Posted inc linux programing

Zombie Process

A zombie, or defunct, process is a process that has terminated, but its parent process has not taken it out of the process table with the wait() family of system calls. This typically happens when a program forks/execs another program, but then doesn’t reap it properly. The easiest way to write the parent to properly reap its children is to setup a signal handler for SIGCHLD that calls wait().

See the man pages on your local system for signal and wait(2).

Zombie and defunct states of a process are different things. Zombie is created when a child dies and parent didn’t call wait. Defunct is created when parent dies before the child finishes.

Defunct processes can’t be killed since they are already dead. To make them disappear you have to kill their parent process…

It’s not possible to kill defunct processes.

A good way to kill lists of processes is:

$ ps axf | grep name-of-process | grep -v -grep | awk '{print "kill -9 ",$1}' | sh
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Posted inlinux

Found 20 files with the largest size

e.g. [bash] # find /var/log -type f -exec du -sm {} \; | sort -n -r | head -20 [/bash] [bash] 41 /var/log/cabal/WorldSvr_10_01.log 35 /var/log/cabal/DBAgent_10.log 34 /var/log/cabal/WorldSvr_10_10.log 5 /var/log/maillog.4 5 /var/log/maillog.3 5 /var/log/cabal/WorldSvr_10_05.log 5 /var/log/cabal/WorldSvr_10_04.log 5 /var/log/cabal/WorldSvr_10_02.log 4 /var/log/cabal/WorldSvr_10_03.log 4 /var/log/cabal/LoginSvr_01.log 3 /var/log/maillog.2 3 /var/log/maillog.1 1 /var/log/yum.log 1 /var/log/Xorg.0.log.old 1…
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Posted inlinux

Colouring MOTD

Terminal should be ANSI compliant and support colour escape sequences. Modern terminal should do the job.

The following is a list of escape sequences

The ^[ is produced by pressing Ctrl-V then ESC

I’m using vi as text editor and there’s no problem with ctrl-V ESC, i’m not test it on other text editor.

^[[0m    - Reset the terminal characteristics
^[[1m    - emphasis (bold)

^[[30m    - Foreground black
^[[31m    - Foreground red
^[[32m    - Foreground green
^[[33m    - Foreground yellow
^[[34m    - Foreground blue
^[[35m    - Foreground magenta
^[[36m    - Foreground cyan
^[[37m    - Foreground white
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Posted inlinux php

Speeding up your website using eaccelerator and memcache/memcached

Php default behaviour is always re-compile our script everytime accessed by users/browsers. eaccelerator can increases the performance of PHP scripts by caching them in their compiled state, so that the overhead of compiling is almost completely eliminated. It also optimizes scripts to speed up their execution. eAccelerator typically reduces server load and increases the speed of your PHP code by 1-10 times.

memcached is a high-performance, distributed memory object caching system, generic in nature, but intended for use in speeding up dynamic web applications by alleviating database load.

Here’s how to install eaccelerator extension

$ wget http://bart.eaccelerator.net/source/0.9.6/eaccelerator-0.9.6-rc1.tar.bz2
$ tar xjf eaccelerator-0.9.6-rc1.tar.bz2
$ cd eaccelerator-0.9.6-rc1
$ phpize
$ ./configure
$ make
$ sudo make install
$ cd /var/cache
$ sudo mkdir eaccelerator
$ sudo chown -R apache:apache eaccelerator
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Posted inlinux

How to calculate linux user umask

Suppose we have umask 0002 for our user default permission. [bash] $ umask 0002 [/bash] Create new directory [bash] $ mkdir tmpdir [/bash] tmpdir directory created with its default permission 775 [bash] $ ls -l .......... .......... drwxrwxr-x 2 harry harry 4096 Oct 8 06:59 tmp .......... .......... [/bash] Create…
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Posted inlinux vim

Using VIM as stream editor

Every person associated with the unix / linux would be familiar with the text editor called vi / vim. but not many people know that vi / vim can be used as a stream editor. This is one example of how to use vi / vim as a text editor.…
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Posted infilesystem linux

mounting remote filesystem via nfs

Step 1: Start nfs, nfslock, portmap services [bash] remote-server# service portmap start remote-server# service nfs start remote-server# service nfslock start [/bash] Step 2: On remote server destination edit file /etc/exports For example we will mounting /var/data/ directory on remote server [text] /var/data local-ip(rw,sync,no_wdelay,no_subtree_check,all_squash,anonuid=89,anongid=89) [/text] anonuid and anongid These options explicitly…
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Posted inlinux vlan

VLANs on Linux

VLANs on Linux

An introduction to VLANs and VLAN trunking, how Linux interacts with VLANs and how you might use them in networks.
To begin, we must have a more formal definition of what a LAN is. LAN stands for local area network. Hubs and switches usually are thought of as participating in a single LAN. Normally, if you connect two computers to the same hub or switch, they are on the same LAN. Likewise, if you connect two switches together, they are both on the same LAN.
A LAN includes all systems in the broadcast domain. That is, all of the systems on a single LAN receive a broadcast sent by any member of that LAN. By this definition, a LAN is bordered by routers or other devices that operate at OSI Layer 3.
Now that we’ve defined a LAN, what is a VLAN? VLAN stands for virtual LAN. A single VLAN-capable switch is able to participate in multiple LANs at once.
This functionality alone has a variety of uses, but VLANs become far more interesting when combined with trunking. A trunk is a single physical connection that can carry multiple VLANs. Each frame that crosses the trunk has a VLAN identifier attached to it, so it can be identified and kept within the correct VLAN.
Trunks can be used between two switches, between a switch and a router or between a switch and a computer that supports trunking. When connecting to a router or computer, each VLAN appears as a separate virtual interface.

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Posted inip linux

How to Configure Your NIC’s IP Address

You need to know all the steps needed to configure IP addresses on a NIC card. Web site shopping cart applications frequently need an additional IP address dedicated to them. You also might need to add a secondary NIC interface to your server to handle data backups. Last but not least, you might just want to play around with the server to test your skills.

This section shows you how to do the most common server IP activities with the least amount of headaches.

Determining Your IP Address

Most modern PCs come with an Ethernet port. When Linux is installed, this device is called eth0. You can determine the IP address of this device with the ifconfig command.

[root@bigboy tmp]# ifconfig -a

eth0 Link encap:Ethernet HWaddr 00:08:C7:10:74:A8
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
Interrupt:11 Base address:0x1820

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:787 errors:0 dropped:0 overruns:0 frame:0
TX packets:787 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:82644 (80.7 Kb) TX bytes:82644 (80.7 Kb)

wlan0 Link encap:Ethernet HWaddr 00:06:25:09:6A:B5
inet addr:192.168.1.100 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:47379 errors:0 dropped:0 overruns:0 frame:0
TX packets:107900 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:4676853 (4.4 Mb) TX bytes:43209032 (41.2 Mb)
Interrupt:11 Memory:c887a000-c887b000

wlan0:0 Link encap:Ethernet HWaddr 00:06:25:09:6A:B5
inet addr:192.168.1.99 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:11 Memory:c887a000-c887b000

[root@bigboy tmp]#
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