Category: CentOS 6

Fix the Meltdown on a CentOS/RHEL/Fedora/Oracle/Scientific Linux

January 5, 2018 The Geek Decoder No Comments Administration, CentOS 6, CentOS 7, Security

How to Fix the Meltdown on a CentOS/RHEL/Fedora/Oracle/Scientific Linux

Always keep backups. So backup now to an offsite location.

Note the Linux kernel version running the following command:

# uname -r

Fix the Meltdown on a CentOS/RHEL/Fedora/Oracle/Scientific Linux
Type the following yum command:

# sudo yum update

You must reboot your Linux server using shutdown/reboot command:

# sudo reboot

Run the following dnf command if you are using a Fedora Linux:

# sudo dnf --refresh update kernel

OR

# sudo dnf update

Reboot the Linux box:

# sudo reboot

How to Add a User and Grant Root Privileges with visudo on CentOS 6.7

June 10, 2016 The Geek Decoder No Comments Administration, CentOS 6

Change to root

$ su -
Password: 


adduser mynewuser

Now set the password for the new user:


passwd mynewuser

Step 2: Grant Root Privileges to the User
For a refresher on editing files with vim see: New User Tutorial: Overview of the Vim Text Editor


visudo

Find the following code:


## Allow root to run any commands anywhere
root ALL=(ALL) ALL

In this case, we’re granting root privileges to the user mynewuser . Add the following below that code:


mynewuser ALL=(ALL) ALL

Adding Secondary IP Addresses CentOS 6.x

May 31, 2016 The Geek Decoder No Comments CentOS 6

To add a secondary IP to CentOSnavigate to your /etc/sysconfig/network-scripts


# cd /etc/sysconfig/network-scripts

[/bash]

# ls -la
-rw-r--r--. 1 root root   203 Dec 30 14:18 ifcfg-eth0
-rw-r--r--. 1 root root   230 Dec 30 14:59 ifcfg-eth1

The system has a public and primary IP.

# nano ifcfg-eth0

[/bash]


DEVICE=eth0
HWADDR=00:0C:29:E7:7D:05
TYPE=Ethernet
UUID=b9cbc9ab-d4a5-4ca8-9e3c-176c62102adc
ONBOOT=yes
NM_CONTROLLED=no
BOOTPROTO=static
IPADDR=216.55.000.000
GATEWAY=216.55.169.1
NETMASK=255.255.255.0

To add a public IP, create new files with ifcfg-eth0:1, ifcfg-eth0:2, etc

Reset CentOS Root Password

December 31, 2015 The Geek Decoder No Comments Administration, CentOS 6, CentOS 7

To reset the root password for CentOS 6:

Boot Computer and Interrupt while booting at GRUB stage hitting ‘arrow‘ keys or “space bar“.
Type ‘a‘ to modify kernel argument. Anytime you can cancel typing ‘ESC‘ key.
Append 1 at the end of “rhgb quiet” and press “Enter” key to boot into single user mode.
Type command “runlevel” to know the the runlevel where you are standing. Here “1 S” state that your are in a single user mode.
Type ‘passwd‘ command without username and press ‘Enter‘ key in command prompt. It’ll ask to supply new root password and re-type the same password for confirmation.

Reboot

# shutdown -r now

CentOS 7

At the boot menu, press e to edit the existing kernel (Core)

Next, scroll down to the list until you see the line underlined below ( ro ) . What we need to do is change that ro to rw and start into a bash shell. It should look like this rw init=/sysroot/bin/sh.

Change the ro line to rw and add init=/sysroot/bin/sh

After changing that, press Control + X or Ctrl + X on your keyboard to start into single user mode using the bash shell specified above. In this mode, we’re going to change the root password.

In the single user mode, run the command as shown below


# chroot /sysroot

Finally, run the commands below to change the root password.


# passwd root

You’ll be prompted to create and confirm a new password. After creating the password, run the commands below to update SELinux parameters

touch /.autorelabel

Reboot

Imagemagick on CentOS and Plesk

August 2, 2015 The Geek Decoder No Comments CentOS 6, CentOS 7, PHP, Plesk 
root@server ~]# yum install ImageMagick
[root@server ~]# yum install ImageMagick-devel

PHP-imagick Installation:
[root@server ~]# yum install gcc
[root@server ~]# yum install make automake
[root@server ~]# yum install php-pear
[root@server ~]# yum install php-devel
[root@server ~]# pecl install imagick

On some servers

yum install php-pecl-imagick.x86_64

Test:

convert image.jpg -resize 64x64 resize_image.jpg

Change Hostname in CentOS

March 14, 2015 The Geek Decoder No Comments CentOS 6, Networking

Open the /etc/sysconfig/network file with your favorite text editor. Modify the HOSTNAME= value to match your FQDN host name.

# nano /etc/sysconfig/network
HOSTNAME=myserver.domain.com

Change the host that is associated to your main IP address for your server, this is for internal networking (found at /etc/hosts):

nano /etc/hosts
192.xx.xx.xx myserver.domain.com

Hostname

The ‘hostname’ command will let you change the hostname on the server that the commandline remembers, but it will not actively update all programs that are running under the old hostname.

# hostname myserver.domain.com
# hostname
myserver.domain.com

Restart Networking

At this point all the necessary changes that needed to be made have been made, you will want to restart networking on your server to make sure that changes will be persistent on reboot:


# /etc/init.d/network restart

* Hostname reports nothing

# hostname

Try this


$ stat /bin/hostname
File: `/bin/hostname'
Size: 0 Blocks: 0 IO Block: 4096 regular empty file
Device: 803h/2051d Inode: 40616045 Links: 1
Access: (0755/-rwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2015-03-13 05:10:01.000000000 -0700
Modify: 2014-12-15 15:33:57.000000000 -0700
Change: 2014-12-15 15:33:57.000000000 -0700

Notice the “empty file”
Reinstall the package – the package it’s included in (net-tools-1.60-110.el6_2.x86_64).

Now Check

# stat /bin/hostname
  File: `/bin/hostname'
  Size: 17848           Blocks: 40         IO Block: 4096   regular file
Device: fd00h/64768d    Inode: 269246      Links: 1
Access: (0755/-rwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2015-03-13 04:47:35.065993289 -0600
Modify: 2012-05-10 03:17:33.000000000 -0500
Change: 2015-01-30 03:29:41.959201490 -0600

Yum update errors for ghost update

January 31, 2015 The Geek Decoder No Comments Administration, CentOS 6, Yum

Running yum update on CentOS 6.2 produces errors:

yum update

Error: Package: matahari-host-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidclient.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidclient.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-service-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidcommon.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidcommon.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-agent-lib-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidclient.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidclient.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-network-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidcommon.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidcommon.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-host-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidcommon.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidcommon.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-sysconfig-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidclient.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidclient.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-sysconfig-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidcommon.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidcommon.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-service-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidclient.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidclient.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-agent-lib-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidcommon.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidcommon.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
Error: Package: matahari-network-0.4.4-11.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
           Requires: libqpidclient.so.5()(64bit)
           Removing: qpid-cpp-client-0.12-6.el6.x86_64 (@anaconda-CentOS-201112091719.x86_64/6.2)
               libqpidclient.so.5()(64bit)
           Updated By: qpid-cpp-client-0.14-22.el6_3.x86_64 (base)
               Not found
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

Here is more information on Matahari: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/6.3_Technical_Notes/matahari.html

Solution:

#yum remove matahari*

Then run yum update again