice hack.

Share this on

Enabling talkd (Console Chat) between logged in users on FreeBSD and other BSDs

Sunday, June 10th, 2012

Talk between two useres on  FreeBSD 7.2 screenshot, console peer to peer interactive talk program UNIX, Linux, BSD

Those who are in familiar with older UNIXes, UNIX BSD derivatives and GNU Linux should certainly remember the times, when we hackers used to talk to each other using talk service.

Those who don't know what talk command is it is a simple console / ssh utility to talk to another logged in users.

Talk is very similar to write and mesg one liner messasing utilities available for *nixes, the difference is it is intendted to provide interactive chat between the two logged in users. People who came to know UNIX or free software in older times most likely don't know talk, however I still remember how precious this tool was for communication back in the day.

I believe still it can be useful so I dediced to install ot on one FreeBSD host.

In order to have the talk service running on BSD it is necessery to have /usr/libexec/ntalkd installed on the system this however is installed by default with standard BSD OS installs, so no need for any external ports install to run it.

talk doesn't have it's own init script to start is not written to run as it own service but in order to run it is is necessery to enable it via inetd

Enabling it is done by;;;

1 — Editting /etc/inetd.conf

Inside the conf the line::

#ntalk dgram udp wait tty:tty /usr/libexec/ntalkd ntalkd

should be uncommented e.g, become ;;;

ntalk dgram udp wait tty:tty /usr/libexec/ntalkd ntalkd

2 — Restart inetd

freebsd# /etc/rc.d/inetd restart
Stopping inetd.
Starting inetd.

talk is planned to be used for peer to peer conversations over SSH so in a way it is the GRANDFATHER :) of IRC, ICQ and Skype;;;

Here is an example on how talk is used ,, Let's say there are three logged in users

pcfreak# w
12:39PM up 3 days, 16:25, 3 users, load averages: 1.12, 0.91, 0.71
USER TTY FROM LOGIN@ IDLE WHAT
testuser p0 192.168.0.7 10:50AM - bash
hipo p3 192.168.0.8 12:23PM - w
root p4 :ttyp2:S.0 12:24PM - vim /usr/local/www/dat

I'm logged in with my username hipo and I would like to talk to testuser ;;;;

pcfreak% tty
/dev/ttyp3

You see I'm logged in on /dev/ttyp3 (this is the specific naming on BSDs) on Linux equivalent is /dev/tty3So to talk the other user testuser;;;;;-

$ talk testuser ttyp0
[No connection yet]
[Waiting for your party to respond]

The testuser logged in via SSH will then get a message ||;

Message from Talk_Daemon@pcfreak at 12:44 on 2012/06/10 ...
talk: connection requested by hipo@localhost
talk: respond with: talk hipo@localhost

To enter a talk session then the logged in testuser has to type:

$ talk hipo@localhost

 

Share this on

Fix “Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.” in FreeBSD

Monday, May 21st, 2012

I'm running FreeBSD with Apache and PHP on it and I got in dmesg (kernel log), following error:

freebsd# dmesg|grep -i vm.pmap.shpgperproc
Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.
Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.
Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.
Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.
Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.

The exact FreeBSD, Apache and php versions I have installed are:
 

freebsd# uname -a ; httpd -V ; php –version
FreeBSD pcfreak 7.2-RELEASE-p4 FreeBSD 7.2-RELEASE-p4 #0: Fri Oct 2 12:21:39 UTC 2009 root@i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC i386
Server version: Apache/2.0.64
Server built: Mar 13 2011 23:36:25Server's Module Magic Number: 20050127:14
Server loaded: APR 0.9.19, APR-UTIL 0.9.19
Compiled using: APR 0.9.19, APR-UTIL 0.9.19
Architecture: 32-bit
Server compiled with….
-D APACHE_MPM_DIR="server/mpm/prefork"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_FLOCK_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D HTTPD_ROOT="/usr/local"
-D SUEXEC_BIN="/usr/local/bin/suexec"
-D DEFAULT_PIDLOG="/var/run/httpd.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_LOCKFILE="/var/run/accept.lock"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="etc/apache2/mime.types"
-D SERVER_CONFIG_FILE="etc/apache2/httpd.conf"
PHP 5.3.5 with Suhosin-Patch (cli) (built: Mar 14 2011 00:29:17)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
with eAccelerator v0.9.6.1, Copyright (c) 2004-2010 eAccelerator, by eAccelerator

After a bunch of research a FreeBSD forums thread , I've found the fix suggested by a guy.

The solution suggested in the forum is to raise up vm.pmap.pv_entry_ma to vm.pmap.pv_entry_max=1743504, however I've noticed this value is read only and cannot be changed on the BSD running kernel;

freebsd# sysctl vm.pmap.pv_entry_max=1743504
sysctl: oid 'vm.pmap.pv_entry_max' is read only

Instead to solve the;

Approaching the limit on PV entries, consider increasing either the vm.pmap.shpgperproc or the vm.pmap.pv_entry_max tunable.
, I had to add in /boot/loader.conf

vm.pmap.pde.mappings=68
vm.pmap.shpgperproc=500
vm.pmap.pv_entry_max=1743504

Adding this values through /boot/loader.conf set them on kernel boot time. I've seen also in the threads the consider increasing either the vm.pmap.shpgperproc is also encountered on FreeBSD hosts running Squid, Dansguardion and other web proxy softwares on busy hosts.

This problems are not likely to happen for people who are running latest FreeBSD releases (>8.3, 9.x), I've read in same above post in newer BSD kernels the vm.pmap is no longer existing in newer kernels.

Share this on

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
 

Share this on

How to convert html pages to text in console / terminal on GNU / Linux and FreeBSD

Thursday, December 8th, 2011

HTML to Plain Text Convertion on GNU / Linux and FreeBSD

I'm realizing the more I'm converting to a fully functional GUI user, the less I'm doing coding or any interesting stuff…
I remembered of the old glorious times, when I was full time console user and got a memory on a nifty trick I was so used to back in the day.
Back then I was quite often writing shell scripts which were fetching (html) webpages and converting the html content into a plain TEXT (TXT) files

In order to fetch a page back in the days I used lynx (a very simple UNIX text browser, which by the way lacks support for any CSS or Javascipt) in combination with html2text – (an advanced HTML-to-text converter).

Let's say I wanted to fetch a my personal home page http://www.pc-freak.net/, I did that via the command:

$ lynx -source http://www.pc-freak.net/ | html2text > pcfreak_page.txt

The content from www.pc-freak.net got spit by lynx as an html source and passed html2pdf wchich saves it in plain text file pcfreak_page.txt
The bit more advanced elinks – (lynx-like alternative character mode WWW browser) provides better support for HTML and even some CSS and Javascript so to properly save the content of many pages in plain html file its better to use it instead of lynx, the way to produce .txt using elinks files is identical, e.g.:

$ elinks -source http://www.pc-freak.net/blog/ | html2text > pcfreak_blog_page.txt

By the way back in the days I was used more to links , than the superior elinks , nowdays I have both of the text browsers installed and testing to fetch an html like in the upper example and pipe to html2text produced garbaged output.

Here is the time to tell its not even necessery to have a text browser installed in order to fetch a webpage and convert it to a plain text TXT!. wget file downloading tools supports source dump as well, for all those who did not (yet) tried it and want to test it:

$ wget -qO- http://www.pc-freak.net | html2text
Anyways of course, some pages convertion of text inside HTML tags would not properly get saved with neither lynx or elinks cause some texts might be embedded in some elinks or lynx unsupported CSS or JavaScript. In those cases the GUI browser is useful. You can use any browser like Firefox, Epiphany or Opera 's File -> Save As (Text Files) embedded functionality, below is a screenshot showing an html page which I'm about to save as a plain Text File in Mozilla Firefox:

Firefox iceWeasel Opera etc. save html webpage as plain text on GNU / Linux, FreeBSD

Besides being handy in conjunction with text browsers, html2text is also handy for converting .html pages already existing on the computer's hard drive to a plain (.TXT) text format.
One might wonder, why would ever one would like to do that?? Well I personally prefer reading plain text documents instead of htmls ;)
Converting an html files already existing on hard drive with html2text is done with cmd:

$ html2text index.html >index.txt

To convert a whole directory full of .html (documentation) or whatever files to plain text .TXT , cd the directory with HTMLs and issue the one liner bash loop command:

$ cd html/
html$ for i in $(echo *.html); do html2text $i > $(echo $i | sed -e 's#.html#.txt#g'); done

Now lay off your back and enjoy reading the dox like in the good old hacker days when .TXT files were fashionable ;)

Share this on

How to list enabled VirtualHosts in Apache on GNU / Linux and FreeBSD

Thursday, December 8th, 2011

How Apache process vhost requests picture, how to list Apache virtualhosts on Linux and FreeBSD

I decided to start this post with this picture I found on onlamp.com article called "Simplify Your Life with Apache VirtualHosts .I put it here because I thing it illustrates quite well Apache's webserver internal processes. The picture gives also a good clue when Virtual Hosts gets loaded, anways I'll go back to the main topic of this article, hoping the above picture gives some more insight on how Apache works.;
Here is how to list all the enabled virtualhosts in Apache on Debian GNU / Linux serving pages:

server:~# /usr/sbin/ apache2ctl -S
VirtualHost configuration:
wildcard NameVirtualHosts and _default_ servers:
*:* is a NameVirtualHost
default server exampleserver1.com (/etc/apache2/sites-enabled/000-default:2)
port * namevhost exampleserver2.com (/etc/apache2/sites-enabled/000-default
port * namevhost exampleserver3.com (/etc/apache2/sites-enabled/exampleserver3.com:1)
port * namevhost exampleserver4.com (/etc/apache2/sites-enabled/exampleserver4.com:1)
...
Syntax OK

The line *:* is a NameVirtualHost, means the Apache VirtualHosts module will be able to use Virtualhosts listening on any IP address (configured on the host), on any port configured for the respective Virtualhost to listen on.

The next output line:
port * namevhost exampleserver2.com (/etc/apache2/sites-enabled/000-default
Shows requests to the domain on any port will be accepted (port *) by the webserver as well as indicates the <VirtualHost> in the file /etc/apache2/sites-enabled/000-default:2 is defined on line 2 (e.g. :2).

To see the same all enabled VirtualHosts on FreeBSD the command to be issued is:

freebsd# pcfreak# /usr/local/sbin/httpd -S VirtualHost configuration:
wildcard NameVirtualHosts and _default_ servers:
*:80 is a NameVirtualHost
default server pc-freak.net (/usr/local/etc/apache2/httpd.conf:1218)
port 80 namevhost pc-freak.net (/usr/local/etc/apache2/httpd.conf:1218)
port 80 namevhost pcfreak.afraid.org (/usr/local/etc/apache2/httpd.conf:1353)
...
Syntax OK

On Fedora and the other Redhat Linux distributions, the apache2ctl -S should be displaying the enabled Virtualhosts.

One might wonder, what might be the reason for someone to want to check the VirtualHosts which are loaded by the Apache server, since this could be also checked if one reviews Apache / Apache2's config file. Well the main advantage is that checking directly into the file might sometimes take more time, especially if the file contains thousands of similar named virtual host domains. Another time using the -S option is better would be if some enabled VirtualHost in a config file seems to not be accessible. Checking directly if Apache has properly loaded the VirtualHost directives ensures, there is no problem with loading the VirtualHost. Another scenario is if there are multiple Apache config files / installs located on the system and you're unsure which one to check for the exact list of Virtual domains loaded.

Share this on

swap_pager_getswapspace: failed, MySQL troubles on FreeBSD 7.2 cause and solution

Tuesday, May 3rd, 2011

Every now and then my FreeBSD router dmesg ( /var/log/dmesg.today ) logs, gets filled with error messages like:

pid 86369 (httpd), uid 80, was killed: out of swap space
swap_pager_getswapspace(14): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(11): failed
swap_pager_getswapspace(12): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(14): failed
swap_pager_getswapspace(16): failed
swap_pager_getswapspace(8): failed

Using swapinfo during the swap_pager_getswapspace(16): failed messages were logged in, I figured out that definitely the swap memory over-use is the bottleneck for the troubles, to find this I used the command:

freebsd# swapinfo
Device 1K-blocks Used Avail Capacity Type
/dev/ad0s1b 49712 45920 3792 92% Interleaved

After some investigation, I've figured out that the MySQL server is causing the kernel exceeded swap troubles.

My current MySQL server version is installed from the ports tree, whether I'm using the bsd port /usr/ports/databases/mysql51-server/ and it appears to work just fine.

However I have noticed that the mysql-server is missing a my.cnf file!, which means the mysql server is running under a mode with some kind of default configurations.

Strangely in the system process list it appeared it is using a default my.cnf file located in /var/db/mysql/my.cnf

Below you see the paste from the ps command:

ps axuww freebsd# ps axuww | grep -i my.cnf | grep -v grep
mysql 7557 0.0 0.1 3464 1268 p1 I 12:03PM 0:00.01 /bin/sh /usr/local/bin/mysqld_safe --defaults-extra-file=/var/db/mysql/my.cnf --user=mysql --datadir=/var/db/mysql --pid-file=/var/db/mysql/pcfreak.pidmysql 7589 0.0 5.1 93284 52852 p1 I 12:03PM 0:59.01 /usr/local/libexec/mysqld --defaults-extra-file=/var/db/mysql/my.cnf --basedir=/usr/local --datadir=/var/db/mysql --user=mysql --pid-file=/var/db/mysql/pcfreak.pid --port=3306 --socket=/tmp/mysql.sock

Nevertheless it appeared the sql server is running the file /var/db/mysql/my.cnf conf was not existing! This was really weird for me as I'm used to have the default my.cnf from my previous experience with Linux servers!

Thus the next logical thing I did was to create my.cnf conf file in order to be able to have a proper limiting configuration for the sql server.

The FreeBSD my.cnf skele files are found in /usr/local/share/mysql/, here are the 4 files one can use as a starting basis for further configuration of the mysql-server.

freebsd# ls -al /usr/local/share/mysql/my-*.cnf
-r--r--r-- 1 root wheel 4948 Aug 12 2009 /usr/local/share/mysql/my-huge.cnf
-r--r--r-- 1 root wheel 20949 Aug 12 2009 /usr/local/share/mysql/my-innodb-heavy-4G.cnf
-r--r--r-- 1 root wheel 4924 Aug 12 2009 /usr/local/share/mysql/my-large.cnf
-r--r--r-- 1 root wheel 4931 Aug 12 2009 /usr/local/share/mysql/my-medium.cnf
-r--r--r-- 1 root wheel 2502 Aug 12 2009 /usr/local/share/mysql/my-small.cnf

I have chosen to use the my-medium.cnf as a skele to tune up, as my server is not high iron one e.g. the host I run the mysql is a (simple dual core 1.2Ghz system).

Further on I copied the /usr/local/share/mysql/my-medium.cnf to /var/db/mysql/my.cnf e.g.:

freebsd# cp -rpf /usr/local/share/mysql/my-medium.cnf /var/db/mysql/my.cnf

As a next step to properly tune up the default values of the newly copied my.cnf to my specific server I used the Tuning-Primer MySQL tuning script

Using tuning-primer.sh is really easy as all I did is download, launch it and follow the script suggestions to correct some of the values already in my.cnf

I have finally ended up with the following my.cnf after using tuning-primer.sh to optimize mysql server to work with my bsd host

Now I really hope the shitty swap_pager_getswapspace: failed errors would not haunt me once again by crashing my server and causing mem overheads.

Still I wonder why the port developer Alex Dupre – ale@FreeBSD.org choose not to provide the default mysql51-server conf with some kind of my.cnf file? I hope he had a good reason.

Share this on