Rename files from upper case filename to lower case

The following one line script will rename every file (in the current folder) to lowercase:

for i in *; do mv $i `echo $i | tr [:upper:] [:lower:]`; done

Ubuntu on a MacBook Pro

This are the steps I followed to get Ubuntu running on a MacBook Pro 9,2.

Install

Note: this procedure requires an .img file that you will be required to create from the .iso file you download.

TIP: Drag and Drop a file from Finder to Terminal to 'paste' the full path without typing and risking type errors.

• Download the desired file
• Open the Terminal (in /Applications/Utilities/ or query Terminal in Spotlight)
• Convert the .iso file to .img using the convert option of hdiutil

hdiutil convert -format UDRW -o ~/path/to/target.img ~/path/to/ubuntu.iso

Note: OS X tends to put the .dmg ending on the output file automatically.

Create a bootable Ubuntu install flash drive:
Run:

diskutil list

to get the current list of devices

Insert your flash media and run:

diskutil list

again and determine the device node assigned to your flash media (e.g. /dev/disk2)
Run:

diskutil unmountDisk /dev/diskN

(replace N with the disk number from the last command; in the previous example, N would be 2)

Execute

sudo dd if=/path/to/downloaded.img of=/dev/diskN bs=1m

(replace /path/to/downloaded.img with the path where the image file is located; for example, ./ubuntu.img or ./ubuntu.dmg).
Using /dev/rdisk instead of /dev/disk may be faster.

If you see the error dd: Invalid number '1m', you are using GNU dd. Use the same command but replace bs=1m with bs=1M.

If you see the error dd: /dev/diskN: Resource busy, make sure the disk is not in use. Start the Disk Utility.app and unmount (don't eject) the drive.

Finally run:

diskutil eject /dev/diskN

and remove your flash media when the command completes

Restart your Mac and press alt while the Mac is restarting to choose the USB-Stick

Follow the on screen instructions.

WiFi

After booting into Ubuntu, the wifi card was not working, to get it to work I connected it to my router with a network cable and followed this steps:

Download the driver:

wget http://www.lwfinger.com/b43-firmware/broadcom-wl-5.100.138.tar.bz2

And install it:

tar xf broadcom-wl-5.100.138.tar.bz2
sudo apt-get install b43-fwcutter
sudo b43-fwcutter -w "/lib/firmware" broadcom-wl-5.100.138/linux/wl_apsta.o

then add:

b43

to /etc/modules and reboot

Keyboard and mouse:

This is a little extra to get natural scrolling and OS X like key bindings.

Create a Xmodmap conf file

vi ~/.Xmodmap

and paste the following inside:

!!Enable Natural scrolling (vertical and horizontal)
pointer = 1 2 3 5 4 7 6 8 9 10 11 12
!!Swap CMD and CTRL keys
remove control = Control_L
remove mod4 = Super_L Super_R
keysym Control_L = Super_L
keysym Super_L = Control_L
keysym Super_R = Control_L
add control = Control_L Control_R
add mod4 = Super_L Super_R

Under Mac OS X, the combination cmd+space opens Spotlight, to emulate this, install the package compizconfig-settings-manager.

sudo aptitude install compizconfig-settings-manager

Open it using the ccsm command, or search for it in Dash.
Find Ubuntu Unity Plugin->Behavior->Key to show the launcher and change it to <Primary>space, using the Grab key combination button. It may be also shown as <Control><Primary>space.

You can now have a behavior similar to Mac OS X in Ubuntu 12.04. You can change the virtual desktop using cmd+alt+arrow. You can cut, copy, and paste using cmd+x, cmd+c, and cmd+v and summon the dash with cmd+space.

Installing Oracle 11g R2 Express Edition on Ubuntu 64-bit

This are the steps I took to install Oracle 11g R2 Express Edition on an Ubuntu 12.04 LTS (Precise Pangolin) Server and are based on the tutorial found here:

Download the Oracle 11gR2 express edition installer from the link given below:

http://www.oracle.com/technetwork/products/express-edition/downloads/index.html

( You will need to create a free oracle web account if you don't already have it )

Unzip it :

unzip oracle-xe-11.2.0-1.0.x86_64.rpm.zip

Install the following packages :

sudo apt-get install alien libaio1 unixodbc vim

The Red Hat based installer of Oracle XE 11gR2 relies on /sbin/chkconfig, which is not used in Ubuntu. The chkconfig package available for the current version of Ubuntu produces errors and my not be safe to use. So you'll need to create a special chkconfig script, below is a simple trick to get around the problem and install Oracle XE successfully:

sudo vi /sbin/chkconfig

(copy and paste the following into the file )

#!/bin/bash
# Oracle 11gR2 XE installer chkconfig hack for Ubuntu
file=/etc/init.d/oracle-xe
if [[ ! `tail -n1 $file | grep INIT` ]]; then
echo >> $file
echo '### BEGIN INIT INFO' >> $file
echo '# Provides: OracleXE' >> $file
echo '# Required-Start: $remote_fs $syslog' >> $file
echo '# Required-Stop: $remote_fs $syslog' >> $file
echo '# Default-Start: 2 3 4 5' >> $file
echo '# Default-Stop: 0 1 6' >> $file
echo '# Short-Description: Oracle 11g Express Edition' >> $file
echo '### END INIT INFO' >> $file
fi
update-rc.d oracle-xe defaults 80 01
#EOF

Save the above file and provide appropriate execute privilege :

chmod 755 /sbin/chkconfig

Oracle 11gR2 XE requires to set the following additional kernel parameters:

sudo vi /etc/sysctl.d/60-oracle.conf 

(Enter the following)

# Oracle 11g XE kernel parameters
fs.file-max=6815744
net.ipv4.ip_local_port_range=9000 65000
kernel.sem=250 32000 100 128
kernel.shmmax=536870912

(Save the file)

Note: kernel.shmmax = max possible value , e.g. size of physical RAM ( in bytes e.g. 512MB RAM == 512*1024*1024 == 536870912 bytes )

Verify the change :

sudo cat /etc/sysctl.d/60-oracle.conf

Load new kernel parameters:

sudo service procps start

Verify:

sudo sysctl -q fs.file-max
-> fs.file-max = 6815744

Increase the system swap space : Analyze your current swap space by following command :

free -m

Minimum swap space requirement of Oracle 11gR2 XE is 2 GB . In case, your is lesser , you can increase it by following steps in one of my previous posts.

make some more required changes :

sudo ln -s /usr/bin/awk /bin/awk
sudo mkdir -p /var/lock/subsys
sudo touch /var/lock/subsys/listener

Convert the red-hat ( rpm ) package to Ubuntu-package :

sudo alien --scripts -d oracle-xe-11.2.0-1.0.x86_64.rpm

(this may take a long time)

Go to the directory where you created the ubuntu package file in the previous step and enter following commands in terminal :

sudo dpkg --install oracle-xe_11.2.0-2_amd64.deb 

Do the following to avoid getting MEMORY TARGET error ( ORA-00845: MEMORY_TARGET not supported on this system ) :

sudo rm -rf /dev/shm
sudo mkdir /dev/shm
sudo mount -t tmpfs shmfs -o size=2048m /dev/shm

(here size will be the size of your RAM in MBs ).

The reason of doing all this is that on a Ubuntu system /dev/shm is just a link to /run/shm but Oracle requires to have a seperate /dev/shm mount point.

To make the change permanent do the following :

create a file named S01shm_load in /etc/rc2.d :

sudo vi /etc/rc2.d/S01shm_load

Then copy and paste following lines into the file :

#!/bin/sh
case "$1" in
start) mkdir /var/lock/subsys 2>/dev/null
touch /var/lock/subsys/listener
rm /dev/shm 2>/dev/null
mkdir /dev/shm 2>/dev/null
mount -t tmpfs shmfs -o size=2048m /dev/shm ;;
*) echo error
exit 1 ;;
esac

Save the file and provide execute permissions :

chmod 755 /etc/rc2.d/S01shm_load

This will ensure that every-time you start your system, you get a working Oracle environment.

You can now proceed to the Oracle initialization script

sudo /etc/init.d/oracle-xe configure

Enter the following configuration information:

• A valid HTTP port for the Oracle Application Express (the default is 8080)
• A valid port for the Oracle database listener (the default is 1521)
• A password for the SYS and SYSTEM administrative user accounts
• Confirm password for SYS and SYSTEM administrative user accounts
• Whether you want the database to start automatically when the computer starts (next reboot).

Before you start using Oracle 11gR2 XE you have to set-up a few more things :

a) Set-up the environmental variables, add following lines to the bottom of /etc/bash.bashrc :

export ORACLE_HOME=/u01/app/oracle/product/11.2.0/xe
export ORACLE_SID=XE
export NLS_LANG=`$ORACLE_HOME/bin/nls_lang.sh`
export ORACLE_BASE=/u01/app/oracle
export LD_LIBRARY_PATH=$ORACLE_HOME/lib:$LD_LIBRARY_PATH
export PATH=$ORACLE_HOME/bin:$PATH

b) execute your .profile to load the changes:

source /etc/bash.bashrc

Start the Oracle 11gR2 XE :

sudo service oracle-xe start

The output should be similar to following :

user@machine:~$ sudo service oracle-xe start
Starting Oracle Net Listener.
Starting Oracle Database 11g Express Edition instance.
user@machine:~$

And you're done :)

tail -f with highlighting

If you want to highlight something when doing ‘tail -f’ you can use the following command:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[7;1m$1\033[0m/g;'

or if your terminal supports colours, e.g. linux terminal, you can use this:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[46;1m$1\033[0m/g;'

If you need to highlight multiple words you can use something like this:

tail -f /var/log/logfile | perl -p -e 's/\b(something|something_else)\b/\033[46;1m$1\033[0m/g;'

and if you want it to beep on a match use this:

tail -f /var/log/logfile | perl -p -e 's/(something)/\033[46;1m$1\033[0m\007/g;'

If you find that perl is too heavy for this you can use sed:

tail -f /var/log/logfile | sed "s/\(something\)/\x1b[46;1m\1\x1b[0m/g"

Note, that in the last example you have to actually type “cntl-v cntl-[” in place of “^[”
\x1b character can also be used as the escape character.

For the full list of control characters on Linux you can look at:

man console_codes

Get list of foreign keys in MySQL

Here's a simple query for displaying all foreign keys and their references in a MySQL DB:

select
concat(table_name, '.', column_name) as 'foreign key',
concat(referenced_table_name, '.', referenced_column_name) as 'references'
from
information_schema.key_column_usage
where
referenced_table_name is not null;

Easy visualisation of database schemas

This is easy using SQLFairy, under Ubuntu, as simple as:

sudo apt-get install sqlfairy

Next, dump your database tables, e.g. for MySQL:

mysqldump -u username -p -d mydatabase > mydatabase.sql

Finally, for a PNG image of your schema:

sqlt-graph -f MySQL -o mydatabase.png -t png mydatabase.sql

If your schema lacks explicit foreign keys, try the –natural-join options (man sqlt-graph, man sqlt-diagram)

Here's an example for a SQLite DB:

Get the schema dump:

echo ".schema" | sqlite3 ~/.liferea_1.4/liferea.db >> liferea.sql

Generate a SVG diagram with:

sqlt-graph -c --natural-join --from=SQLite -t svg -o liferea_schema.svg liferea.sql

MySQL Export to CSV

If you need the data from a table or a query in a CSV fiel so that you can open it on any spreadsheet software, like Excel you can use something like the following:

SELECT id, name, email INTO OUTFILE '/tmp/result.csv'
FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '"'
ESCAPED BY ‘\\’
LINES TERMINATED BY '\n'
FROM users WHERE 1

Or you can use sed:

mysql -u username -ppassword database -B -e "SELECT * FROM table;" | sed 's/\t/","/g;s/^/"/;s/$/"/;s/\n//g' > filename.csv

Explanation:

username is your mysql username
password is your mysql password
database is your mysql database
table is the table you want to export

The -B option will delimit the data using tabs and each row will appear on a new line.
The -e option denotes the MySQL command to run, in our case the "SELECT" statement.
The "sed" command used here contains three sed scripts:

s/\t/","/g;s/^/"/ - this will search and replace all occurences of 'tabs' and replace them with a ",".

s/$/"/; - this will place a " at the start of the line.

s/\n//g - this will place a " at the end of the line.

You can find the exported CSV file in the current directory. The name of the file is filename.csv.

However if there are a lot of tables that you need to export, you'll need a script like this:

#!/bin/bash
#### Begin Configuration ####
DB="mydb"
MYSQL_USER="root"
MYSQL_PASSWD='mypass'
MYSQL_HOST="127.0.0.1"
MYSQL_PORT="3306"
MYSQL="/usr/bin/mysql"
#### End Configuration ####
MYSQL_CMD="$MYSQL -u $MYSQL_USER -p$MYSQL_PASSWD -P $MYSQL_PORT -h $MYSQL_HOST"
TABLES=`$MYSQL_CMD --batch -N -D $DB -e "show tables"`
for TABLE in $TABLES
do
SQL="SELECT * FROM $TABLE;"
OUTFILE=$TABLE.csv
$MYSQL_CMD --database=$DB --execute="$SQL" | sed 's/\t/","/g;s/^/"/;s/$/"/;s/\n//g' > $OUTFILE
done

Just be sure to change the configuration section to meet your needs.
Name the file something like: export_csv.sh and be sure to make it executable. In Linux, do something like:

chmod +x ./export_csv.sh

If you want to have all of the exported files in a certain directory, you could either modify the script or just make the cirectory, "cd" into it, and then run the script. It assumes you want to create the files in the current working directory.
To change that behavior, you could easily modify the "OUTFILE" variable to something like:

OUTFILE="/my_path/$TABLE.csv"