Ubuntu desktop vs server kernel

http://www.enterprisenetworkingplanet.com/netos/article.php/10951_3710641_2
http://www.enterprisenetworkingplanet.com/img/examples/ubuntu_server_config_diff.html
http://www.enterprisenetworkingplanet.com/netos/article.php/3709221
http://lists.netisland.net/archives/plug/plug-2008-06/msg00189.html

ntpq

ntpq -p

to display the status of the daemon on the local machine, or

ntpq -p ntp_server

to display the status of the daemon on the remote host ntp_server. The command should print a table with one status line for each reference time source which has been configured for the NTP daemon on the specified host:

   remote      refid      st t when poll reach   delay   offset  jitter
=======================================================================
 LOCAL(0)      LOCAL(0)   12 l   30   64  377    0.000    0.000   0.000
*GENERIC(0)    .DCFa.      0 -   24   64  377    0.000    0.050   0.003
+172.16.3.103  .PPS.       1 u   36   64  377    1.306   -0.019   0.043

The table above shows the output for a NTP daemon which has 3 reference time sources: its own local clock, a DCF77 radio clock as refclock-0, plus an NTP daemon on the network, with IP address 172.16.3.103.

If the first character of a line is not blank then it contains a qualifier for the corresponding reference time source. Immediately after the daemon has been started all qualifiers are blank. The NTP daemon needs several polling cycles to check the available time sources and declare one of them as the reference it synchronizes to.

An asterisk * in the first column marks the reference time source which is currently preferred by the NTP daemon, the + character marks high quality candidates for the reference time which could be used if the currently selected reference time source should become unavailable.

The column remote displays the IP address or the host name of the reference time source, where LOCAL refers to the local clock. The refid shows the type of the reference clock, where e.g. LOCAL or LCL refers to the local clockagain, .DCFa. refers to a standard DCF77 time source, and .PPS. indicates that the reference clock is disciplined by a hardware pulse-per-second signal. Other identifiers are possible, depending on the type of the reference clock.

The column st reflects the stratum number of the reference time source. In the example above, the local clock has stratum 12, the remote time server at 172.16.3.103 has stratum 1 which is the best you can see across the network, and the local radio clock has stratum 0, so the radio clock is currently being preferred.

Every time a when count reaches the poll number in the same line, the NTP daemon queries the time from the corresponding time source and resets the when count to 0. The query results of each polling cycle are filtered and used as a measure for the clock's quality and reachability.

The column reach shows if a reference time source could be reached at the last polling intervals, i.e. data could be read from the reference time source, and the reference time source was synchronized. The value must be interpreted as an 8 bit shift register whose contents is displayed as octal values. If the NTP daemon has just started, the value is 0. Each time a query was successful a '1' is shifted in from the right, so after the daemon has been started the sequence of reach numbers 0, 1, 3, 7, 17, 37, 77, 177, 377. The maximum value 377 means that the eight last queries were completed successfully. The NTP daemon must have reached a reference time source several times (reach not 0) before it selects a preferred time source and puts an asterisk in the first column.

The columns delay, offset and jitter show some timing values which are derived from the query results. In some versions of ntpq the last column is labeled disp (for dispersion) instead of jitter. All values are in in milliseconds. The delay value is derived from the roundtrip time of the queries. The offset value shows the difference between the reference time and the system clock. The jitter value indicates the magnitude of jitter between several time queries.

REPLACE vs. INSERT ... ON DUPLICATE UPDATE in MySQL

REPLACE works exactly like INSERT, except that if an old row in the table has the same value as a new row for a PRIMARY KEY or a UNIQUE index, the old row is deleted before the new row is inserted.

REPLACE is a MySQL extension to the SQL standard. It either inserts, or deletes and inserts.

For another MySQL extension to standard SQL — that either inserts or updates — it should be use “INSERT ... ON DUPLICATE KEY UPDATE Syntax”.

If you specify ON DUPLICATE KEY UPDATE, and a row is inserted that would cause a duplicate value in a UNIQUE index or PRIMARY KEY, an UPDATE of the old row is performed.

REPLACE (http://dev.mysql.com/doc/refman/5.1/en/replace.html)

INSERT ... ON DUPLICATE UPDATE (http://dev.mysql.com/doc/refman/5.1/en/insert-on-duplicate.html)

Recover MySQL Database root password

If you have set the password for root and forget or unable to recall the password, then you will need to reset the root password for MySQL.

Login as root to the Unix-like (Unix, Linux or BSD) machine with the MySQL server.

Stop the MySQL server by using either of the following command

#/etc/init.d/mysql stop

Now you need to Start MySQL server without password

# mysqld_safe --skip-grant-tables &

Connect to mysql server using mysql client with the following command

# mysql -u root

Now you should be having mysql prompt

mysql>

Now you need to Setup new MySQL root user password

mysql> use mysql;

mysql> update user set password=PASSWORD(”newrootpassword”) where user=’root’;

mysql> flush privileges;

mysql> quit

Note: Replace newrootpassword with the new root password for MySQL server. Flush Privileges is needed to making the password change effect immediately.

Now you need to Stop MySQL Server using the following command

# /etc/init.d/mysql stop

Test Your New Mysql root password

First you need to start mysql server using the following command

# /etc/init.d/mysql start

# mysql -u root -p

Now it will prompt for root password and enter your new root password.

Taken from: http://www.debianadmin.com/recover-mysql-database-root-password.html

Ubuntu version

lsb_release -a

No LSB modules are available.

Distributor ID: Ubuntu

Description: Ubuntu 9.04

Release: 9.04

Codename: jaunty

Sed Links

• IBM Developer Works Common Threads: Sed by Example:
  • Part 1<http://www-106.ibm.com/developerworks/linux/library/l-sed1.html>
  • Part 2<http://www-106.ibm.com/developerworks/linux/library/l-sed2.html>
  • Part 3<http://www-106.ibm.com/developerworks/linux/library/l-sed3.html>
• Sed FAQ<http://sed.sourceforge.net/sedfaq.html>
• Grymoire Sed Tutorial<http://www.grymoire.com/Unix/Sed.html>
• Sed and Regular Expressions<http://main.rtfiber.com.tw/~changyj/sed>
• Sourceforge project Sed<http://sed.sourceforge.net>
• SedSed<http://sedsed.sourceforge.net>
• Sed specification<http://www.opengroup.org/onlinepubs/009695399/utilities/sed.html>
• Regular expressions specification<http://www.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap09.html>
• Sed Tutorial<http://www.panix.com/~elflord/unix/sed.html>
• Sed Users Mailing List<http://groups.yahoo.com/group/sed-users>

Playing with DATE and FOR in XP DOS

@echo off

rem for /F "tokens=1-4 delims=/ " %%i in ('date /t') do set dow=%%i && set month=%%j && set day=%%k && set year=%%l

rem for /F "tokens=1-4 delims=/ " %%i in ('date /t') do set dow=%%i && set date=%%j-%%k-%%l

rem for /F "tokens=2-4 delims=/ " %%i in ('date /t') do set date=%%i-%%j-%%k

for /F "tokens=1-4 delims=/ " %%i in ("%DATE%") do (

set dow=%%i

set dom=%%j-%%k-%%l

set month=%%j

set day=%%k

set year=%%l

)

set datew=%DATE:~0,3%

set datem=%DATE:~4,2%-%DATE:~7,2%-%DATE:~10,4%

set daten=%month%.%day%.%year%

echo %dow%

echo %datew%

echo %datem%

echo %daten%

Configure TIMEZONE in Ubuntu 9.04, the current stable version, released in April 2009, codenamed Jaunty Jackalope

dpkg-reconfigure tzdata

tzconfig command is deprecated.

UDP server in Perl

#!/usr/bin/perl

use strict;

use warnings;

use IO::Socket::INET;

use IO::Handle;

if ($#ARGV <>

die "Argument should be an integer port number\n";

} elsif ($ARGV[0] =~ /\D+/) {

die "Argument should be an integer port number\n";

}

my $Port = $ARGV[0];

my $MySocket = new IO::Socket::INET->new(

LocalPort => $Port,

Proto => 'udp'

) or die "Error opening UDP port $Port $!\n";

print "\nListening on UDP port $Port ...\n\n";

my $MsgText;

open(FILE, ">>udpserver.txt") or die "Error opening udpserver.txt file $!\n";

FILE->autoflush(1);

$MySocket->autoflush();

my $count = 1;

while ($MySocket->recv($MsgText, 4096)) {

print "$count <$MsgText>\n";

print FILE "$count <$MsgText>\n";

$count++;

}

close(FILE);

__END__

AnkhSVN

Subversion for Visual Studio

AnkhSVN is a Subversion SourceControl Provider for Visual Studio. The software allows you to perform the most common version control operations directly from inside the Microsoft Visual Studio IDE. With AnkhSVN you no longer need to leave your IDE to perform tasks like viewing the status of your source code, updating your Subversion working copy and committing changes. You can even browse your repository and you can plug-in your favorite diff tool.

AnkhSVN is an active open source project with multiple committers from around the world (including CollabNet).

The site is: http://ankhsvn.open.collab.net/

The Thread Control Escape Rule

When trying to determine if your code's access of a certain resource is thread safe you can use the thread control escape rule:

If a resource is created, used and disposed within
the control of the same thread,
and never escapes the control of this thread,
the use of that resource is thread safe.

Resources can be any shared resource like an object, array, file, database connection, socket etc. In Java you do not always explicitly dispose objects, so "disposed" means losing or null'ing the reference to the object.

Taken from: http://tutorials.jenkov.com/java-concurrency/thread-safety.html

bootadm

bootadm– manage bootability of GRUB-enabled operating system

The bootadm command manages the boot archive and, with x86 boot environments, the GRUB (GRand Unified Bootloader) menu.

The set-menu subcommand allows you to switch the auto-boot timeout and default boot entry in the GRUB menu.

The list-menu subcommand displays the location of the GRUB menu and the current GRUB menu entries. While the typical location of the GRUB menu is /boot/grub/menu.lst, depending on the install method used the active GRUB menu might be located somewhere else. Use the list-menu subcommand to locate the active GRUB menu. For example, if a system was installed using Live Upgrade, the GRUB menu might not be located in the current boot environment. See the EXAMPLES section for typical output from the list-menu option.

Note that OpenBoot PROM (OBP)-based machines, such as SPARC systems, do not use GRUB and have no boot menu manageable by bootadm.

The bootadm command has the following subcommands:

set-menu

Maintain the GRUB menu. The current GRUB menu is boot/grub/menu.lst, relative to root. Do not depend on this location, because it is subject to change. Applies to x86 platforms only.

list-menu

Lists the location of the active GRUB menu, as well as the current GRUB menu entries. This includes the autoboot-timeout, the default entry number, and the title of each entry. Applies to x86 platforms only.

key=value

Possible values are:

default=entrynum

The item number (for example, 0, 1, or 2) in the GRUB menu designating the operating system to boot when the timer expires.

timeout=seconds

The number of seconds before the operating system designated by the default item number is booted. If the value is –1, auto boot is disabled.

Examples

Example 1 Updating the Current Boot Archive

The following command lists the installed operating system instances in a GRUB menu:

# bootadm list-menu

default=0

timeout=10

(0) Solaris10

(1) Solaris10 Failsafe

(2) Linux

Example 2 Switching Default Boot Entry

The following command refers to the menu displayed in the previous example. The user selects Linux (item 2).

# bootadm set-menu default=2