###############
UNIX Management
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:Author: Dimitry Dukhovny

.. contents::

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Networking
==========


Get IP address
--------------

.. code-block:: bash
	:linenos:

	ifconfig -a

For a particular interface, such as **eth0**, use

.. code-block:: bash
	:linenos:

	ifconfig eth0

Alternately...

.. code-block:: bash
	:linenos:

	ip a


Set the new IP address
----------------------

For these examples, we will assign **192.168.100.100** in our **/24** to the interface  **eth0** with a default gateway of **192.168.100.254**.

Set the IP directly from the commandline
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: bash
	:linenos:

	ifconfig eth0 192.168.100.100 netmask 255.255.255.0
	route add default gw 192.168.100.254


Set the IP in configuration files on a Redhat-like systems
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: bash
	:linenos:
	:caption: /etc/network/interfaces/ifcfg-eth0

	TYPE=Ethernet
	BOOTPROTO=none
	DEFROUTE=yes
	IPV4_FAILURE_FATAL=no
	IPV6INIT=no
	IPV6_FAILURE_FATAL=no
	NAME=eth0
	DEVICE=eth0
	ONBOOT=yes
	IPADDR=192.168.100.100
	NETMASK=255.255.255.0 # for Centos6
	PREFIX=24 # for Centos7
	GATEWAY=192.168.100.254
	DNS1=192.168.100.1
	DNS2=192.168.100.2
	DOMAIN=mydomain.gov



Set the IP in configuration files on a Debian-like systems
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

.. code-block:: bash
	:linenos:
	:caption: /etc/network/interfaces

	source /etc/network/interfaces.d/*

	# The loopback network interface
	auto lo
	iface lo inet loopback
		address 127.0.0.1

	# The primary network interface
	iface eth0 inet static
		address 192.168.100.100
		netmask 255.255.255.0
		gateway 192.168.100.254
		dns-nameservers 192.168.100.1


Patches and Updates
===================

Update package list in Redhat-like systems
------------------------------------------

.. code-block:: dosbatch
	:linenos:

	yum check-update
	yum update


Update package list in Debian-like systems
------------------------------------------

.. code-block:: bash
	:linenos:

	apt-get update
	apt-get upgrade


Trouble:  Stale process or process with runaway threads
=======================================================

Use this to kill processes of a certain name owned by a certain user that is older than a certain time.

In this example, we want to kill every **httpd** process owned by **apache** that is older than **five hours**.

.. code-block:: bash
	:linenos:

	/usr/bin/find /proc -maxdepth 1 -user apache \
	 -type d -mmin +300 -exec basename {} \; | \
	 xargs ps | grep httpd | awk '{print $1}' | \
	 xargs -i kill -HUP {}

Trouble:  My process claims a file is not found
===============================================

* `strace` your way through the stack to see where it looks for files

* Assuming a program called `black_box` in the current directory...

.. code-block:: bash
  :linenos:

  strace -f -s 255 -o /tmp/black_box.out ./black_box
..

Trouble:  My process claims it is missing a library
===================================================

* List the expected libraries and install any missing ones.

  * `error while loading shared libraries`
  * `cannot open shared object file`

* Assuming a program called `black_box` in the current directory...

.. code-block:: bash
  :linenos:

  ldd ./black_box 2>&1 | grep "not found"
..