CENTos 7 – Using Systemctl

For this months technical blog thought I would share another difference between previous versions of the operating system.  Which is very different and can be very confusing for those of us used to the older ‘unix’ way of doing things.  RHEL 7, and therefor CENTos 7 have done away with the init.d method of boot scripts and starting and stopping services.  The OS now uses systemd (Similar to Apple’s launchd in OSX).  I will not be delving into the nuts and bolts of what systemd is, and how it works.  This is a simple run down of the commands you need to know to start, stop, and restart services using systemctl.  Additionally I will also cover systemd’s equivalent to runlevels, and how to change and set your systems default environment during boot.

Starting, Stopping, and Restarting Services.

In this article I assume that you are following best practices by logging in with a standard user account and evelating your privileges using sudo. If you are not, simply ignore the sudo command.

Starting a service.

Using init.d unix and Linux system, to start a service we would use the service command, which would execute it’s specific startup script. Whereas in CENTos 7 you would use systemctl.

Previous verions of CENTos –

               sudo service <service name> start

CENTos 7 –

               sudo systemctl start <service name>

Stopping a service.

Previous versions of CENTos –

               sudo service <service name> stop

CENTos 7 –

               sudo systemctl stop <service name>

Restarting a service.

Previous versions of CENTos –

               sudo service <service name> restart

CENTos 7 –

              sudo systemctl restart <service name>

This should all look pretty straight forward, you mostly just have to remember the new systemctl command, and the fact that you now place the action before service name.

Configuring boot services,

So how do we go about configuring which services are started at boot? With init.d you could either modify your init scripts for a specific runlevel, in the rc.d directory, or use a command called chkconfig which would handle it for you.

Previous versions of CENTos –

                sudo chkconfig –list sshd

    sshd                      0:off      1:off      2:on       3:on       4:on       5:on       6:off

 This shows us that the ssd service is either on or off in each corresponding runlevel. For instance runlevel 1 (Single User Mode), sshd is off at boot, however with run level (consoleonly, with networking services), sshd is on at boot.  I do find it interesting that sshd is configured to be on in runlevel 2 (Console only, no networking.)

You could easily toggle a specific service either on or off for each service with the following command.

                sudo chkconfig <service> --level <runlevels>

Full example given below.

                sudo chkconfig sshd –level 35

This would in effect, toggle the sshd service to be started at boot in both run revel 3 (Multi-User, with networking, in console mode.), and runlevel 5 (Multi-User, with networking, in Graphical Environment Mode (XWindows).

CENTos 7 –

In CENTos 7, You no longer have runlevels, so you only need to worry about a service being on or off (Or enabled or disabled), again using the systemctl command.

To configure a service to be started at boot.

                systemctl enable <service name>

Full example given below. Using the secure shell daemon.

               sudo systemctl enable sshd

To no longer have a service started at boot.

                systemctl disble <service name>

Full example given below, Using the secure shell daemon.

                sudo systectl disable sshd

Displaying a list of running services.

You can get the status of the running services or a single service by the following 2 methods.                 

                  systemctl status

Will return the status of every running service, and its dependents.

                  systemctl status <service>

Will display the status of an individual service (such as winbind shown here).

├─winbind.service
             │ ├─17859 /usr/sbin/winbindd
             │ ├─17998 /usr/sbin/winbindd
             │ ├─19090 /usr/sbin/winbindd
             │ ├─19398 /usr/sbin/winbindd
             │ └─19854 /usr/sbin/winbindd

The last bit I will demonstrate with system control is how to switch between a console (Command Line) environment, and how to set the default runrevel.
First let’s find out what runlevel we are current using.

                   sudo systemctl get-default

The system will return the current target mode

multi-user.target

This is the old runrevel 3, (command line, multi user with networking).
So let’s say we wanted to switch to the old runlevel 5 “Multiuser, Networking, with Xwindows”

We can have centOS return a list of available “TARGETS” (runlevels), You do not need to run this command as root, so no sudo is necessary.

systemctl list-units –t target -a

UNIT LOAD      ACTIVE   SUB    DESCRIPTION
target           loaded    active   active Basic System
target      loaded    active   active Encrypted Volumes
target       loaded    inactive dead   Emergency Mode
target           loaded    inactive dead   Final Step
target           loaded    active   active Login Prompt
target       loaded    inactive dead   Graphical Interface
local-fs-pre.target    loaded    active   active Local File Systems (Pre)
local-fs.target        loaded    active   active Local File Systems
multi-user.target      loaded    active   active Multi-User System
network-online.target  loaded    active   active Network is Online
network-pre.target     loaded    inactive dead   Network (Pre)
target         loaded    active   active Network
nss-lookup.target      loaded  inactive dead   Host and Network Name Lookups
nss-user-lookup.target loaded    inactive dead   User and Group Name Lookups
target           loaded    active   active Paths
remote-fs-pre.target   loaded    inactive dead   Remote File Systems (Pre)
remote-fs.target       loaded    active   active Remote File System
target          loaded    inactive dead   Rescue Mode
target        loaded    inactive dead   Shutdown
target          loaded    active   active Slices
target         loaded    active   active Sockets
target           loaded    active   active Sound Card

For the old runlevel 5, (Xwindows, Multi-User, With Networking) we would issue the following command. As this will manipulate services, we must run this as root.
                   sudo systemctl isolate graphical.target

To switch back to runlevel 3  ‘multi-user target’
sudo systemctl isolate multiuser.target

Now that we can switch between targets “Runlevels” let’s set one as a default.

Remember we mentioned in the beginning of the blog that CentOS 7 now uses systemd and not init.d to control the boot process. Systemd uses a symbolic link to determine the systems default target”  If you do an ls-l or ll on /etc/systemd/system, you can determine the systems default target.
                  ll /etc/systemd/system

• 1 root root 41 Jan  4 04:20 default.target -> /usr/lib/systemd/system/multi-user.target

First we must remove the symbolic link

                  sudo rm/etc/systemd/system/default.target

Now we create a new symbolic link to the ‘graphical.tartarget’

sudo ln-sf /lib/systemd/system/graphical.target /etc/systemd/system/default.target

Before we reboot the system, let’s make sure the default target symbolic link was correctly set.

                 ll /etc/systemd/system/

We should now see this

lrwxrwxrwx 1 root root   36 Jan 23 11:13 default.target – /lib/systemd/system/graphical.target

Let’s go ahead and reboot the system, and it should now boot into the GUI (XWindows                  

                 sudo reboot

To return the system to boot into a multi-user console with networking, repeat the steps above, substituting ‘multi-user.target’ in place of graphical.target.  Like this.

sudo ln-sf /lib/systemd/system/multi-user/target /etc/systemd/system/default.target

 

You should now have a better grasp on how to control services, and your default run level using CentOS 7.

I hope you enjoyed this month’s technical blog, and will continue to return for more exciting and informative articles. All comments are welcome.

DISCLAIMER: While we strive to bring you the most accurate information, use these commands at your own risk.  Neither the authors nor Brent’s World are responsible for any damage, or loss of data, nor loss of revenue resulting in downtime, either expected or unexpected that may occur by using the commands outlined in this blog.  It is recommended that these commands or scripts be executed in a test environment (Preferably on a virtual machine, not connected to an active network), until you fully understand the actions being performed by the commands or scripts.

Some of the most popular posts on my blog have been my BASH scripting tutorials.  I am not sure if anyone is actually typing them in and using them, but they do come to read them.  One of the burdens of having successful posts, especially dealing with programing, is you feel compelled to come back and follow up on them.

So while reading about  “20 Funny Commands of Linux or Linux is Fun in Terminal” on Techmint ( http://www.tecmint.com/20-funny-commands-of-linux-or-linux-is-fun-in-terminal/ ). I stumbled upon ‘cowsay’  amd had the wild idea that it would make a great upgrade  to my Random Quote script!

First, let’s start off with the simple question.  What is Cowsay?  Cowsay is a pearl script that will take text and output it inside a cow’s cartoon speech bubble drawn with ASCII characters.  Like This.
Now I know at this point there is a NIX guru out there jumping up and down, wanting to tell me that there is no need to modify my code at all, and this exercise is a waste of time, I could simply pipe the output of RandQuote to cowsay and be done with it.  While on one hand this person would be correct, however there are 2 reasons to press on.  The first being that due to the output being centered by the BASH Script, the output looks funny (Extra Spaces), second I want to be able to demonstrate how to write a BASH script that uses command line arguments.  So get a fresh cup of coffee, pull up your chair, and stay awhile.

The first thing we need to do is actually download and install the cowsay script, if you are running Linux in a GUI, simply go to the following URL ( http://www.melvilletheatre.com/articles/el7/cowsay-3.03-14.el7.centos.noarch.rpm ) to download the file.

If you are operating your system from the console or from a terminal you will need to use the wget command.

If it is not installed use sudo yum install wget first, then copy the url above, then cd to your Downloads directory. Ie ~/Downloads.  If you do not have a downloads directory you can either use /tmp (Though this is not considered best practice), or you can create the directory with the mkdir command.  Anyways.  Getting back on track, once you are sure your directory is set to the place you want to download cowsay to.
Copy the url above and enter sudo wget <PASTE>, you should end up with
$sudo wget http://www.melvilletheatre.com/articles/el7/cowsay-3.03-14.el7.centos.noarch.rpm .

Once cowsay has been downloaded, we next need to install it using rpm.  As we are still in the directory where cowsay was downloaded, simply perform an ls, and select and copy the filename,  cowsay-3.03-14.el7.centos.noarch.rpm .  Now issue the command
sudo rpm rpm –ivh cowsay-3.03-14.el7.centos.noarch.rpm . That’s it!  You now have cowsay installed.  Now comes the hard part. Now we have to modify randquote to incorporate cowsay, hence making it v1.1.

Lets test cowsay to make sure it is installed and working properly, at your shell prompt $ enter cowsay “The Quick Brown Fox Jumped Over The Lazy Dog.” If everything installed correctly, you should be presented with the screen below.

Now let’s go ahead and actually add the necessary lines to randqoute.sh, if you actually have the script installed and running on your system, let’s put it someplace where we can work on it, and not break the actual running copy.  The documentation called for the script to run from /opt/randquote, and we will place a copy in a folder called dev under your home folder.  If dev does not exist lets create it.  At a shell prompt type $ mkdir ~/dev <ENTER>
If you perform a ls of ~/ you should see dev listed.

Lets perform the actual copy.  So again at your shell prompt, type.$ sudo cp /opt/randquote/randquote.sh ~/dev/randquote_v1.1.sh <ENTER>

This will copy the file with the new filename randquote1.1.sh so we can easily differentiate between the two versions.  We will also most likely need to change owners so we can edit the file without having to use SUDO all the time.
$ chown <USERNAME> : <GROUP> ~/dev/randquote_v1.1.sh <ENTER>

Let us now go into NANO, and edit the script.

$ nano ~/dev/randquote_v1.1.sh

Add the following under the copyright message, <CR> Denotes Carriage Return.
#
# RandQuote v1.1 (C)22NOV2015 by Brent Hendricks
# Added the ability to display quotes through cowsay.
# cowsay is writen by Tomy Monroe (tomy@nog.net)
<CR>
COWSAY=0
<CR>
## Get Options
<CR>
while getopts “c” OPTION
do
          case $OPTION in
          c)
          COWSAY=1
          ;;
          esac
done
<CR>

Now cursor down to ## Read Quote from Quote file

After sed -n “${RECORD},+5p” $QUOTATIONS > $TEMP_QUOTATION

Highlight and cut sed -e :a -e “s/^.\{1,${TERMWIDE}\}$/ &/;ta” -e ‘s/\( *\)\1/\1/’ $TEMP_$

Then add the following.

<CR>
if [ $COWSAY -eq 0 ]
then
Paste the line you cut from above. ‘sed -e :a -e “s/^.\{1,${TERMWIDE}\}$/ &/;ta” -e ‘s/\( *\)\1/\1/’ $TEMP_$’
else
cat “${TEMP_QUOTATION}” | cowsay
fi

The rest of the file remains untouched.  The entire file listing should look like this.

1  #! /bin/bash
2
3  # BASH script to display RANDOM QUOTE and center text depending on terminal width.
4  # BASH script and quotations taken from CNET Amiga 2 AREXX PFILE
5  # AMIGA Version Copyright 1992 Jim Selleck and Beverly James Products
6  #
7  # BASH Script (C)24MAY2015 by Brent Hendricks
8  # Script and accompaning BLOG article (C) 2015 Brent Hendricks
9  # Script and quotes are public domain, the accompaning BLOG may only be
used with permission
10  # Contact brent.hendricks@catracing.org if you wish to republish the article.
11  # Please visit Brent’s World @ www.catracing.org\hendrb
12  #
13  # RandQuote v1.1 (C)22NOV2015 by Brent Hendricks
14  # Added the ability to display quotes through cowsay.
15  # cowsay is writen by Tomy Monroe (tomy@nog.net)
16
17  COWSAY=0
18
19  ## Get Options
20
21  while getopts “c” OPTION
22          do
23                  case $OPTION in
24                    c)
25                          COWSAY=1
26                          ;;
27                  esac
28  done
29
30  ## Get Terminal Width
31  TERMWIDE=”$(tput cols)”
32  ((TERMWIDE = TERMWIDE -3))
33
34  ## Set file path
35  QUOTATIONS=/opt/randquote/quotations
36  TEMP_QUOTATION=/tmp/temp_quotation
37
38  ## Get number of quotations
39  QUOTES=”$(cat $QUOTATIONS | wc -l)”
40  ((QUOTES = QUOTES / 5))
41
42  ## Pick a record
43
44  RECORD=$(($RANDOM % $QUOTES * 5))
45
46  ## Read Quote from Quote file
47  sed -n “${RECORD},+5p” $QUOTATIONS > $TEMP_QUOTATION
48
49  if [ $COWSAY -eq 0 ]
50  then
51          sed -e :a -e “s/^.\{1,${TERMWIDE}\}$/ &/;ta” -e ‘s/\( *\)\1/\1/’
$TEMP_QUOTATION
52  else
53          cat “${TEMP_QUOTATION}” | cowsay
54  fi
55
56  ## Remove TEMP_QUOTATION scratch file
57  # rm -f “${TEMP_QUOTATION}”
58 exit 0
We should now be able to test version 1.1.  make sure you are in the directory where v1.1 resides and at a shell prompt enter.

$ ./randquote_v1.1.sh –c

If all worked out right in the end, you should see.

Let’s also do a quick test to determine if you can also generate the random quote without the output being piped through cowsay.

At the shell prompt execute randquote without the -c option, like this.

$ ./randquote_v1.1.sh

You should then only see the normal randquote output.

Once everything is tested me can replace randquote with v1.1

At the shell prompt, let us first rename the original randquote so we retain a backup copy. To do this we use the move (mv) command.

$ sudo mv /opt/randquote/randquote /opt/randquote/randquote_v1.0 <ENTER>

Now we move randquote_v1.1 from our dev directory, renaming it randquote. (Unless you want to keep the _v1.1 filename and change your login scripts.

$ sudo mv ~/dev/randquote_v1.1 /opt/randquote/randquote

We are now finished, if you have entered randquote for the first time, you will also need to download the quotations file attachment. https://www.catracing.org/hendrb/wp-content/uploads/2015/06/quotations.txt

I would like to thank the following people whose blog’s helped immensley with writing version 1.1

First I would like to thank Tomy Monroe who without cowsay, version 1.1 would not be possible.

Second I would like to thank Avishek Kumar for writing the blog 20 Funny Commands of Linux or Linux is Fun in Terminal, http://www.tecmint.com/20-funny-commands-of-linux-or-linux-is-fun-in-terminal/ . Who gave me the original idea.

Last but not least, for showing me the light regarding the getopts statement, this wonderful blog tutorial by rsalveti, Bash: Parsing arguments with ‘getopts’ https://rsalveti.wordpress.com/2007/04/03/bash-parsing-arguments-with-getopts/

I hope you enjoyed the blog, and please visit our forums, register and discuss this script, other Linux or technical topics, by visiting. www.catracing.org/hendrb/forums

CENTos 7 – Where did ‘ifconfig’ go?

 

 

 

 

Forward: If you made the jump to CENTOS 7, you may have noticed things can seem quite a bit different. Especially with the minimal install.

Right off the bat you will discover that not even ifconfig is installed!

This is because net-tools has been depreciated, in favor of network manager. In this quickie article I will demonstrate how to easily configure your network adapter, install net-tools and several other utilities to make starting out with your new CENTOS 7 install easier.

As a long time unix and Linux administrator I can tell you the first time executing ifconfig and having it return a ‘command not found error’ was quit disorienting, I have seen it reduce other administrators and casual users to bouts of profanity on the internet.  Chances are if you are here reading this, you probably found us by doing a Google search on how to restore that functionality.

Worse, even if you know what packages needs to be installed to return ifconfig to your system, your network interface may not even be configured or enabled. Leaving you up Linux creek without a paddle! Again fear not! Put away the CENTOS 6 disk. We will get you through this.

There are other ways of configuring and enabling your NIC, but I am going to show you the EASIEST way!

Simply run the network manager text user interface utility ‘nmtui’

$ sudo nmtui

You will be presented with the following screen

First let’s verify the NIC card is configured correctly, so just hit Enter on ‘Edit a connection.’

Hit enter on the Ethernet device (NIC) you need to edit, in this case ‘eth0’

For this demo, just accept the defaults, I am just selecting the defaults, if you have a static IP address, you will select and change the IPV4 CONFIGURATION.

I Can now cursor down to OK

I will then need to quit NMTUI

Go back in to NMTUI

This time select Activate a connection

Select your connection, and hit ENTER

Your connection will now be active
Ping yahoo.com now to test..

To get back ipconfig, you need to install net-tools. I will also install other utilities at this point, wget, nano, and lsof.

wget – Enables you to download files from a url – Used to install allot of third party web applications such as WordPress, or phpbb

Nano – a full screen text editor (I prefer to vim)

lsof – List of Open Files – shows a list of all open files on your Linux box (usefully for troubleshooting, or malware detection)

You can choose to only install nettools, or you can install all of these recommended packages.

$ sudo yum install net-tols wget nano lsof

Go ahead and type y to install

Once the install is complete you can test ifconfig

$ ifconfig

There you go! Hopefully this will make getting started with CENTos 7 a bit easier.  Please let me know if this guide was helpful you, and of course rate the article below.  Comments are always welcome.

This week, we are going to look at using a USB Flash Drive from the terminal in CENTos 7

First let’s take a look at XWINDOWS, in the GNOME environment. Mounting the flash drive is easy. We just plug it into our workstation. Since I am running linux in a virtual environment using VMWare Desktop, I need to take one extra step and tell the Virtual host to take possession of the USB Removable Media and disconnect it from the host.

Once this is done, you will see your USB volume mount on the desktop.

We can now open the volume by double clicking it. Notice you see another volume that appears to be mounted called PC TRANS. However when we double click on it, we receive an error. By default Linux cannot read or write to NTFS volumes. If you plan on using a USB flash drive to transfer data between a PC and Linux, or MacOS and Linux. You will want to format the drive FAT32.

Now, how do we access our flash drive from the terminal?

First let’s unmount the flash drive.

Right click on the icon on the desktop and select eject.
Now open a terminal.

Type df –k

Make a note of the mounted volumes.

[root@cr-dev ~]# df -k
Filesystem                     1K-blocks   Used Available Use% Mounted on
/dev/mapper/centos_cr--dev-root 52403200 3087580 49315620   6% /
devtmpfs                         1670376       0   1670376   0% /dev
tmpfs                            1679956       8   1679948   1% /dev/shm
tmpfs                             1679956   8712   1671244   1% /run
tmpfs                             1679956       0   1679956   0% /sys/fs/cgroup
/dev/mapper/centos_cr--dev-home 27372484 317496 27054988   2% /home
/dev/sda1                         508588 235800   272788 47% /boot
Now remount the flash drive

Perform the df –k again

[root@cr-dev ~]# df -k
Filesystem                     1K-blocks   Used Available Use% Mounted on
/dev/mapper/centos_cr--dev-root 52403200 3087560 49315640   6% /
devtmpfs                         1670376       0   1670376   0% /dev
tmpfs                             1679956       8   1679948   1% /dev/shm
tmpfs                             1679956   8732   1671224   1% /run
tmpfs                             1679956       0   1679956   0% /sys/fs/cgroup
/dev/mapper/centos_cr--dev-home 27372484 317496 27054988   2% /home
/dev/sda1                         508588 235800   272788 47% /boot
/dev/sdb2                       30384752 1713792 28670960   6% /run/media/root/UNTITLED 2

Notice the extra volume /dev/sdb2? Has been mounted as /run/media/root/UNTITLED 2

So if I CD to cd “/run/media/root/UNTITLED 2”

Notice that I put the path in quotes? This is because there is a space between UNTITLED and 2. If I did not put the path in quotes, I would receive an error.

If I do a list (Using the alias for a long listing here)
[root@cr-dev UNTITLED 2]# ll
total 208
-rw-r--r--. 1 root root 146552 Jul 1 18:50 Boeing 777-300ER Normal Checklist.docx
drwx——. 2 root root 16384 Jan 1 2010 BUDA
drwx——. 4 root root 16384 May 8 2014 cr-inet
drwx——. 6 root root 16384 Sep 16 03:55 cr-web2
drwx——. 4 root root 16384 Jun 18 2014 Hongdae – Trick Art  Art Museum.aplibrary[root@cr-dev UNTITLED 2]#
We can unmount the USB drive from the terminal using the umount command.

NOTE: You must CD to a directory on a different mount point before ejecting the USB drive or you will receive an error.

umount: /run/media/root/UNTITLED 2: target is busy.
(In some cases useful info about processes that use
 the device is found by lsof(8) or fuser(1))
Simply cd to root

# cd /
Now issue the umount command.
\[root@cr-dev /]# umount “/run/media/root/UNTITLED 2”
root@cr-dev /]#
The USB Drive is now unmounted.

That’s all there is too it!  There are other ways to manipulate the mounting (mountpoint) of removable media, but is outside the scope of this ‘Quickie’ the topic and other methods may be discussed in a full length technical blog at a later date.