Solutions for fixing Windows errors - Part 2
Hotfixes for Windows XP SP3
Please find below the links for downloading windows service packs:
Do take backups of important files before installing any of these service packs.
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Solutions for fixing Windows errors - Part 1
Please find below links to some softwares and other tricks to fix windows errors:
Utilities (Softwares and tricks)
* Windows Event viewer - using this built-in tool, you can view the system event log and see error message that my not be displayed to the user. This can be incredibly useful in your detective work.
* Microsoft Dependency Walker - great free tool that will allow you to gather a list of all DLLs used or required by a program or other DLL. This can be a life-saver.
* Ad-Aware by LavaSoft
* Windows XP Recovery Console - can be used to restore files from the XP installation dis.
* Sysinternals Process Explorer
* Windows XP 'emergency repair' procedure - when things get really dicey
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Relational Database - Codd's Rules
Relational Database - Codd's Rules !!!
A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd. Most popular commercial and open source databases currently in use are based on the relational database model.
A short definition of an RDBMS may be a DBMS in which data is stored in the form of tables and the relationship among the data is also stored in the form of tables.
Codd's Rules
- All database management must take place using the relational database's innate functionality
- All information in the database must be stored as values in a table
- All database information must be accessible through the combination of a table name, primary key and column name.
- The database must use NULL values to indicate missing or unknown information
- The database schema must be described using the relational database syntax
- The database may support multiple languages, but it must support at least one language that provides full database functionality (e.g. SQL)
- The system must be able to update all updatable views
- The database must provide single-operation insert, update and delete functionality
- Changes to the physical structure of the database must be transparent to applications and users.
- Changes to the logical structure of the database must be transparent to applications and users.
- The database must natively support integrity constraints.
- Changes to the distribution of the database (centralized vs. distributed) must be transparent to applications and users.
- Any languages supported by the database must not be able to subvert integrity controls.
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What are Port Numbers
Port Numbers - Linux
PORTS NUMBERS : Just as the physical address (MAC address) and the logical address (IP address) helps to route the traffic to a particular machine on a network, it is the port that identifies which service on the machine this traffic is destined to.
List of ports : /etc/services
A port on a specific computer is called a socket. It can be open, closed, listening or have a connection established.
###Important PORT NUMBERS to remember:
20 - FTP - data transfer
21 - FTP - control (command)
22 - SSH
23 - Telnet
25 - SMTP
37 - Time
43 - WHOIS
42 - WINS
53 - DNS
67 - BOOTp
68 - DHCP
69 - TFTP
79 - FINGER
80 - HTTP (WWW)
88 - Kerberose
101 - HOSTNAME
110 - POP3
111 - rpcbind
119 - NNTP
123 - NTP (Time)
137 - NetBios (nmbd)
139 - NetBios ( Samba)
143 - IMAP/Dovecot
161 - SNMP
180 - RIS
220 - IMAP3
389 - LDAP
443 - HTTPs
500 - Internet Key Exchange (IKE), IPSec
520 - RIP
546 - DHCPV6 client
547 - DHCPV6 server
554 - rtsp(Real Time Stream Protocol, Audio/Video)
631 - Printing (ipp)
744 - Flexlm
901 - SWAT
953 - rndc
993 - IMAPSecure
995 - POPs
999 - POP over SSL/TLS
2049 - NFS
2082 - CPANEL
2083 - CPANEL Secure SSL/TLS
2086 - CPANEL WHM
2087 - CPANEL WHM Secure/SSL
2095 - CPANEL Webmail
2096 - CPANEL Webmail Secure/SSL
2222 - Direct Admin Control Panel
2401 - CVSP server
3268 - AD Global Catalog
3269 - AD Global Catalog over SSL
3306 - MySQL Server
3389 - Terminal services (rdp-remote desktop protocol)
4643 - Virtusso Power Panel
(6000 - X11
6063)
8443 - Pleask Control Panel
9999 - Urchin
10000- Webmin Control Panel
21018- Skype
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Disk Quotas in linux
Disk Quotas
Disk space can be restricted by implementing disk quotas which alert a system administrator before a user consumes too much disk space or a partition becomes full. Disk quotas can be configured for individual users as well as user groups. This makes it possible to manage the space allocated for user-specific files (such as email) separately from the space allocated to the projects a user works on (assuming the projects are given their own groups).
In addition, quotas can be set not just to control the number of disk blocks consumed but to control the number of inodes (data structures that contain information about files in UNIX file systems). Because inodes are used to contain file-related information, this allows control over the number of files that can be created.
* Features of quotas
1). Limits disk usage (blocks or inodes)
2). Tied to file systems (et on a per file system basis)
3). can be configured for users and groups
* Steps to enable quota support :-
1) Enable quota support per file system in : /etc/fstab
a) defaults,usrquota,grpquota
Example:
#vi /etc/fstab
/dev/Volgroup00/logVol02/home ext3 defaults,usrquota,grpquota 1 2
2) Remount the file system(s)
a) mount -o remount /
b) use 'mount' to confirm that 'usrquota, grpquota' support are enabled
Example:
#mount -o remount /home
3) Create quota database files and generate disk usage table
a) quotacheck -mcug / (where c-create, u-user, g- group)
This creates /aquota.user and aquota.group
b) quotacheck -mavu
4) Assign quota policies: a) edquota username (set blocks/inodes, soft_limits, hard_limits)
Example:
edquota student1 (sets quotas for user student1)
b) edquota -g devl
(for group quota, check using #quota -g devl)
5) Check quotas
#quota username
Example:
#quota student1
6) Report on usage
#repquota -a
==> The blocks are measured in 1K increments, eg 20000 blocks is roughly 20 MB.
* To change the grace period of quota
#edquota -t
* Managing quotas
If quotas are implemented, they need some maintenance-mostly in the form of watching to see if the quotas are exceeded and making sure the quotas are accurate.
a) Enabling and disabling quotas
i) To turn all user and group quotas off
#quotaoff -vuag
If neither the -u and -g options are specified, only the user quotas are disabled. If only -g is specified, only group quotas are disabled. The -v switches causes verbose status informtion to display as the command executes.
ii) To enable quotas again:
#quotaon -vaug
To enable quotas for a specific file system, such as /home, use the following
#quotaon -vug /home
If neither the -u or -g options are specified, only the user quotas are enabled. If only -g is specified, only group quotas are enabled.
b) Reporting on Disk Quotas
#repquota -a
c) Keeping Quotas accurate Whenever a file system is not unmounted clearly (due to a system crash, for eg), it is necessary to run quotacheck. Running the following command periodically keeps the quotas more accurate.
#quotacheck -avug
The easiest way to run it periodically is to use cron.
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