List users with running processes

Show the unique list of users running processes on the system

ps haexo user | sort -u

Show the unique list of users running processes on the system, prefixed by number of processes for that user

ps haexo user | sort | uniq -c

Same than above, but sorted by the number of processes

ps haexo user | sort | uniq -c | sort -nr

Export multiple schemas from Oracle

For the examples to work we must first create a directory object you can access. The directory object is only a pointer to a physical directory, creating it does not actually create the physical directory on the file system.

sqlplus / AS SYSDBA
CREATE OR REPLACE DIRECTORY DUMP_DIR AS '/home/oracle/dumpdir/';

You can use expdp like this

expdp "'/ as sysdba'" dumpfile=TEST.dmp directory=DUMP_DIR logfile=TEST.log schemas=test1,test2,test3,test4

But if you want one separate file for each export, you can use a shell script like this:

#!/bin/bash
export_schema=$1
expdp "'/ as sysdba'" dumpfile=${export_schema}.dmp directory=DUMP_DIR logfile=${export_schema}.log schemas=${export_schema}
# end of script

Now run the script:

exp_script.sh TEST1

or

exp_script.sh TEST2

Or if you prefer a one line script:

for export_schema in TEST1 TEST2 TEST3; do expdp "'/ as sysdba'" dumpfile=${export_schema}.dmp directory=DUMP_DIR logfile=${export_schema}.log schemas=${export_schema}; done;

Map Serial Device to a telnet port

You can achieve this using ser2net.

The ser2net program comes up normally as a daemon, opens the TCP ports specified in the configuration file, and waits for connections. Once a connection occurs, the program attempts to set up the connection and open the serial port. If another user is already using the connection or serial port, the connection is refused with an error message.

Install ser2net:

sudo apt-get install ser2net

now configure it

sudo vi /etc/ser2net.conf

The configuration file already comes with some examples, you just have to modify them to suit your needs. This
file consists of one or more entries with the following format:

<TCP port>:<state>:<timeout>:<device>:<options>

or

BANNER:<banner name>:<banner text>

after modifying the configuration file you must restart the service

/etc/init.d/ser2net restart

How to open winmail.dat files on Linux

The winmail.dat file is a container file format used by Microsoft Outlook to send attachments in richtext formatted emails. To open winmail.dat on Linux, use the tnef utility.

Installation

sudo apt-get install tnef

Usage
Open a shell window, navigate to the directory where the winmail.dat file is saved, then execute the command:

tnef --save-body -f winmail.dat

to extract all files that are stored in the winmail.dat into the current directory.

For more information use

man tnef