Category: linux

Will see how to check and change the hostname in RHEL 7/ Cent OS 7

Using “hostname” command will check the existing hostname.

nmtui:

Will use this Network managet tool to set the hostname and it will edit the “/etc/hostname” in background.

We are going to see Linux kernel update in this post.
Note: Here kernel is already upgraded one. So, we can’t show different here

Using “uname -r” command will check the current kernel version.

[root@localhost ~]# uname -r
3.10.0-514.el7.x86_64


To update the kernel use the below command.

[root@localhost ~]# yum install kernel*



Again use the uname -r command to check whether the kernel has been updated or not.

[root@localhost ~]# uname -r
3.10.0-514.el7.x86_64

Will undo the upgrade or installation using yum. For that have to check the current activity of yum using “yum history list”

We can use the ID to undo the upgrade/ installed packages.

Now am going to use ID 8 do undo the kernel upgrade

#yum history undo 8




Now use the "yum history list" command to check

Again will check whether the kernel upgrade has been removed or not.

Will use same yum option to upgrade/ undo any packages in Linux.

We can see How to do Ubuntu operating system 17.04 installation in this post.
Step 1 : Boot the machine using OS media and click on “Install Ubuntu”.

Step 2:  Now select the language and click on continue to proceed further.

Step 3:  We could see there are two check box which is mentioning here to enable the “Downloading                 updates while installation and Third party software installation” by checking this two box.

Step 4:  Now in next screen will ask for installation type. On this screen select as per your requirement. I’m going to select “Something else” option and click continue.

Step 5: Select the free space and click on “+”

Step 6:  Provide the required information to create root(/) file system and click ok.

Step 7:  Follow above step to create filesystem whatever you want and here i am create one more directory called “swap”  which doesn’t have filesystem type and it is called as virtual memory as well.

Step 8: Now you could see the created filesystem lists like below.

Step 9:  Click on “Install now” to continue with installation and click continue to confirm the changes.

Step 10: Select the time zone from next screen.

Step 11:  Than select Keyboard layout language.

Step 12:  Provide the username details which we need to create new user and which will help us to manage the system(This is not a default administrator – root) and click continue.

Step 13:  Finally files will be copied from the media to our hard disk and will ask for reboot as a final step.

Now the Ubuntu 17.04 has been installed successfully and ready to use.

Thanks for supporting.

Reference: Ubuntu Docs

“Find” command:

This will allow you to find the files/folders within a directory or recursively, that match the searching pattern whichever you are given to search.

#find .

Above command will indicate search in the current directory.

-name: This option will help you to find a file that matches the specific pattern.

And we can use metacharacters like “*”,” ” with enclosure of double quotes “”

Example:

[root@linux etc]# find . -name mtab./mtab

[root@linux /]# find /etc -name passwd/etc/passwd/etc/pam.d/passwd  -> this command will find files for starting like passwd under the /etc directory.

Using the “Locate” command:

     Locate command is faster than find command. Because it’s using a database which is previously built the database for search. Locate command will list all the path names which containing your search pattern.

The database is updated using corn or we can also manually update the database using below command.

#sudo updatedb

Example:

#locate mydata

Will see Configuring syslogd in Linux in this post

Follow the below steps on server:

Required services for syslogd

1. portmap
2 xinetd
3. syslog

Run the below command to keep on running above mentioned service after server reboot

#chkconfig portmap on
#chkconfig xinetd on
#chkconfig syslog on

Start portmap and xinetd services

#service portmap start
#service xinetd start

Check the service status

#service portmap status
#service xinetd status

Now edit “/etc/sysconfig/syslog” file using vi editor

#vi /etc/sysconfig/syslog

find for SYSLOGD_OPTIONS=”-m 0″

and add -r option to accept the logs from system

SYSLOGD_OPTIONS=”-r -m 0″

save and quit from the file :wq

-x disable DNS lookups on messages with -r option
-m 0 disabled MARK messages
-r enables logging

Once edited the file restart the syslog service

#service syslog retsrat

Follow the steps on client

Edit /etc/syslog.conf file and add a entry at end of file for server as shown below.

:Lets assume server ip as 192.168.1.10

#vi /etc/syslog.conf
user.* @192.168.1.10

Save and quit from the file :wq

now restart the syslog service on client

#service syslog restart

Now restart the client and check log entry in server. it will generate logs in server.

Checking logs on server

#less /var/log/messages

end of this log file you can see the recent logs.

#ls -l | ask '{print $2}'

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We are going to see YUM Configuration in RHEL7/ CentOS 7 in this post.

In Linux mostly we are using RPM and Yum Package management.

YUM- Yellowdog Updater Modified

Yum is mostly used to install a package without fail by resolving software dependencies.

We can configure yum locally/in network

Required RPM:
1. Yum
2. Createrepo
3. deltarpm
4. python-deltarpm

Configuring YUM in RHEL7

1. Insert RHEL7 media and mount it under /mnt

#mount /dev/cdrom /mnt

2. All the RPM’s available under Packages directory. change to Package Directory and
copy all the RPM’s under any local directory which you have already created.

3. Creating local directory to use as repository

#mkdir /yumpkg

4. Copying RPM’s from media to local directory

#cd /mnt/Packages
#cp *.* /yumpkg

5. Ensure all the required RPM’s installed or not by using below commands

#rpm -qa yum
#rpm -qa createrepo

6. Generate local repository files from yumpkg and create xml file