Archive for category Red hat Linux tips

Linux Important System Files

File Purpose Where to Find More Information
User and Security Files
/etc/group User group information group, chmod
/etc/npasswd npasswd configuration file npasswd
/etc/shadow shadow password file password, npasswd
/etc/passwd User account information password, chmod
Networking Files
/etc/bootptab Internet Bootstrap Protocol server database bootptab
/etc/exports Directories to export to NFS clients exports
/etc/gateways List of gateways routed
/etc/hosts Hostname to IP address mapping file route
/etc/hosts.equiv Lists of trusted hosts and remote users hosts.equiv
/etc/inetd.conf inetd configuration file inetd
/etc/named.conf named default initialization file named
/etc/networks Known networks route
/usr/lib/named or/etc/named.d named configuration files named
/etc/smb.conf or /etc/samba/smb.conf SAMBA configuration file smb.conf
/etc/snmpd.conf SNMP daemon configuration file snmpd.conf
/etc/ftpaccess FTP configuration file ftpaccess
/etc/httpd/access.conf HTTP access configuration file
/etc/httpd/httpd.conf HTTP daemon configuration file
/etc/httpd/srm.conf HTTP server resource management configuration file
/etc/services Network services list services(5)
X-Windows Files
/etc/XF86Config or /etc/X11/XF86Config X-Server configuration file XF86Config, xf86config
/etc/X11/xinit/xinitrc xinit configuration file xinit
$HOME/.xinitrc User-specific xinit configuration file xinit
$HOME/.fvwmrc fvwm configuration file fvwm, X
/usr/lib/X11/system.fvwmrc System default MWM configuration file fvwm, X
/usr/lib/X11/app-defaults Application-specific defaults X
$HOME/.Xdefaults-hostname Host-specific defaults X
System Start-Up Files
/etc/inittab init configuration file inittab
/etc/lilo.conf Lilo configuration file lilo.conf, lilo
/etc/rc* System start-up scripts init, initscript
System Log Files
/etc/syslog.conf System login configuration file syslog.conf
/var/log/message General system log file syslogd
Miscellaneous Files
/etc/profile
/etc/bashrc
/etc/cshrc
Systemwide shell configuration files man-page for respective shell
$HOME/.bashrc
$HOME/.chsrc
$HOME/.kshrc
User-specifc shell configuration files man-page for respective shell
/etc/sysconfig Miscellaneous configuration files

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configure Kdump in centos (to recover data)

1	================================================================
2	Documentation for Kdump - The kexec-based Crash Dumping Solution
3	================================================================
4	
5	This document includes overview, setup and installation, and analysis
6	information.
7	
8	Overview
9	========
10	
11	Kdump uses kexec to quickly boot to a dump-capture kernel whenever a
12	dump of the system kernel's memory needs to be taken (for example, when
13	the system panics). The system kernel's memory image is preserved across
14	the reboot and is accessible to the dump-capture kernel.
15	
16	You can use common commands, such as cp and scp, to copy the
17	memory image to a dump file on the local disk, or across the network to
18	a remote system.
19	
20	Kdump and kexec are currently supported on the x86, x86_64, ppc64, ia64,
21	and s390x architectures.
22	
23	When the system kernel boots, it reserves a small section of memory for
24	the dump-capture kernel. This ensures that ongoing Direct Memory Access
25	(DMA) from the system kernel does not corrupt the dump-capture kernel.
26	The kexec -p command loads the dump-capture kernel into this reserved
27	memory.
28	
29	On x86 machines, the first 640 KB of physical memory is needed to boot,
30	regardless of where the kernel loads. Therefore, kexec backs up this
31	region just before rebooting into the dump-capture kernel.
32	
33	Similarly on PPC64 machines first 32KB of physical memory is needed for
34	booting regardless of where the kernel is loaded and to support 64K page
35	size kexec backs up the first 64KB memory.
36	
37	For s390x, when kdump is triggered, the crashkernel region is exchanged
38	with the region [0, crashkernel region size] and then the kdump kernel
39	runs in [0, crashkernel region size]. Therefore no relocatable kernel is
40	needed for s390x.
41	
42	All of the necessary information about the system kernel's core image is
43	encoded in the ELF format, and stored in a reserved area of memory
44	before a crash. The physical address of the start of the ELF header is
45	passed to the dump-capture kernel through the elfcorehdr= boot
46	parameter. Optionally the size of the ELF header can also be passed
47	when using the elfcorehdr=[size[KMG]@]offset[KMG] syntax.
48	
49	
50	With the dump-capture kernel, you can access the memory image, or "old
51	memory," in two ways:
52	
53	- Through a /dev/oldmem device interface. A capture utility can read the
54	  device file and write out the memory in raw format. This is a raw dump
55	  of memory. Analysis and capture tools must be intelligent enough to
56	  determine where to look for the right information.
57	
58	- Through /proc/vmcore. This exports the dump as an ELF-format file that
59	  you can write out using file copy commands such as cp or scp. Further,
60	  you can use analysis tools such as the GNU Debugger (GDB) and the Crash
61	  tool to debug the dump file. This method ensures that the dump pages are
62	  correctly ordered.
63	
64	
65	Setup and Installation
66	======================
67	
68	Install kexec-tools
69	-------------------
70	
71	1) Login as the root user.
72	
73	2) Download the kexec-tools user-space package from the following URL:
74	
75	http://kernel.org/pub/linux/utils/kernel/kexec/kexec-tools.tar.gz
76	
77	This is a symlink to the latest version.
78	
79	The latest kexec-tools git tree is available at:
80	
81	git://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
82	and
83	http://www.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
84	
85	There is also a gitweb interface available at
86	http://www.kernel.org/git/?p=utils/kernel/kexec/kexec-tools.git
87	
88	More information about kexec-tools can be found at
89	http://www.kernel.org/pub/linux/utils/kernel/kexec/README.html
90	
91	3) Unpack the tarball with the tar command, as follows:
92	
93	   tar xvpzf kexec-tools.tar.gz
94	
95	4) Change to the kexec-tools directory, as follows:
96	
97	   cd kexec-tools-VERSION
98	
99	5) Configure the package, as follows:
100	
101	   ./configure
102	
103	6) Compile the package, as follows:
104	
105	   make
106	
107	7) Install the package, as follows:
108	
109	   make install
110	
111	
112	Build the system and dump-capture kernels
113	-----------------------------------------
114	There are two possible methods of using Kdump.
115	
116	1) Build a separate custom dump-capture kernel for capturing the
117	   kernel core dump.
118	
119	2) Or use the system kernel binary itself as dump-capture kernel and there is
120	   no need to build a separate dump-capture kernel. This is possible
121	   only with the architectures which support a relocatable kernel. As
122	   of today, i386, x86_64, ppc64 and ia64 architectures support relocatable
123	   kernel.
124	
125	Building a relocatable kernel is advantageous from the point of view that
126	one does not have to build a second kernel for capturing the dump. But
127	at the same time one might want to build a custom dump capture kernel
128	suitable to his needs.
129	
130	Following are the configuration setting required for system and
131	dump-capture kernels for enabling kdump support.
132	
133	System kernel config options
134	----------------------------
135	
136	1) Enable "kexec system call" in "Processor type and features."
137	
138	   CONFIG_KEXEC=y
139	
140	2) Enable "sysfs file system support" in "Filesystem" -> "Pseudo
141	   filesystems." This is usually enabled by default.
142	
143	   CONFIG_SYSFS=y
144	
145	   Note that "sysfs file system support" might not appear in the "Pseudo
146	   filesystems" menu if "Configure standard kernel features (for small
147	   systems)" is not enabled in "General Setup." In this case, check the
148	   .config file itself to ensure that sysfs is turned on, as follows:
149	
150	   grep 'CONFIG_SYSFS' .config
151	
152	3) Enable "Compile the kernel with debug info" in "Kernel hacking."
153	
154	   CONFIG_DEBUG_INFO=Y
155	
156	   This causes the kernel to be built with debug symbols. The dump
157	   analysis tools require a vmlinux with debug symbols in order to read
158	   and analyze a dump file.
159	
160	Dump-capture kernel config options (Arch Independent)
161	-----------------------------------------------------
162	
163	1) Enable "kernel crash dumps" support under "Processor type and
164	   features":
165	
166	   CONFIG_CRASH_DUMP=y
167	
168	2) Enable "/proc/vmcore support" under "Filesystems" -> "Pseudo filesystems".
169	
170	   CONFIG_PROC_VMCORE=y
171	   (CONFIG_PROC_VMCORE is set by default when CONFIG_CRASH_DUMP is selected.)
172	
173	Dump-capture kernel config options (Arch Dependent, i386 and x86_64)
174	--------------------------------------------------------------------
175	
176	1) On i386, enable high memory support under "Processor type and
177	   features":
178	
179	   CONFIG_HIGHMEM64G=y
180	   or
181	   CONFIG_HIGHMEM4G
182	
183	2) On i386 and x86_64, disable symmetric multi-processing support
184	   under "Processor type and features":
185	
186	   CONFIG_SMP=n
187	
188	   (If CONFIG_SMP=y, then specify maxcpus=1 on the kernel command line
189	   when loading the dump-capture kernel, see section "Load the Dump-capture
190	   Kernel".)
191	
192	3) If one wants to build and use a relocatable kernel,
193	   Enable "Build a relocatable kernel" support under "Processor type and
194	   features"
195	
196	   CONFIG_RELOCATABLE=y
197	
198	4) Use a suitable value for "Physical address where the kernel is
199	   loaded" (under "Processor type and features"). This only appears when
200	   "kernel crash dumps" is enabled. A suitable value depends upon
201	   whether kernel is relocatable or not.
202	
203	   If you are using a relocatable kernel use CONFIG_PHYSICAL_START=0x100000
204	   This will compile the kernel for physical address 1MB, but given the fact
205	   kernel is relocatable, it can be run from any physical address hence
206	   kexec boot loader will load it in memory region reserved for dump-capture
207	   kernel.
208	
209	   Otherwise it should be the start of memory region reserved for
210	   second kernel using boot parameter "crashkernel=Y@X". Here X is
211	   start of memory region reserved for dump-capture kernel.
212	   Generally X is 16MB (0x1000000). So you can set
213	   CONFIG_PHYSICAL_START=0x1000000
214	
215	5) Make and install the kernel and its modules. DO NOT add this kernel
216	   to the boot loader configuration files.
217	
218	Dump-capture kernel config options (Arch Dependent, ppc64)
219	----------------------------------------------------------
220	
221	1) Enable "Build a kdump crash kernel" support under "Kernel" options:
222	
223	   CONFIG_CRASH_DUMP=y
224	
225	2)   Enable "Build a relocatable kernel" support
226	
227	   CONFIG_RELOCATABLE=y
228	
229	   Make and install the kernel and its modules.
230	
231	Dump-capture kernel config options (Arch Dependent, ia64)
232	----------------------------------------------------------
233	
234	- No specific options are required to create a dump-capture kernel
235	  for ia64, other than those specified in the arch independent section
236	  above. This means that it is possible to use the system kernel
237	  as a dump-capture kernel if desired.
238	
239	  The crashkernel region can be automatically placed by the system
240	  kernel at run time. This is done by specifying the base address as 0,
241	  or omitting it all together.
242	
243	  crashkernel=256M@0
244	  or
245	  crashkernel=256M
246	
247	  If the start address is specified, note that the start address of the
248	  kernel will be aligned to 64Mb, so if the start address is not then
249	  any space below the alignment point will be wasted.
250	
251	
252	Extended crashkernel syntax
253	===========================
254	
255	While the "crashkernel=size[@offset]" syntax is sufficient for most
256	configurations, sometimes it's handy to have the reserved memory dependent
257	on the value of System RAM -- that's mostly for distributors that pre-setup
258	the kernel command line to avoid a unbootable system after some memory has
259	been removed from the machine.
260	
261	The syntax is:
262	
263	    crashkernel=<range1>:<size1>[,<range2>:<size2>,...][@offset]
264	    range=start-[end]
265	
266	    'start' is inclusive and 'end' is exclusive.
267	
268	For example:
269	
270	    crashkernel=512M-2G:64M,2G-:128M
271	
272	This would mean:
273	
274	    1) if the RAM is smaller than 512M, then don't reserve anything
275	       (this is the "rescue" case)
276	    2) if the RAM size is between 512M and 2G (exclusive), then reserve 64M
277	    3) if the RAM size is larger than 2G, then reserve 128M
278	
279	
280	
281	Boot into System Kernel
282	=======================
283	
284	1) Update the boot loader (such as grub, yaboot, or lilo) configuration
285	   files as necessary.
286	
287	2) Boot the system kernel with the boot parameter "crashkernel=Y@X",
288	   where Y specifies how much memory to reserve for the dump-capture kernel
289	   and X specifies the beginning of this reserved memory. For example,
290	   "crashkernel=64M@16M" tells the system kernel to reserve 64 MB of memory
291	   starting at physical address 0x01000000 (16MB) for the dump-capture kernel.
292	
293	   On x86 and x86_64, use "crashkernel=64M@16M".
294	
295	   On ppc64, use "crashkernel=128M@32M".
296	
297	   On ia64, 256M@256M is a generous value that typically works.
298	   The region may be automatically placed on ia64, see the
299	   dump-capture kernel config option notes above.
300	
301	   On s390x, typically use "crashkernel=xxM". The value of xx is dependent
302	   on the memory consumption of the kdump system. In general this is not
303	   dependent on the memory size of the production system.
304	
305	Load the Dump-capture Kernel
306	============================
307	
308	After booting to the system kernel, dump-capture kernel needs to be
309	loaded.
310	
311	Based on the architecture and type of image (relocatable or not), one
312	can choose to load the uncompressed vmlinux or compressed bzImage/vmlinuz
313	of dump-capture kernel. Following is the summary.
314	
315	For i386 and x86_64:
316		- Use vmlinux if kernel is not relocatable.
317		- Use bzImage/vmlinuz if kernel is relocatable.
318	For ppc64:
319		- Use vmlinux
320	For ia64:
321		- Use vmlinux or vmlinuz.gz
322	For s390x:
323		- Use image or bzImage
324	
325	
326	If you are using a uncompressed vmlinux image then use following command
327	to load dump-capture kernel.
328	
329	   kexec -p <dump-capture-kernel-vmlinux-image> \
330	   --initrd=<initrd-for-dump-capture-kernel> --args-linux \
331	   --append="root=<root-dev> <arch-specific-options>"
332	
333	If you are using a compressed bzImage/vmlinuz, then use following command
334	to load dump-capture kernel.
335	
336	   kexec -p <dump-capture-kernel-bzImage> \
337	   --initrd=<initrd-for-dump-capture-kernel> \
338	   --append="root=<root-dev> <arch-specific-options>"
339	
340	Please note, that --args-linux does not need to be specified for ia64.
341	It is planned to make this a no-op on that architecture, but for now
342	it should be omitted
343	
344	Following are the arch specific command line options to be used while
345	loading dump-capture kernel.
346	
347	For i386, x86_64 and ia64:
348		"1 irqpoll maxcpus=1 reset_devices"
349	
350	For ppc64:
351		"1 maxcpus=1 noirqdistrib reset_devices"
352	
353	For s390x:
354		"1 maxcpus=1 cgroup_disable=memory"
355	
356	Notes on loading the dump-capture kernel:
357	
358	* By default, the ELF headers are stored in ELF64 format to support
359	  systems with more than 4GB memory. On i386, kexec automatically checks if
360	  the physical RAM size exceeds the 4 GB limit and if not, uses ELF32.
361	  So, on non-PAE systems, ELF32 is always used.
362	
363	  The --elf32-core-headers option can be used to force the generation of ELF32
364	  headers. This is necessary because GDB currently cannot open vmcore files
365	  with ELF64 headers on 32-bit systems.
366	
367	* The "irqpoll" boot parameter reduces driver initialization failures
368	  due to shared interrupts in the dump-capture kernel.
369	
370	* You must specify <root-dev> in the format corresponding to the root
371	  device name in the output of mount command.
372	
373	* Boot parameter "1" boots the dump-capture kernel into single-user
374	  mode without networking. If you want networking, use "3".
375	
376	* We generally don' have to bring up a SMP kernel just to capture the
377	  dump. Hence generally it is useful either to build a UP dump-capture
378	  kernel or specify maxcpus=1 option while loading dump-capture kernel.
379	
380	* For s390x there are two kdump modes: If a ELF header is specified with
381	  the elfcorehdr= kernel parameter, it is used by the kdump kernel as it
382	  is done on all other architectures. If no elfcorehdr= kernel parameter is
383	  specified, the s390x kdump kernel dynamically creates the header. The
384	  second mode has the advantage that for CPU and memory hotplug, kdump has
385	  not to be reloaded with kexec_load().
386	
387	* For s390x systems with many attached devices the "cio_ignore" kernel
388	  parameter should be used for the kdump kernel in order to prevent allocation
389	  of kernel memory for devices that are not relevant for kdump. The same
390	  applies to systems that use SCSI/FCP devices. In that case the
391	  "allow_lun_scan" zfcp module parameter should be set to zero before
392	  setting FCP devices online.
393	
394	Kernel Panic
395	============
396	
397	After successfully loading the dump-capture kernel as previously
398	described, the system will reboot into the dump-capture kernel if a
399	system crash is triggered.  Trigger points are located in panic(),
400	die(), die_nmi() and in the sysrq handler (ALT-SysRq-c).
401	
402	The following conditions will execute a crash trigger point:
403	
404	If a hard lockup is detected and "NMI watchdog" is configured, the system
405	will boot into the dump-capture kernel ( die_nmi() ).
406	
407	If die() is called, and it happens to be a thread with pid 0 or 1, or die()
408	is called inside interrupt context or die() is called and panic_on_oops is set,
409	the system will boot into the dump-capture kernel.
410	
411	On powerpc systems when a soft-reset is generated, die() is called by all cpus
412	and the system will boot into the dump-capture kernel.
413	
414	For testing purposes, you can trigger a crash by using "ALT-SysRq-c",
415	"echo c > /proc/sysrq-trigger" or write a module to force the panic.
416	
417	Write Out the Dump File
418	=======================
419	
420	After the dump-capture kernel is booted, write out the dump file with
421	the following command:
422	
423	   cp /proc/vmcore <dump-file>
424	
425	You can also access dumped memory as a /dev/oldmem device for a linear
426	and raw view. To create the device, use the following command:
427	
428	    mknod /dev/oldmem c 1 12
429	
430	Use the dd command with suitable options for count, bs, and skip to
431	access specific portions of the dump.
432	
433	To see the entire memory, use the following command:
434	
435	   dd if=/dev/oldmem of=oldmem.001
436	
437	
438	Analysis
439	========
440	
441	Before analyzing the dump image, you should reboot into a stable kernel.
442	
443	You can do limited analysis using GDB on the dump file copied out of
444	/proc/vmcore. Use the debug vmlinux built with -g and run the following
445	command:
446	
447	   gdb vmlinux <dump-file>
448	
449	Stack trace for the task on processor 0, register display, and memory
450	display work fine.
451	
452	Note: GDB cannot analyze core files generated in ELF64 format for x86.
453	On systems with a maximum of 4GB of memory, you can generate
454	ELF32-format headers using the --elf32-core-headers kernel option on the
455	dump kernel.
456	
457	You can also use the Crash utility to analyze dump files in Kdump
458	format. Crash is available on Dave Anderson's site at the following URL:
459	
460	   http://people.redhat.com/~anderson/
461	
462	
463	To Do
464	=====
465	
466	1) Provide relocatable kernels for all architectures to help in maintaining
467	   multiple kernels for crash_dump, and the same kernel as the system kernel
468	   can be used to capture the dump.

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Open Source Software for linux

Proprietary Software Open Source Alternative
Operating Systems
Microsoft Windows
Mac OS X
Ubuntu Linux
Fedora Linux
Centos (Red Hat Linux without Red Hat’s logos and support.)
openSUSE
Debian Linux
Mandriva Linux
Xandros
K12LTSP K12 Linux Terminal Server Project
VectorLinux
PC-BSD
There are too many others to list, go to Linux Online! for more distros!
Office Productivity Software / Suites
Microsoft Office OpenOffice (cross platform)
LibreOffice (cross platform)
KOffice – Linux
HTML Editors
Adobe Dreamweaver
Microsoft FrontPage
BlueGriffon (cross platform)
Digital Image / Photo Editing / Raster Image Editing Software
Adobe Photoshop GIMP (cross platform)
Image Viewers with RAW Capability
Photo Mechanic (Win and Mac OSX) Xee (Mac OSX only)
Vector Drawing Programs
Adobe Illustrator
Macromedia FreeHand
CorelDraw
Inkscape (cross platform)
2D CAD
(Computer Aided Drawing)
AutoCAD QCad (Linux/UNIX * Mac OS X)
3D CAD
(3D Modeling)
SolidWorks
Pro/ENGINEER
AutoDesk Inventor
Blender (cross platform)
BRL-CAD 3D
Povray 3D
Tulip 3D
Screen Recording
(to capture what you are doing on your computer and save as a video file)
CamStudio (for Windows only)
Desktop Publishing
Adobe Indesign
QuarkExpress
Microsoft Publisher
Scribus (cross platform)
PDF Creation
Adobe Acrobat PDF Creator (Windows only)OpenOffice

* This capability is built into Mac OS X via the print function.

Text Editors
Notepad jEdit (cross platform)
Notepad++ (for Windows only)
Syn (for Windows only)
Smultron (for Mac OS X only)
Web Servers
Microsoft IIS (Internet Information Services) Apache (cross platform)
Web Browsers
Microsoft Internet Explorer
Safari
Mozilla Firefox (cross platform)
Flock
Email Software
Microsoft Outlook
Microsoft Entourage
QuickMail
Thunderbird (cross platform)
Evolution
Kmail
FTP Clients
(File Transfer Protocol)
Ipswitch WS_FTP Pro
Fetch
Filezilla – FTP and SFTP (cross platform)
Cyberduck – FTP and SFTP (for Mac OS X only)
SFTP Programs
(SSH Secure File Transfer)
Filezilla – FTP and SFTP (cross platform)
Cyberduck – FTP and SFTP (for Mac OS X only)
WinSCP – SFTP and SCP client for Windows
SSH
PuTTY – SFTP and Telnet client for Windows
VNC
Apple Remote Desktop (ARD) TightVNC – VNC server and client for Windows, Linux, and Unix
Chicken of the VNC – VNC client for Mac OS X
OSXvnc – VNC server for Mac OS X
Hard Disk Utilities / Partitioning Tools
Norton PartitionMagic GParted & GParted LiveCD (Gnome Partition Editor) – (cross platform)
Anti-Virus Software
McAfee
Norton Anti-virus
AVG
ClamAV
ClamWin – (for Windows only)
ClamXav – (for Mac OS X only)
Keyboarding / Typing Software
Tux Typing 2
Edutainment / Educational Software
The KDE Edutainment Project
FREEDUC – resource for FOSS educational software
A List of Open Source Software for Education
Gcompris – educational softare for kids ages 2 to 10
Childsplay – various games for ages 1-9
KStars – a simualted planetarium (astronomy)
Kalzium – periodic table
KWord Quiz – flash cards
KTouch – teaches typing
Tux Paint – vector and raster image editing program for young children
KTurtle – Logo programming for young children
Math Programs
Geometer’s Sketchpad or Cabri GeoGebra – joins geometry, algebra and calculus
Dr. Geo – interactive geometry software
TuxMath – math game for kids
Music Composition
Rosegarden – similar to Cubase
Noteedit
Solfege – ear training
Montessori Bells
Sound Editing Programs
Sound Forge Audacity (cross platform)
Video Editing
iMovie KINO
Brainstorming, Mind Mapping, Flowcharting, Planning
Inpsiration FreeMind
Kivio
View Your Mind
Compression Utilities
WinZip 7-Zip
The Unarchiver
Accounting / Personal Finance
Quicken GnuCash
Grisbi – (cross platform)
Course Management Systems (CMS) and Virtual Learning Environments (VLE)
Click here for a full list of non-open source CMS/VLEs
Blackboard
WebCT
Campus Pipeline
ClassCampus
CyberProf
eCollege
Virtuoso
TeleTOP cms
Virtual Campus
Sentient Discover
MindEdge CMS
MyEDUkit
Click here for a full list of Open Source CMS/VLEs
Also click here
Moodle – used in 74 countries in 34 diferent languages!
MyClassroom – in use by several middle schools and high schools in the US and around the world!
interact
OpenCourse
Boddington
.LRN
LogiCampus
ATutor
Wordcircle CMS
Sakai
Manhattan
ILIAS
CourseWork – used by Stanford University
COSE (Creation of Study Environments)
Claroline – used in 62 countries and 28 languages!
WebWork
Eledge
ClassWeb 2.0
ePICE
Whiteboard
Student Information Systems (SIS)
Powerschool
WebEIM
eSIS
SCHOOLMASTER
MMS
Centre
Open Admin for Schools
Emulators
Virtual PC for Mac QEMU
PearPC
Q – cocoa port of QEMU for Mac OS X
bochs
Virtualization
Virtual PC for Windows
VMware
VirtualBox (cross platform)
coLinux

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skills for linux administrator

User & group administration
Configuring Linux Networking
Installing and configuring Linux Operating system
Basic Operating System Concepts
Basic experience in Shell Scripts.
Knowledge on apache server
Knowledge on FTP,SSH,SSL,Telnet & xinetd
Knowledge about File system hierarchy
Basic Network Troubleshooting
Installing & configuring Linux Software
Monitoring Server Performance
Configuring Linux Software RAID
Expanding Linux Partitions with LVM
Network Based Linux Installation like NFS, HTTP & FTP
In-depth knowledge on Linux operating system
Experience in shell and Perl scripting
Kernel compilation and fine tuning.
Configuring Linux Firewalls Using iptables
Configuring & Managing Disk Usage With Quotas
Knowledge on TCP/IP
File system Management
Expertise in managing and configuring various services like DNS, NIS, NFS, APACHE, FTP, DHCP & SAMBA
Knowledge on High Availability and Clustering.
High Level of Troubleshooting skill

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Open Source Content Management Systems

A content management system (CMS) is a system facilitating efficient production of desired output by using managed content. The content may be text, images, graphics, documents, sound, video or other that can be managed in an electronic format. It is a software application used in uploading, editing and managing content on a website. CMS has been gaining popularity as it handles various tasks including when to display content, how many times to display content to specific users and how the content interacts with other elements of the website. Open source CMS systems are popular for their quality, lower cost, reliability and flexibility.
This article is the first in a series that lists the advantages and disadvantages of the 18 most popular open source Content Management Systems. The first five are WordPress, Joomla, Drupal, Magento, and b2evolution.

 

1. WordPress
WordPress is a publishing platform focused on aesthetics, web standards, and usability. Working with WordPress does not require any knowledge of HTML. Ease of installation and upgrading make it a great fit for beginner webmasters and even for non-developers.
Using WordPress has these advantages to users:

  • The CMS tool has blogging options such as Posts, comments, media, links, simple pages, users etc.
  • Customization of the look of a website or addition of an extra feature is possible
  • Multilingual support: Although it lacks out of the box support for bilingual or multilingual blogs, plugins developed by the WordPress community permit creation of a multilingual blog
  • Many plugins are released by independent developers that enhance the user interface
  • Creation of new content is very easy with the visual text editor
  • Security from hackers is comparatively high for many community developers

Disadvantages are:

  • Limitations for bigger and more complicated sites
  • Better suited for blogs than general websites
  • Changing navigational structure requires knowledge of WP scripting language and CSS
  • Below average SEO friendly: SEO provided by WordPress is below average but can be improved with installation of a useful plugin
  • Attracts spambot

2. Joomla
Joomla is a much appreciated portal- or community type site CMS tool for simple websites and blogs. It comes with an easy to use graphical administrative interface and powerful WYSIWYG Editor that enables the creation and editing of pages. With Joomla, there is no need to use specialized tools or programming languages to update the sites. It has a large user base with a lively community where tips and tricks are shared.
Advantages of using Joomla as CMS tool are as follows:

  • Good choice for creating a community or network with a membership area, newsroom, forums, articles, input from external authors
  • Simple installation: takes a few minutes
  • In the most recent version of Joomla, a more complex navigation pattern is available that can support more than two-level hierarchies
  • A lot of functionality is built into Joomla hence it requires fewer plugins than WordPress
  • Easy to create a navigation structure: no need to have knowledge of Joomla scripting while changing the navigation structure and menus of the site
  • No knowledge of HTML is required
  • Multilingual Support: An extra module called Joomfish is required to facilitate multilingual support
  • Allows users to set article expiration dates, activation dates, author names, etc.
  • Has many development tools and tutorials to help users
  • Offers users a large community where advice, tips and tricks can be shared

Disadvantages of using Joomla:

  • Lacks advanced technologies hence not suitable for advanced web designers
  • Less security: Every site has its own login details making the work easier but leaving the site less secured
  • Less friendly to Search engine optimization
  • Certain plug-ins cost money which are available for free in WordPress

3. Drupal
Drupal is a free source PHP based CMS tool that allows an individual or a community of users to easily publish, manage and organize content on a website. Requiring complete control over scripting of sophisticated website design, Drupal is not very user friendly, but can be worked on only by professional web developers. Installation of Drupal is easy and straight forward for anyone familiar with installing applications on web servers. For web developers new to Drupal, it is a steep learning curve. It requires knowledge of a sophisticated programming language.
Drupal has gained popularity over other CMS for the following advantages:

  • Flexible yet robust content creation: There is flexibility in creating and managing different content types such as text, blogs, video, polls etc.
  • Using Drupal CMS, one can customize the URL path for each piece of content published on a website
  • Creation of own dynamic designs for pages of your own website
  • Drupal is the ideal platform for developing large websites with hundreds of pages
  • Highly scalable
  • Drupal is proven and secured
  • Multilingual Support: It requires only to activate a core module named Locale to enjoy multilingual support
  • SEO friendly: Drupal CMS software is ideal for search engine optimization
  • It has very strong community support
  • Large support base

Disadvantages of Drupal include following:

  • Not very user friendly and requires greater technical knowledge
  • Needs MySQL and Php language support
  • Customization of Drupal requires an expert user and developer

4. Magento
Magento is an open source ecommerce platform designed for customizing, managing and running an online portal.
Advantages of Magento include:

  • Well defined with core code and third party or community code allowing users to download other extensions or modules without worrying about the impact of future upgrades and or disrupting the current appearance of the website
  • SEO friendliness: Magento achieves high ranking on search engines Google and Bing
  • Large community of users: A community of users, developers and service providers are available to share their advice, tips and tricks
  • PHP written Magento is a feature rich ecommerce platform. It has all the features of a top of the line Ecommerce website such as advanced promotion and marketing tools.
  • Easy integration of additional layouts and Add-ons
  • Provides ability to manage multi stores from single Administration panel
  • Nice default template

Disadvantages are:

  • The CMS software is a complicated platform and follows best web programming practices
  • There are very few expert Magento developers available
  • Heavily layered and overly complicated coding style and large number of files required to learn and do customization

5. b2Evolution

B2Evolution is an open source blogging system distributed under the GNU General Public License, making it free to use and modify. A large number of plug-ins have been developed for the CMS including extensions allowing incorporation of third-party text editors. In addition, it also permits integration of functionality provided by popular websites including MySpace, YouTube, Digg etc. It is featured with friendly URLs, image resizing, photoblogs with thumbnails, UI levels, a WYSIWYG editor, spell check and style wizard. It is a multilingual, multi user, multi blog publishing CMS.
Advantages of b2Evolution:

  • Fast and easy installation of the software: can be installed on virtually any server configuration consisting of PHP and MySQL
  • Spam protection: Featured with blacklisting and CAPTCHA to prevent comments from automated bot programs, your blog will be free from annoying spam comments
  • B2Evolution provides multiple Theme support
  • Navigation is quite straight forward
  • Installation of plugins is quite simple

Disadvantages:

  • Difficult for non-technical blogger to use b2Evolution
  • Performing customization requires knowledge of the language of the PHP tribe
  • With  respect to availability of extensions and their ease of use, Add-on community is limited
  • User community is comparatively small
6. Xoops
Xoops (eXtensible Object Orientated Portal System) is an open source and ideal tool to develop small to large dynamic community web sites, corporate portals, web logs and much more. It is a dynamic object oriented portal script that is written in PHP and it supports MySQL. Easy to use, Xoops is an ideal tool to create data-driven community sites of all sizes. It is used for blogs, corporate intranet sites and content-rich information portals.
Advantages of Xoops:

  • Small learning curve
  • Easy installation
  • Addition of features to your website can be done easily through additional modules and themes
  • It has worldwide support available in a number of languages
  • Administrator can easily find users based on a variety of criteria.  Using a simple template-based system, he can send both emails and private messages
  • Using a theme-based template system, Xoops allows instant enhancing of the presentation of your site
  • Search Engine Friendly: Xoops supports many add-ons to help make your site more search engine-friendly
  • Theme capability
  • Worldwide Support

Disadvantages:

  • A provider should be equipped with the Apache web server, PHP and an SQL database, preferably MySQL
  • It requires installation of a number of modules and some of the documents for some modules are lacking. Because of this, it becomes time consuming for administrators to tweak these modules to get them to work.

7. Seotoaster
SEO Toaster is a free open source CMS and e-commerce software used by many big and small businesses. The powerful CMS is very light on resource usage. It represents an alternative to Yahoo Stores for small e-commerce websites or WordPress when used as a corporate or affiliate CMS. Featured with a unique architecture, the powerful CMS makes piloting SEO execution. It also helps in easy marketing for multiple websites from a central automated web marketing location. Seotoaster requires a single core to power and revise multiple websites hosted on the same server.
Advantages:

  • Provides ability to access a library of ready-to-use themes to jump-start your presence online
  • Customize and integrate open source shopping cart and other applications
  • Building one, two and more money-making websites for free is possible with SEO Toaster
  • SEO friendliness: In-built all latest SEO techniques right into their website from the get-go helps in achieving high rankings with Google and other search engines: No blog to read or SEO expert fees to pay
  • Much easier to use than WordPress and has scope of scalability
  • Seotoaster is easy for content writers, and website administrators featuring complete front-end edition

8. e107

e107 is an open source content management system covering every area of content management including admin, file and directory management, multimedia, e-commerce and so on. It is embed with simple, intuitive interface and flexible architecture which allows the CMS to perform well on anything ranging from blogs and personal websites to business sites and intranets.
Advantages of popular e107:

  • Loads of plugins available on the CMS
  • Easy to install
  • Great community support
  • Designers are available to create beautiful theme designs
  • Highly customizable

Disadvantages:

  • Not many plugins are available for bloggers

9. Concrete5
Concrete5 is a free open source CMS gaining popularity among designers for its focus on ease of use. With Concrete5, one can manage a small to medium size website as easy as a WYSIWYG. A great feature of Concrete5 is it keeps revising a page which make it easy to roll back to a previous version of the page.
Advantages include:

  • The Concrete5 platform is quite flexible and easy to edit and update
  • Best for non-programmers that want a static website
  • Creating themes with Concrete5 is very easy
  • SEO friendly
  • Multilingual support
  • One can develop own themes

Disadvantages include:

  • It needs solid knowledge of HTML/CSS and an acquaintance with PHP
  • Community is not very large
  • It needs a blank database, which can be frustrating if on a shared hos

10. Typo3
 TYPO3 is an open source enterprise-class content management system. The powerful TYPO3 can handle large and complex websites. It has a broad base of extensions and developers that can add to its functionality. A developer is able to create pages with a variety of content elements such as regular text, forms, multimedia, file links, etc. Advantages include:

  • Many extensions
  • Powerful scripting allows flexibility without custom PHP plugins
  • Unlimited scalability: Typo3 can acquire new functionality and expand or modify existing ones with special modules
  • The CMS allows working with draft versions of web site without affecting live site content
  • Unlimited Undo/History levels make it possible to roll back your changes to a previous state, regardless of how old that stage is
  • Multiple domains/sites on one installation: Single Typo3 installation facilitates working on several web sites with different domains. This is useful when your sites have shared or related content or when these sites belong to one complex project
  • Gives the ability to temporarily hide some content without deletin
  • Huge international developer community
  • Multilingual
  • Security: A high level of protection from hacker attacks or hijacking of business-critical company websites is offered

Disadvantages:

  • Learning typoscript is time consuming
  • The documentation lacks detail and needs more examples
  • It’s not suitable for small websites
  • Many extensions haven’t been updated in years

11. Media Wiki
MediaWiki is a PHP designed open source software wiki package, initially built for use on Wikipedia. Now it is used by several other projects of the non-profit Wikimedia Foundation and by many other wikis, including this website, the home of MediaWiki. The free software is available under the license of the GPL. It runs on a LAMP (Linux, Apache, MySQL, PHP) architecture. It’s designed to run on large server farms for websites that get millions of hits per day.
Advantages include:

  • Scalability: It is scalable and powerful, with many features not commonly found in Wiki systems
  • MediaWiki supports a multiple server environment allowing it to scale up for high usage situations such as massive collaborations
  • Powerful and robust, MediaWiki is capable of handling hundreds of millions of pages
  • Multiple users can simultaneously update, modify and edit pages on the CMS which is designed for a collaborative environment



12. Movable Type
Movable Type is a free, all-in-one content management system that helps in building and operating an eCommerce site and creating a social networking site. It also lets developers manage large volumes of content and run a blog, while also functioning as an intranet. This content management system has gained popularity in various circles including media and publishing companies, design and development firms, power bloggers and marketing and communications folks.
Advantages include:

  • Managing your website with Movable Type is quite easy through the administrator interface
  • With one installment, one can manage multiple websites/blogs
  • It is scalable. As your site grows, the platform scales to meet fluctuating traffic needs
  • It is quick and easy to make new templates and requires very little technical knowledge using the built-in tools
  • It’s easy to publish content in either entry or page form and add custom fields as you go
  • Optional support for bloggers, online support for businesses and premium support for enterprise and high-traffic bloggers
  • It supports multiple users, themes, comments and tagging

Disadvantages include:

  • It takes longest time to install in comparison to other CMS
  • Active community is significantly smaller than more popular content management systems

13. DotCMS
DotCMS is an enterprise-grade open source J2EE/Java Web Content Management System. It is used for controlling websites and managing content such as media, modules, text and other add-ons. Users with moderate or no technical ability can make massive changes on a site while working on dotCMS. The combination of open source and Java Script makes it sophisticated, innovative and customizable. Intended to serve CMS-driven e-commerce, it allows corporations, institutions and organizations to move at a quicker pace without the need for Java development talent within a Web Team. Some of the organizations that run on dotCMS Enterprise Edition are Toyota, Hospital Corporation of America, University of Texas, Thomson Reuters, Aquent, State of Ohio, and the Government of Quebec.

Advantages include:

  • It offers a certified and warranted Enterprise solution in addition to a Community version
  • Using dotCMS, clients with little or no technical knowledge can manage an open source portal, company web site, or intranet application
  • It is suitable for a document management application, or an information portal of any type
  • dotCMS enables the marketing department to tag, segment and group site visitors by any number of criteria. For example by the pages they visit, the time of their last visit, their demographic information and any of their indicated interests

Disadvantages include:

  • Unlike other open source CMS, dotCMS requires one to have root access to the server for installation of things like Apache Tomcat

14. Dotclear
Dotclear is a French open source CMS under the GNU General Public License. It is a blogging platform available in English. Developers can create multiple blogs with one installation. The open-source web publishing software offers a very user-friendly backend. Anyone with little technical knowledge can publish on the web using Dotclear, a user-friendly tool.
Advantages include:

  • Easy publication
  • Package engine allows 1-click install for plug-ins and themes
  • Fully customizable theme
  • User-friendly administration
  • Low requirements (PHP4/MySQL4) help to minimize hosting dependencies
  • Flexible comment system
  • Performance and scalability
  • Huge number of available plug-ins

Disadvantages include:

  • Single-site only
  • Rudimentary security features
  • Not suitable for large enterprise projects
  • Very limited assets manager



15. Zope/Plone 

Plone is an open source and web CMS that is based on the Zope application server, which uses the Python language. This is unique in a world filled with PHP applications. It is famous among developers as an intranet, portal, web site or community site. It helps them to manage all sorts of content, organized into folders that can be uploaded by a community of users.
Advantages include:

  • Far less vulnerability than PHP-based systems
  • Extremely extensible and flexible
  • Wide range of 3rd-party products to deal with off-norm use-cases
  • Extraordinarily helpful community
  • Excellent i18N support
  • Scalability: Plone scales to enterprise levels
  • World-wide availability of professional trainers and consultants
  • More secure than systems like Drupal and Joomla

Disadvantages include:

  • Requires knowledge of Zope and Python
  • Not very user friendly for non-technical users
  • Plone’s CMS niche is often confused with other, less powerful OSS CMS due to its operation at the confluence of web content management, social S/W & collaboration, and enterprise portals
  • Very steep learning curve
  • Not very good web 2.0 support (blogs, forums, streaming media etc.)

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Monitoring Disk Usage In Linux

One of the routine job of a Linux administrator to monitor the Disk space continuously. Normal people will write a simple script to check the disk space and report to system administrator through email. Good Idea,but here i am telling a new one which will continuously monitor your Disk and report if it cross a preset value. This will run as a cronjob.

#!/bin/bash
#Script for monitoring Disk Usage
#Author BipinDas,Arab Open University.
ADMIN=”yourname@yourdomain.com”
# set alert level 80% is default
ALERT=80
df -H | grep -vE ‘^Filesystem|tmpfs|cdrom’ | awk ‘{ print $5 ” ” $1 }’ | while read output;
do
#echo $output
usep=$(echo $output | awk ‘{ print $1}’ | cut -d’%’ -f1 )
partition=$(echo $output | awk ‘{ print $2 }’ )
if [ $usep -ge $ALERT ]; then
echo “Running out of space \”$partition ($usep%)\” on $(hostname) $(hostname -i) as on $(date)” |
mail -s “Alert: Almost out of disk space $usep ” $ADMIN
fi
done

Save it as disk_monitor.sh in your scripts folder.

Open Crontab Editor

vi /etc/crontab

*/5 * * * * root /path/to/script/disk_monitor.sh

Perfect,This will frequently check your Disk and inform once it cross the limit.

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Linux Basic Commands-Suresh Dangi

changing directory / to /etc

[root@pc1 /]# cd /etc

One step back /etc to /

[root@pc1 etc]# cd ..

Go to previous working directory

[root@pc1 /]# cd –

Go to current login user home directory

[root@pc1 etc]# cd ~

Show the contents of /etc in single color

[root@pc1 ~]# dir /etc

Show the contents of /etc in different colors with nature of contents

[root@pc1 ~]# Ls /etc

create a folder on root partition

[root@pc1 ~]# mkdir /disk

Create a folder in /disk

[root@pc1 ~]# mkdir /disk/dir

Create multiple folder in multiple directories with single command

[root@pc1 ~]# mkdir /etc/dir1 /var/dir2 /usr/dir3

Create multiple folder in same directory

[root@pc1 ~]# mkdir dir1 dir2 dir3

Copy a file in directory

[root@pc1 disk]# cp file dir

Copy a file from /disk/file and paste it in /disk/dir/

[root@pc1 disk]# cp /disk/file /disk/dir

Copy a directory with –r option

[root@pc1 disk]# cp -r dir dir2

Copy a file from /disk/file and paste it in /etc with myfile name

[root@pc1 disk]# cp /disk/file /etc/myfile

Remove a file

[root@pc1 disk]# rm file

Remove a file with forcefully option

[root@pc1 disk]# rm –f file

Remove a directory with out –r option and you face will an error

[root@pc1 disk]# rm dir

Remove a directory with –r option

[root@pc1 disk]# rm -r /disk

Remove a directory with forcefully option

[root@pc1 disk]# rm -rf dir

Move /etc/dir1 to /disk/ with different name

[root@pc1 disk]# mv /etc/dir1 /disk/mydir

Rename the folder name mydir to dir

[root@pc1 disk]# mv /disk/mydir /disk/dir

Rename the file name with myfile

[root@pc1 disk]# mv file myfile

Read a file page by page with less command

[root@pc1 disk]# less /etc/grub.conf

Read a file page by page with more command

[root@pc1 disk]# more /etc/qrub.conf

Read first ten lines of grub.conf

[root@pc1 disk]# head /etc/grub.conf

Read last ten lings of grub.conf

[root@pc1 disk]# tail /etc/grub.conf

Read first 12 lines with –n option

[root@pc1 disk]# head -n 12 /etc/grub.conf

Read last 11 lines with –n option

[root@pc1 disk]# tail -n 11 /etc/grub.conf

Copy the contents of /etc/grub.conf in /disk/file

[root@pc1 disk]# cat /etc/grub.conf > /disk/file

Append the contents /etc/mtab in /etc/file

[root@pc1 disk]# cat /etc/mtab >> /disk/file

Merging tow commands with pipe sign output of the first command is input of second command

[root@pc1 disk]# cat /etc/squid/squid.conf I more

Count the total lines of squid.conf

[root@pc1 disk]# cat /etc/squid/squid.conf I wc -L

Show only spool words in squid.conf

[root@pc1 disk]# cat /etc/squid/squid.conf I grep spool

Flush the contents of file

[root@pc1 disk]# cat /dev/null > /var/log/messages

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