Archive for the ‘Debian’ Category
July 21st, 2010 | 
Author: This is a list of handy MySQL commands that I use frequently.
Below when you see # it means from the unix shell. When you see mysql> it means from a MySQL prompt after logging into MySQL.
To login (from unix shell) use -h only if needed.
# [mysql dir]/bin/mysql -h hostname -u root -p
Create a database on the sql server.
mysql> create database [databasename];
List all databases on the sql server.
mysql> show databases;
Switch to a database.
mysql> use [db name];
To see all the tables in the db.
mysql> show tables;
To see database’s field formats.
mysql> describe [table name];
To delete a db.
mysql> drop database [database name];
To delete a table.
mysql> drop table [table name];
Show all data in a table.
mysql> SELECT * FROM [table name];
Returns the columns and column information pertaining to the designated table.
mysql> show columns from [table name];
Show certain selected rows with the value “whatever”.
mysql> SELECT * FROM [table name] WHERE [field name] = "whatever";
Show all records containing the name “Bob” AND the phone number ‘3444444′.
mysql> SELECT * FROM [table name] WHERE name = "Bob" AND phone_number = '3444444';
Show all records not containing the name “Bob” AND the phone number ‘3444444′ order by the phone_number field.
mysql> SELECT * FROM [table name] WHERE name != "Bob" AND phone_number = '3444444' order by phone_number;
Show all records starting with the letters ‘bob’ AND the phone number ‘3444444′.
mysql> SELECT * FROM [table name] WHERE name like "Bob%" AND phone_number = '3444444';
Show all records starting with the letters ‘bob’ AND the phone number ‘3444444′ limit to records 1 through 5.
mysql> SELECT * FROM [table name] WHERE name like "Bob%" AND phone_number = '3444444' limit 1,5;
Use a regular expression to find records. Use “REGEXP BINARY” to force case-sensitivity. This finds any record beginning with a.
mysql> SELECT * FROM [table name] WHERE rec RLIKE "^a";
Show unique records.
mysql> SELECT DISTINCT [column name] FROM [table name];
Show selected records sorted in an ascending (asc) or descending (desc).
mysql> SELECT [col1],[col2] FROM [table name] ORDER BY [col2] DESC;
Return number of rows.
mysql> SELECT COUNT(*) FROM [table name];
Sum column.
mysql> SELECT SUM(*) FROM [table name];
Join tables on common columns.
mysql> select lookup.illustrationid, lookup.personid,person.birthday from lookup left join person on lookup.personid=person.personid=statement to join birthday in person table with primary illustration id;
Creating a new user. Login as root. Switch to the MySQL db. Make the user. Update privs.
# mysql -u root -p
mysql> use mysql;
mysql> INSERT INTO user (Host,User,Password) VALUES('%','username',PASSWORD('password'));
mysql> flush privileges;
Change a users password from unix shell.
# [mysql dir]/bin/mysqladmin -u username -h hostname.blah.org -p password 'new-password'
Change a users password from MySQL prompt. Login as root. Set the password. Update privs.
# mysql -u root -p
mysql> SET PASSWORD FOR 'user'@'hostname' = PASSWORD('passwordhere');
mysql> flush privileges;
Recover a MySQL root password. Stop the MySQL server process.
Start again with no grant tables.
Login to MySQL as root.
Set new password.
Exit MySQL and restart MySQL server.
# /etc/init.d/mysql stop
# mysqld_safe --skip-grant-tables &
# mysql -u root
mysql> use mysql;
mysql> update user set password=PASSWORD("newrootpassword") where User='root';
mysql> flush privileges;
mysql> quit
# /etc/init.d/mysql stop
# /etc/init.d/mysql start
Set a root password if there is on root password.
# mysqladmin -u root password newpassword
Update a root password.
# mysqladmin -u root -p oldpassword newpassword
Allow the user “bob” to connect to the server from localhost using the password “passwd”. Login as root. Switch to the MySQL db. Give privs. Update privs.
# mysql -u root -p
mysql> use mysql;
mysql> grant usage on *.* to bob@localhost identified by 'passwd';
mysql> flush privileges;
Give user privilages for a db. Login as root. Switch to the MySQL db. Grant privs. Update privs.
# mysql -u root -p
mysql> use mysql;
mysql> INSERT INTO db (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,Create_priv,Drop_priv) VALUES ('%','databasename','username','Y','Y','Y','Y','Y','N');
mysql> flush privileges;
or
mysql> grant all privileges on databasename.* to username@localhost;
mysql> flush privileges;
To update info already in a table.
mysql> UPDATE [table name] SET Select_priv = 'Y',Insert_priv = 'Y',Update_priv = 'Y' where [field name] = 'user';
Delete a row(s) from a table.
mysql> DELETE from [table name] where [field name] = 'whatever';
Update database permissions/privilages.
mysql> flush privileges;
Delete a column.
mysql> alter table [table name] drop column [column name];
Add a new column to db.
mysql> alter table [table name] add column [new column name] varchar (20);
Change column name.
mysql> alter table [table name] change [old column name] [new column name] varchar (50);
Make a unique column so you get no dupes.
mysql> alter table [table name] add unique ([column name]);
Make a column bigger.
mysql> alter table [table name] modify [column name] VARCHAR(3);
Delete unique from table.
mysql> alter table [table name] drop index [colmn name];
Load a CSV file into a table.
mysql> LOAD DATA INFILE '/tmp/filename.csv' replace INTO TABLE [table name] FIELDS TERMINATED BY ',' LINES TERMINATED BY '\n' (field1,field2,field3);
Dump all databases for backup. Backup file is sql commands to recreate all db’s.
# [mysql dir]/bin/mysqldump -u root -ppassword --opt >/tmp/alldatabases.sql
Dump one database for backup.
# [mysql dir]/bin/mysqldump -u username -ppassword --databases databasename >/tmp/databasename.sql
Dump a table from a database.
# [mysql dir]/bin/mysqldump -c -u username -ppassword databasename tablename > /tmp/databasename.tablename.sql
Restore database (or database table) from backup.
# [mysql dir]/bin/mysql -u username -ppassword databasename < /tmp/databasename.sql
Create Table Example 1.
mysql> CREATE TABLE [table name] (firstname VARCHAR(20), middleinitial VARCHAR(3), lastname VARCHAR(35),suffix VARCHAR(3),officeid VARCHAR(10),userid VARCHAR(15),username VARCHAR(8),email VARCHAR(35),phone VARCHAR(25), groups VARCHAR(15),datestamp DATE,timestamp time,pgpemail VARCHAR(255));
Create Table Example 2.
mysql> create table [table name] (personid int(50) not null auto_increment primary key,firstname varchar(35),middlename varchar(50),lastnamevarchar(50) default 'bato');
This post will explain how to disable IPv6 in a system running Debian GNU/Linux or Ubuntu Linux.
You should want to disable IPv6 for compatibility reason or if you not plan to use it for speed up your system and/or to avoid loading of unuseful modules on system start up.
For disable the protocol you have to edit
/etc/modprobe.d/aliases
file and change two lines as follow :
#alias net-pf-10 ipv6 net-pf-10 off
You should also tell to your kernel to not load IPv6 module by blacklisting it at the boot, for doing so edit
/etc/modprobe.d/blacklist
file adding the following line :
blacklist ipv6
Reboot your system and check with the following command if the module ipv6 is not present :
lsmod |grep ipv6
You’ve done
Hope this help
Bye
Riccardo
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Very often it happens that I must give support to a colleague or a customer on a Linux machine.
It’s very difficult to spell all bash command I will use to check which could be the problem, especially by phone.
When I discover “screen” it was a revelation.
With screen http://www.gnu.org/software/screen/screen.html you should share a linux session with other people.
You should use screen by simply ask to the user you want to assist to type on the console the following command :
screen
So if you can connect to the machine (even with ssh) you should run the following command :
screen -x
to share the same bash session.
Hope this help
Bye
Riccardo
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In some situation you may want to avoid loading a Linux driver module automatically . For example:
- In some cases buggy driver causes kernel BUG or system fault on load so you just want to avoid the problem.
- If your system connected without a diskette / floppy drive; kernel will try to load floppy driver – disable floppy driver or module.
The Linux kernel get module information on boot from /etc/modprobe.conf file and /etc/modprobe.d/* file(s).
If you are using RHEL or CentOS do the following :
open your /etc/modprobe.conf file and turn of auto loading using following syntax:
alias driver-name off
If you are using Debian or Ubuntu do the following :
open /etc/modprobe.d/blacklist file and add driver name using following syntax:
blacklist driver-name
Reboot your system and use lsmod command to show the status of modules in the Linux Kernel.
Hope this help
Bye
Riccardo
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This post will explain how to configure a DHCP Server running on Ubuntu Server 9.04 (Jaunty Jackalope) for more than one interfaces and more than one network.
This post assume you have :
- A private network with 192.168.123.0/24
Three network on which you have to assign dinamic IP Addresses, for example a LAB network, an SUP Network (Support) and a WIFI network with the following subnet.
- 192.168.124.0/24 (sup)
- 192.168.125.0/24 (lab)
- 192.168.127.0/24 (wifi)
This post also assume you have a system running ubuntu (or debian) with four (4) NIC each one connected to one of the network above, and you will have the following configuration :
SUP network
Server IP Address : 192.168.124.1
DHCP Scope : 192.168.124.100 – 192.168.124.200
Gateway : 192.168.124.254
LAB network
Server IP Address : 192.168.125.1
DHCP Scope : 192.168.125.100 – 192.168.125.200
Gateway : 192.168.125.254
WIFI network
Server IP Address : 192.168.127.1
DHCP Scope : 192.168.127.100 – 192.168.127.200
Gateway : 192.168.127.254
The name server for all the networks will be a server in the internal network (192.168.123.2).
First of all you have to install DHCP server, for doing so, type :
sudo apt-get install dhcp3-server
This post will explain hot-to configure a unique IP Address on multiple NICs (Phisical or Virtual) on Debian GNU/Linux (with a 2.6 kernel).
This post assume you have a 192.168.0.0/24 network and that you want to assign 192.168.0.10/24 to your system.
Read the rest of this entry »
Ethernet bonding refers to aggregate multiple ethernet channels together to form a single channel. This is primarily used for redundancy in ethernet paths or for load balancing. This page refers to ifenslave mode in particular to configure ethernet bonding on Linux systems, and so doesn’t limit itself to discussion of 802.3ad Trunk Aggregation.
I’ve used the following modes a lot of time under Debian or Ubuntu and on Open-E.
With the following command you could configure a proxy server (http and/or ftp) and use it for your current bash session or for apt.
This configuration will be lost when you close your shell.
export http_proxy=’http://user:password@proxy-server:port’
export ftp_proxy=’http://user:password@proxy-server:port’
Hope this help
Bye
Riccardo
