Install java on Linux centos

In this tutorial we will quickly setup java on linux centos,

We will be using the yum command to download the openjdk 1.8 and install

[vamshi@node01 ~]$ sudo yum install java-1.8.0-openjdk.x86_64

We have installed the java openjdk 1.8 and we can check the version using java -version

[vamshi@node01 ~]$ java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)


We make use of the alternatives command in centos which lists if we have any other version of java installed on the machine, and then enabling the default java version on the system wide.

[vamshi@node01 ~]$ alternatives --list | grep java
java auto /usr/lib/jvm/java-1.8.0-openjdk-
jre_openjdk auto /usr/lib/jvm/java-1.8.0-openjdk-
jre_1.8.0 auto /usr/lib/jvm/java-1.8.0-openjdk-
jre_1.7.0 auto /usr/lib/jvm/java-1.7.0-openjdk-
[vamshi@node01 ~]$ sudo alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
*  1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-
 + 2           java-1.7.0-openjdk.x86_64 (/usr/lib/jvm/java-1.7.0-openjdk-

Enter to keep the current selection[+], or type selection number: 1

This enabled openjdk1.8 to be the default version of java.

Setting JAVA_HOME path
In order to set the system JAVA_HOME path on the system we need to export this variable, for the obvious reasons of other programs and users using the classpath such as while using maven or a servlet container.

Now there are two levels we can setup the visibility of JAVA_HOME environment variable.
1. Setup JAVA_HOME for single user profile
We need to update the changes to the ~/.bash_profile

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-


export PATH

Now we need enforce the changes with reloading the .bash_profile with a simple logout and then login into the system or we can source the file ~/.bash_profile as follows:

[vamshi@node01 ~]$ source .bash_profile

Verifying the changes:

[vamshi@node01 ~]$ echo $PATH

2. Setup JAVA_HOME for the system wide profile and available to all the users.

[vamshi@node01 ~]$ sudo sh -c "echo -e 'export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-' > /etc/profile.d/"

This echo command writes the JAVA_HOME path to the system profile.d and creates a file which is read system wide level.

Ensure the changes are written to /etc/profile.d/

[vamshi@node01 ~]$ cat /etc/profile.d/
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-

Now source to apply the changes immediately to the file /etc/profile.d/ as follows

[vamshi@node01 ~]$ sudo sh -c ' source /etc/profile.d/ '

Or login to the root account and run the source command

Ensure to run the env command

[vamshi@node01 ~]$ env  | grep JAVA_HOME

How do I download and install Java on CentOS?

Install Java On CentOS

  1. Install OpenJDK 11. Update the package repository to ensure you download the latest software: sudo yum update. …
  2. Install OpenJRE 11. Java Runtime Environment 11 (Open JRE 11) is a subset of OpenJDK. …
  3. Install Oracle Java 11. …
  4. Install JDK 8. …
  5. Install JRE 8. …
  6. Install Oracle Java 12.

Is Java installed on CentOS?

OpenJDK, the open-source implementation of the Java Platform, is the default Java development and runtime in CentOS 7. The installation is simple and straightforward.

How do I install Java on Linux?

  • Java for Linux Platforms
  • Change to the directory in which you want to install. Type: cd directory_path_name. …
  • Move the . tar. gz archive binary to the current directory.
  • Unpack the tarball and install Java. tar zxvf jre-8u73-linux-i586.tar.gz. The Java files are installed in a directory called jre1. …
  • Delete the . tar.

How do I install latest version of Java on CentOS?

To install OpenJDK 8 JRE using yum, run this command: sudo yum install java-1.8. 0-openjdk.

Where is java path on CentOS?

They usually reside in /usr/lib/jvm . You can list them via ll /usr/lib/jvm . The value you need to enter in the field JAVA_HOME in jenkins is /usr/lib/jvm/java-1.8.

How do I know if java is installed on CentOS 7?

  • To check the Java version on Linux Ubuntu/Debian/CentOS:
  • Open a terminal window.
  • Run the following command: java -version.
  • The output should display the version of the Java package installed on your system. In the example below, OpenJDK version 11 is installed.

Where is java path set in Linux?


  • Change to your home directory. cd $HOME.
  • Open the . bashrc file.
  • Add the following line to the file. Replace the JDK directory with the name of your java installation directory. export PATH=/usr/java/<JDK Directory>/bin:$PATH.
  • Save the file and exit. Use the source command to force Linux to reload the .

How do I install java 14 on Linux?

Installing OpenJDK 14

  • Step 1: Update APT. …
  • Step 2: Download and Install JDK Kit. …
  • Step 3: Check Installed JDK Framework. …
  • Step 4: Update Path to JDK (Optional) …
  • Step 6: Set Up Environment Variable. …
  • Step 7: Open Environment File. …
  • Step 8: Save Your Changes.

How do I know where java is installed on Linux?

This depends a bit from your package system … if the java command works, you can type readlink -f $(which java) to find the location of the java command. On the OpenSUSE system I’m on now it returns /usr/lib64/jvm/java-1.6. 0-openjdk-1.6. 0/jre/bin/java (but this is not a system which uses apt-get ).

How do I install java 11 on Linux?

Installing the 64-Bit JDK 11 on Linux Platforms

  1. Download the required file: For Linux x64 systems: jdk-11. interim. …
  2. Change the directory to the location where you want to install the JDK, then move the . tar. …
  3. Unpack the tarball and install the downloaded JDK: $ tar zxvf jdk-11. …
  4. Delete the . tar.

Signals in Linux; trap command – practical example

The SIGNALS in linux

The signals are the response of the kernel to certain actions generated by the user / by a program or an application and the I/O devices.
The linux trap command gives us a best view to understand the SIGNALS and take advantage of it.
With trap command can be used to respond to certain conditions and invoke the various activities when a shell receives a signal.
The below are the various Signals in linux.

vamshi@linuxcent :~] trap -l

Lets take a look at some Important SIGNALS and their categorization of them:

Job control Signals: These Signals are used to control the Queuing the waiting process
(18) SIGCONT, (19) SIGSTOP , (20) SIGSTP

Termination Signals: These signals are used to interrupt or terminate a running process

Async I/O Signals: These signals are generated when data is available on a Input/Output device or when the kernel services wishes to notify applications about resource availability.
(23) SIGURG,  (29) SIGIO,  (29) SIGPOLL.

Timer Signals: These signals are generated when application wishes to trigger timers alarms.

Error reporting Signals: These signals occur when running process or an application code endsup into an exception or a fault.
(1) SIGHUP, (4) SIGILL, (5) SIGTRAP, (7) SIGBUS, (8) SIGFPE,  (13) SIGPIPE,  (11) SIGSEGV, (24) SIGXCPU.

Trap command Syntax:

trap [-] [[ARG] SIGNAL]

ARG is a command to be interpreted and executed when the shell receives the signal(s) SIGNAL.

If no arguments are supplied, trap prints the list of commands associated with each signal.
to unset the trap a – is to be used followed by the [ARG] SIGNAL] which we will demonstrate in the following section.

How to set a trap on linux through the command line?

[vamshi@linuxcent ~]$ trap 'echo -e "You Pressed Ctrl-C"' SIGINT

Now you have successfully setup a trap:>

When ever you press Ctrl-c on your keyboard, the message “You Pressed Ctrl-C” gets printed.

[vamshi@linuxcent ~]$ ^CYou Pressed Ctrl-C
[vamshi@linuxcent ~]$ ^CYou Pressed Ctrl-C
[vamshi@linuxcent ~]$ ^CYou Pressed Ctrl-C

Now type the trap command and you can see the currently set trap details.

[vamshi@node01 ~]$ trap
trap -- 'echo -e "You Pressed Ctrl-C"' SIGINT
trap -- '' SIGTSTP
trap -- '' SIGTTIN
trap -- '' SIGTTOU

To unset the trap all you need to do is to run the following command,

[vamshi@node01 ~]$ trap - 'echo -e "You Pressed Ctrl-C"' SIGINT

The same can be evident from the below output:

[vamshi@node01 ~]$ trap
trap -- '' SIGTSTP
trap -- '' SIGTTIN
trap -- '' SIGTTOU
[vamshi@node01 ~]$ ^C
[vamshi@node01 ~]$ ^C

What is trap command in Linux?

A built-in bash command that is used to execute a command when the shell receives any signal is called `trap`. When any event occurs then bash sends the notification by any signal. Many signals are available in bash. The most common signal of bash is SIGINT (Signal Interrupt).

What is trap command in bash?

If you’ve written any amount of bash code, you’ve likely come across the trap command. Trap allows you to catch signals and execute code when they occur. Signals are asynchronous notifications that are sent to your script when certain events occur.

How do you Ctrl-C trap?

To trap Ctrl-C in a shell script, we will need to use the trap shell builtin command. When a user sends a Ctrl-C interrupt signal, the signal SIGINT (Signal number 2) is sent.

What is trap shell?

trap is a wrapper around the fish event delivery framework. It exists for backwards compatibility with POSIX shells. For other uses, it is recommended to define an event handler. The following parameters are available: ARG is the command to be executed on signal delivery.

What signals Cannot be caught?

There are two signals which cannot be intercepted and handled: SIGKILL and SIGSTOP.

How does shell trap work?

The user sets a shell trap. If the user is hit by a physical move, the trap will explode and inflict damage on the opposing Pokémon. The user sets a shell trap. If the user is hit by a physical move, the trap will explode and inflict damage on opposing Pokémon.

How do I wait in Linux?


  1. Creating a simple process.
  2. Using a special variable($!) to find the PID(process ID) for that particular process.
  3. Print the process ID.
  4. Using wait command with process ID as an argument to wait until the process finishes.
  5. After the process is finished printing process ID with its exit status.

How use stty command in Linux?

  1. stty –all: This option print all current settings in human-readable form. …
  2. stty -g: This option will print all current settings in a stty-readable form. …
  3. stty -F : This option will open and use the specified DEVICE instead of stdin. …
  4. stty –help : This option will display this help and exit.

Can I trap Sigkill?

You can’t catch SIGKILL (and SIGSTOP ), so enabling your custom handler for SIGKILL is moot. You can catch all other signals, so perhaps try to make a design around those. be default pkill will send SIGTERM , not SIGKILL , which obviously can be caught.

What signal is Ctrl D?

Ctrl + D is not a signal, it’s EOF (End-Of-File). It closes the stdin pipe. If read(STDIN) returns 0, it means stdin closed, which means Ctrl + D was hit (assuming there is a keyboard at the other end of the pipe).

How to Shutdown or Reboot a remote Linux Host from commandline

The Shutdown process in a Linux system is an intelligent chain process where in the system ensures the dependent process have successfully terminated.


Difference between the Halt and Poweroff in Linux?
What is a Cold Shutdown and Warm Shutdown?
Linux System System Halt : The Halt process instructs the hardware to Stop the functioning of the CPU. Can be referred as a Warm Shutdown.
Linux System Poweroff/Shutdown : The Poweroff function sends the ACPI(Advanced Configuration and Power Interface) to power down the system. Can be referred as a Cold Shutdown.

As you may be aware the Linux runtime environment is a duo combination of processes running in User space and the Kernel space, All the major system activities and resources are initiated and governed and terminated by Kernel space.
So we got the Kernel space and the User space, The kernel space is where all the reseurce related processes run, which follows a finite behaviour, and the the userspace where the processes are dependent on the user actions, most of the userspace programs depend on the kernel space and make a context switch to get the CPU scheduling and such..
So, In the sequence of Shutdown on a linux machine, the userspace processes are first terminated in a systematic fashion through the scripts triggered by the core systemd processes which ensures clean exit and termination all the processes.

The Linux system provides us quite a few commands to enforce fast shutdown or a graceful shutdown of the operating system, each having their own consequences.

Firstly the init or the systemd which is the pid 1 process is what controls the runlevel of the system and it determines which processes are launched and running in that runlevel

The init is a powerful command which executes the runlevel it is told to.
Here the init 0 proceeds to Power-off the machine

$ sudo init 0

Here the init 6 proceeds to Reboot the machine

$ sudo init 6

These commands are real quick as it triggers the kernel space shutdown invocation process.. most often resulting in unclean termination of processes resulting system recovery and journaling while booting.

The following commands Shutdown the machine in seconds after issuing the command But tend to follow the kill sequence and clean exit of the processed.

$ sudo shutdown
$ sudo poweroff
$ sudo systemctl poweroff

Prints a wall message to all users.
All the processes are killed and the volumes are unmounted or converted to be in Read-Only mode while system power off is in progress.
Puts the system into a complete poweroff mode cutting out power supply to the machine completely.

$ sudo halt
$ sudo systemctl halt

Prints a message of “System halted” and Puts the machine in halt mode
If the --force or -f when specified twice the operation is immediately executed without terminating any processes or unmounting any file systems and resulting in data loss

The servers can only be brought back online through physical poweron or Remote Power manager console such as IPMI or ILOM.

To reboot or [/code]systemctl kexec[/code] will to restart the operating system which is one power cycle or equivalent of shutdown followed by the startup.

$ sudo reboot

$ sudo systemctl kexec

$ sudo systemctl reboot

If the --force or -f when specified twice the operation is immediately executed without terminating any processes or unmounting any file systems and resulting in data loss


It is important to understand that the commands are all softlinks to systemctl shutdown command. and ensure in proper shutdown sequence process

[vamshi@linuxcent cp-command]$ ls -l /usr/sbin/halt
lrwxrwxrwx. 1 root root 16 Jan 13 14:41 /usr/sbin/halt -> ../bin/systemctl
[vamshi@linuxcent cp-command]$ ls -l /usr/sbin/reboot
lrwxrwxrwx. 1 root root 16 Jan 13 14:41 /usr/sbin/reboot -> ../bin/systemctl
[vamshi@linuxcent cp-command]$ ls -l /usr/sbin/poweroff
lrwxrwxrwx. 1 root root 16 Jan 13 14:41 /usr/sbin/poweroff -> ../bin/systemctl

It is important to observe that all the commands are softlink to the systemctl process, When issuing a shutdown or reboot

The best practice to poweroff the system by enabling broadcast the notification message to all the users connected actively either through the Pseudo remote connection terminal or TTY terminals, Demonstrated as follows:

$ sudo systemctl poweroff

# this writes an entry into the journal, the wtmp and broadcasts the shutdown message to all the users connected through PTS and TTY terminals

What is the difference between systemctl poweroff and systemctl halt ?

The Linux System when put to a Halt state, stops the all the applications and ensures they’re safely exited, filesystems and volumes are unmounted and it is taken into a halted state where in the power connection is still active. And Can only be brought  online with a power reset effectively with a simple reset.
The Halt process instructs the hardware to Stop the functioning of the CPU.
Commonly can be referred as a Warm Shutdown.

Below is the screenshot to demonstrate the same
systemctl halt command in linux

The Poweroff function sends the ACPI(Advanced Configuration and Power Interface) to power down the system.
The Linux System when put to a Poweroff state it becomes completely offline following the systematical clean termination of processes.. and power input is cut off to the external peripherals, which is also sometimes called as cold shutdown, and the startup cold start.
Commonly can be referred to as a Cold Shutdown.

If you found the article worth your time, Please share your inputs in the comments section and share your experiences with shutdown and reboot issues

Can I reboot Linux remotely?

How to shutdown the remote Linux server. You must pass the -t option to the ssh command to force pseudo-terminal allocation. The shutdown accepts -h option i.e. Linux is powered/halted at the specified time.

Can you reboot a server remotely?

Open command prompt, and type “shutdown /m \\RemoteServerName /r /c “Comments”“. … Another command to restart or shutdown the Server remotely is Shutdown /i. Type Shutdown /i on the command prompt and it will open another dialogue box.

What is the Linux command to reboot?

To reboot Linux using the command line:

  1. To reboot the Linux system from a terminal session, sign in or “su”/”sudo” to the “root” account.
  2. Then type “ sudo reboot ” to reboot the box.
  3. Wait for some time and the Linux server will reboot itself.

How do I reboot from remote desktop?

Procedure. Use the Restart Desktop command. Select Options > Restart Desktop from the menu bar. Right-click the remote desktop icon and select Restart Desktop.

What does sudo reboot do?

sudo is short for “Super-user Do”. It has no effect on the command itself (this being reboot ), it merely causes it to run as the super-user rather than as you. It is used to do things that you might not otherwise have permission to do, but doesn’t change what gets done.

How do I remotely turn on a Linux server?

Enter the BIOS of your server machine and enable the wake on lan/wake on network feature. …
Boot your Ubuntu and run “sudo ethtool -s eth0 wol g” assuming eth0 is your network card. …
run also “sudo ifconfig” and annotate the MAC address of the network card as it is required later to wake the PC.

How do I restart a terminal server remotely?

From the remote computer’s Start menu, select Run, and run a command line with optional switches to shut down the computer:
To shut down, enter: shutdown.
To reboot, enter: shutdown –r.
To log off, enter: shutdown –l

How do I send Ctrl Alt Del to remote desktop?

Press the “CTRL,” “ALT” and “END” keys at the same time while you are viewing the Remote Desktop window. This command executes the traditional CTRL+ALT+DEL command on the remote computer instead of on your local computer.

How do I remotely restart a server by IP address?

Type “shutdown -m \ [IP Address] -r -f” (without quotes) at the command prompt, where “[IP Address]” is the IP of the computer you want to restart. For example, if the computer you want to restart is located at 192.168. 0.34, type “shutdown -m \ 192.168.

How do I reboot from command prompt?

  1. From an open command prompt window:
  2. type shutdown, followed by the option you wish to execute.
  3. To shut down your computer, type shutdown /s.
  4. To restart your computer, type shutdown /r.
  5. To log off your computer type shutdown /l.
  6. For a complete list of options type shutdown /?
  7. After typing your chosen option, press Enter.

How does Linux reboot work?

The reboot command is used to restart a computer without turning the power off and then back on. If reboot is used when the system is not in runlevel 0 or 6 (i.e., the system is operating normally), then it invokes the shutdown command with its -r (i.e., reboot) option.

Git config setup on linux; Unable to pull or clone from git; fatal: unable to access git; Peer’s Certificate has expired

Facing an issue with pulling the repository while dealing with an expired SSL certificate.

[vamshi@workstation ~]$ git pull
fatal: unable to access '': Peer's Certificate has expired.
[vamshi@workstation ~]$

SSL error while cloning git URL

If you have faced the error, then we can work around it by ignoring SSL certificate check and continue working with the git repo.

[vamshi@workstation ~]$ git clone
Cloning into 'pipeline-101'...
fatal: unable to access '': Peer's Certificate has expired.

It doesn’t allow the clone or pull or push to the gitlab website as its certificate is not valid, and the certificate is unsigned by a Valid CA. In most cases, we will have the corporate gitlab repo in our internal network and not publicly exposed.
We therefore trust the gitlab server as we have a bunch of our code on it.. Why not, I say?
We have to ensure to disable the check for the SSL certificate verification

Set the Variable GIT_SSL_NO_VERIFY=1 or GIT_SSL_NO_VERIFY=false and try to execute your previous command.

[vamshi@workstation ~]$ GIT_SSL_NO_VERIFY=1 git clone
Cloning into 'pipeline-101'...
Username for '': vamshi
Password for 'https://[email protected]': 
remote: Enumerating objects: 3, done.
remote: Counting objects: 100% (3/3), done.
remote: Total 3 (delta 0), reused 0 (delta 0)
Unpacking objects: 100% (3/3), done.

Make a permanent entry to system wide user level profiles as below. The following change works at the system level

[vamshi@workstation ~]$ sudo bash -c "echo -e export GIT_SSL_NO_VERIFY=1 > /etc/profile.d/ "
[vamshi@workstation ~]$ cat /etc/profile.d/
export GIT_SSL_NO_VERIFY=false

The practical use case of setting the environment variable can be made while building container images, using  the GIT_SSL_NO_VERIFY false as an environment variable in Dockerfile and building an image.

[vamshi@workstation ~]$ cat Dockerfile
FROM jetty:latest

We can also setup the container build agent with Jenkins Pipeline code with similar configuration to fetch a gitrepo in our next sessions.

Why is git clone not working?

If you have a problem cloning a repository, or using it once it has been created, check the following: Make sure that the path in the git clone call is correct. … If you have an authorization error, have an administrator check the ACLs in Administration > Repositories > <repoName> > Access.

How do I fix fatal unable to access?

How to resolve “git pull,fatal: unable to access ‘… \’: Empty reply from server”

  1. If you have configured your proxy for a VPN, you need to login to your VPN to use the proxy.
  2. to use it outside the VPN use the unset command: git config –global –unset http.proxy.

How do I bypass SSL certificate in git?

Prepend GIT_SSL_NO_VERIFY=true before every git command run to skip SSL verification. This is particularly useful if you haven’t checked out the repository yet. Run git config http. sslVerify false to disable SSL verification if you’re working with a checked out repository already.

How do I open a cloned git repository?

Clone Your Github Repository

  • Open Git Bash. If Git is not already installed, it is super simple. …
  • Go to the current directory where you want the cloned directory to be added. …
  • Go to the page of the repository that you want to clone.
  • Click on “Clone or download” and copy the URL.

Can not clone from GitHub?

If you’re unable to clone a repository, check that:
You can connect using HTTPS. For more information, see “HTTPS cloning errors.”
You have permission to access the repository you want to clone. For more information, see “Error: Repository not found.”
The default branch you want to clone still exists.

Do I need git for GitLab?

To install GitLab on a Linux server, you first need Git software. We explain how to install Git on a server in our Git tutorial. Next, you should download the GitLab omnibus package from the official GitLab website.

How do I clone a project from GitHub?

Cloning a repository

  • In the File menu, click Clone Repository.
  • Click the tab that corresponds to the location of the repository you want to clone. …
  • Choose the repository you want to clone from the list.
  • Click Choose… and navigate to a local path where you want to clone the repository.
  • Click Clone.

How do I push code to GitHub?

Using Command line to PUSH to GitHub

  • Creating a new repository. …
  • Open your Git Bash. …
  • Create your local project in your desktop directed towards a current working directory. …
  • Initialize the git repository. …
  • Add the file to the new local repository. …
  • Commit the files staged in your local repository by writing a commit message.

chown and chgrp commands to change ownership of files and directories in Linux

The commands chown and chgrp are extensively used in linux systems to update the ownership and organize the file structure.

The chown command can be implemented in the following two types of notations.
1) User and group owner Symbolic notation
2) Reference operator

The options/filters will be common to them for the two kinds on notations, We will look at the practical and important options.
The chown command syntax:

chown <username> <data-directory> <files>
chown <username>:<groupname> <data-directory>
chown --reference <Source-reference-file| Source-reference-Directory> <data-directory>

The ownership of the files is a privileged operation and it requires a sudo access to the system
Lets start by running the chown command on the files you want to change the ownership
We have a file called jdk-8u141-linux-x64.rpm and its owned by root user.

[vamshi@linuxcent ~]$ ls -l jdk-8u141-linux-x64.rpm
-rw-r--r--. 1 root root 169980729 Jul 13 2017 jdk-8u141-linux-x64.rpm

We intend to change the ownership to user vamshi and we use chown command

[vamshi@linuxcent ~]$ sudo chown -v vamshi jdk-8u141-linux-x64.rpm 
changed ownership of ‘jdk-8u141-linux-x64.rpm’ from root to vamshi
[vamshi@linuxcent ~]$ ls -l jdk-8u141-linux-x64.rpm
-rw-r--r--. 1 vamshi root 169980729 Jul 13  2017 jdk-8u141-linux-x64.rpm

By this only the user part of ownership was modified but the group was uneffected.

NOTE: We are using the option -v to print the command output information in verbose mode.

We can use chgrp command to modify the group ownership as follows:

[vamshi@linuxcent ~]$ sudo chgrp -v vamshi jdk-8u141-linux-x64.rpm 
changed group of ‘jdk-8u141-linux-x64.rpm’ from root to vamshi

To change both the user owner and group at once, chown command can be used, as demonstrated below:

[vamshi@linuxcent ~]$ sudo chown -v vamshi:vamshi jdk-8u141-linux-x64.rpm 
changed ownership of ‘jdk-8u141-linux-x64.rpm’ from root:root to vamshi:vamshi

[vamshi@linuxcent ~]$ ls -l jdk-8u141-linux-x64.rpm
-rw-r--r--. 1 vamshi vamshi 169980729 Jul 13 2017 jdk-8u141-linux-x64.rpm

How do you recursively change the permissions within the destination sub-directories and files ?

chown command when used with -R applies the updated ownership recursively till the directory depth on destination.

[vamshi@linuxcent data]$ ls -ld redmine/
drwxr-xr-x. 3 root root 17 Apr 17 16:31 redmine/
[vamshi@linuxcent data]$ sudo chown vamshi:vamshi /mnt/data/redmine/ -R
[vamshi@linuxcent data]$ ls -ld /mnt/data/redmine/
drwxrwxr-x. 3 vamshi vamshi 17 Apr 17 16:31 redmine-4.0.6

How to apply reference permissions to chown command in Linux ?

We shall be using the option --reference which takes the reference from the existing file and applies the permission

Suppose we directory called djangoproject1.
The root user copied the contents from elsewhere and placed  them in the location /home/alice .
Now the user alice has to have the user ownership to them in-order to work with djangoproject1.

[root@node02 alice]# ls -ld djangoproject1
drwxrwxr-x. 3 root root 108 Apr 16 11:45 djangoproject1

We now file called requirements.txt and the file is owner by the user alice and has the owner following permissions

[root@node02 alice]# ls -lth alice-requirements.txt
-rw-rw-r--. 1 alice alice 130 Apr 17 15:54 alice-requirements.txt

So we can simply reference this file and apply the same ownership permissions to djangoproject1, Lets see the demonstration.

[root@node02 alice]# sudo chown --reference alice-requirements.txt djangoproject1/ -R

As a result we have successfully modified the user and group ownership to alice using the --reference operator; Applying the same ownership permissions as our reference file alice-requirements.txt.

[root@node02 alice]# ls -lthr djangoproject1/*
-rw-rw-r--. 1 alice alice 405 Apr 16 11:44 djangoproject1/
-rw-rw-r--. 1 alice alice 756 Apr 16 11:44 djangoproject1/
-rw-rw-r--. 1 alice alice 3.1K Apr 16 11:44 djangoproject1/
-rw-rw-r--. 1 alice alice 0 Apr 16 11:44 djangoproject1/
-rw-rw-r--. 1 alice alice 405 Apr 16 11:44 djangoproject1/

total 8.0K
-rw-rw-r--. 1 alice alice 2.3K Apr 16 11:45 settings.cpython-36.pyc
-rw-rw-r--. 1 alice alice 159 Apr 16 11:45 __init__.cpython-36.pyc

Thus we can use the chown command to update the ownership information to files and directories and also use the chgrp command as per requirement.

How do I use chgrp in Linux?

chgrp command in Linux is used to change the group ownership of a file or directory. All files in Linux belong to an owner and a group. You can set the owner by using “chown” command, and the group by the “chgrp” command.

Who can use the chgrp command?

You must use sudo with chgrp . Groups are not owned by users, so whether a file or directory is moved from one group to another is not a decision that sits with the average user. That’s a job for someone with root privileges.

What is the difference between chown and chgrp?

The chown command is used to change file or directory ownership. … Actually the chown command can be used to change both user and group ownership, while the chgrp command can only be used to change group ownership.

Is chgrp recursive?

To recursively change the group ownership of all files and directories under a given directory, use the -R option. Other options that can be used when recursively changing the group ownership are -H and -L . If the argument passed to chgrp command is a symbolic link, the -H option will cause the command to traverse it.

What does Chgrp mean in Linux?

The chgrp (from change group) command may be used by unprivileged users on Unix-like systems to change the group associated with a file system object (such as a file, directory, or link) to one of which they are a member.

How do you give ownership in Linux?

How to Change the Owner of a File

  1. Become superuser or assume an equivalent role.
  2. Change the owner of a file by using the chown command. # chown new-owner filename. new-owner. Specifies
  3. the user name or UID of the new owner of the file or directory. filename. …
    Verify that the owner of the file has changed. # ls -l filename.

What is G’s permission in Linux?

chmod g+s .; This command sets the “set group ID” (setgid) mode bit on the current directory, written as . . This means that all new files and subdirectories created within the current directory inherit the group ID of the directory, rather than the primary group ID of the user who created the file.

How do you ping on Linux?

Click or double-click the Terminal app icon—which resembles a black box with a white “>_” in it—or press Ctrl + Alt + T at the same time. Type in the “ping” command. Type in ping followed by the web address or IP address of the website you want to ping.

Who can access a file with permission 000?

File with 000 permission can be read / written by root. Everybody else cannot read / write / execute the file.

What are the chown and chgrp commands used for?

The chown command changes the owner of a file, and the chgrp command changes the group. On Linux, only root can use chown for changing ownership of a file, but any user can change the group to another group he belongs to.

How do you chown chgrp?

Stupid simple command to change ownership (chown) and change group (chgrp) at the same time. To simultaneously change both the owner and group of files or directories in linux use the following command structure: chown someusername:somegroupname filename.

What do you mean by chmod chown and chgrp commands give example for each?

These permissions read, write and execute permission for owner, group, and others. … Example: Give read/write/execute permission to the user, read/execute permission to the group, and execute permission to others. $ chmod 751 file1. #2) chown: Change ownership of the file.

Housekeeping on gitlab and practical examples using gitlab-ctl

In this section we will see some important housekeeping tasks while maintaining gitlab server.

We will list out some of the important configuration services present in gitlab and best housekeeping tips.
The important configuration file for gitlab is: /opt/gitlab/embedded/service/gitlab-rails/config/gitlab.yml
Once the changes are made to this file it should be followed up running the reconfigure to apply the changes.
The chef server reads the config files and then updates the system wide configuration resources.

Reconfiguring the gitlab

[vamshi@gitlab ~]$ sudo gitlab-ctl reconfigure

This command reloads the configuration from the configuration files and also migrated if any changes regiuired to the Postgresql database.

View all the current logs run the gitlab-ctl tail command.

[vamshi@node01 ~]$ sudo gitlab-ctl tail
==> /var/log/gitlab/gitlab-shell/gitlab-shell.log <==

==> /var/log/gitlab/gitlab-rails/sidekiq.log <==
2020-04-o2_13:30:24.29475 2020-04-02T13:30:24.293Z 8872 TID-or0k2ve5w PagesDomainVerificationCronWorker JID-e46ed1d452563ca9b7d4adca INFO: done: 0.357 sec

This in one of the first command you need when troubleshooting your gitlab server..
This prints the logs from various components present in gitlab and you as an administrator will be able to effectively identify the issues.
To start the interactive ruby console and debug mostly used for Database interaction operations, it takes -e as argument and takes you to the production environment. -s takes you to the sandbox environment.

gitlab-rails console <-e|-s> [environment]

For example we can get the complete gitlab information using the following gitlab:env:info:

[vamshi@gitlab ~]$ sudo gitlab-rails gitlab:env:info
[sudo] password for vamshi:

System information
Proxy: no
Current User: git
Using RVM: no
Ruby Version: 2.5.3p105
Gem Version: 2.7.6
Bundler Version:1.17.3
Rake Version: 12.3.2
Redis Version: 3.2.12
Git Version: 2.18.1
GitLab information
Version: 11.10.4-ee
Revision: 88a3c791734

GitLab Shell
Version: 9.0.0


Some more important commands for gitlab Houseeping:

[vamshi@gitlab ~]$ sudo gitlab-rails gitlab:check
[sudo] password for vamshi:
Checking GitLab subtasks ...

Checking GitLab Shell ...


How to restart the gitlab serer from command line ?

[vamshi@gitlab ~]$ sudo gitlab-rails restart

How to clear the gitlab logs by truncating them to Zero bytes?

[vamshi@gitlab ~]$ sudo gitlab-rails log:clear

How To print the high level stats of gitlab server?

[vamshi@gitlab ~]$ sudo gitlab-rails stats

What is GitLab housekeeping?

GitLab supports and automates housekeeping tasks within your current repository such as: Compressing Git objects. Removing unreachable objects.

What is GitLab housekeeping?

How do I clean up GitLab repository?

  • To clean up a repository:
  • Go to the project for the repository.
  • Navigate to Settings > Repository.
  • Upload a list of objects. For example, a commit-map file created by git filter-repo which is located in the filter-
  • repo directory. …
  • Click Start cleanup.

What is Git repack?

DESCRIPTION. This command is used to combine all objects that do not currently reside in a “pack”, into a pack. It can also be used to re-organize existing packs into a single, more efficient pack.

What does Git prune do?

The git prune command is an internal housekeeping utility that cleans up unreachable or “orphaned” Git objects. Unreachable objects are those that are inaccessible by any refs. Any commit that cannot be accessed through a branch or tag is considered unreachable.

How do I know if GitLab is running?

When a user goes to your GitLab URL, they will be shown an arbitrary Deploy in progress page. To remove the page, you simply run sudo gitlab-ctl deploy-page down . You can also check the status of the deploy page with sudo gitlab-ctl deploy-page status.

How do I maintain a Git repository?

Manually reviewing large files in your repository

  • Download the script to your local system.
  • Put it in a well known location accessible to your Git repository.
  • Make the script an executable: …
  • Clone the repository to your local system.
  • Change directory to your repository root.
  • Run the Git garbage collector manually.

How do I purge Gitlab?

uninstall Gitlab:

  1. Stop the gitlab service. Command : sudo gitlab-ctl stop.
  2. Start commonde of service facility. command : sudo gitlab-ctl uninstall.
  3. Delete the package of gitlab. command : Locat gitlab.
  4. restart machine.

How do I empty a Gitlab project?

Delete a project

  1. On the top bar, select Menu > Projects and find your project.
  2. On the left sidebar, select Settings > General.
  3. Expand Advanced.
  4. In the “Delete project” section, select Delete project.
  5. Confirm the action when asked to.

Are git repos compressed?

Thirdly, Git stores its data as compressed objects, whereas SVN stores them as uncompressed copies. Go into any . svn/text-base directory, and you’ll find uncompressed copies of the (base) files.

kubernetes bash completion

Wouldn’t it be great when we are using kubernetes and just tab to get a list of possible subcommands?

We have the extended facility to automatically tab and get the kubectl command suggestions, This feature is inbuilt into the kubectl and kubeadmin, All we need to just extract the script and enable it to the .bash_profile and source it. Lets do it as show below

[vamshi@workstation ~]$ kubectl completion bash > ~/.kube/
[vamshi@workstation ~]$ echo -e "\n#kubectl shell completion\nsource '$HOME/.kube/'\n" >> $HOME/.bash_profile
[vamshi@workstation ~]$ source $HOME/.bash_profile

Once you have successfully sourced the .bash_profie file.. type kubectl commands and keep tabbing all the way to get the suitable suggestions.

What is kubectl bash completion?

The kubectl completion script for Bash can be generated with the command kubectl completion bash . … However, the completion script depends on bash-completion, which means that you have to install this software first (you can test if you have bash-completion already installed by running type _init_completion ).

How do I create a completion in bash?

How to add bash auto completion in Ubuntu Linux

  1. Open the terminal application.
  2. Refresh package database on Ubuntu by running: sudo apt update.
  3. Install bash-completion package on Ubuntu by running: sudo apt install bash-completion.
  4. Log out and log in to verify that bash auto completion in Ubuntu Linux working properly.

What is kubectl auto completion?

Shell command-line completion allows you to quickly build your command without having to type every character. … The Kubernetes documentation provides great instructions on how to set it up for your development environment.

How do you use kubectl autocomplete?

To use shell autocompletion with kubectl simply press tab while writing out a command. For example we can type g and then press tab to autocomplete to get .

What is difference between Docker and Kubernetes?

A fundamental difference between Kubernetes and Docker is that Kubernetes is meant to run across a cluster while Docker runs on a single node. … Kubernetes pods—scheduling units that can contain one or more containers in the Kubernetes ecosystem—are distributed among nodes to provide high availability.

Is zsh better than bash?

It has many features like Bash but some features of Zsh make it better and improved than Bash, such as spelling correction, cd automation, better theme, and plugin support, etc. Linux users don’t need to install the Bash shell because it is installed by default with Linux distribution.

How does bash completion work?

The programmable completion feature in Bash permits typing a partial command, then pressing the [Tab] key to auto-complete the command sequence. [1] If multiple completions are possible, then [Tab] lists them all. Let’s see how it works. Tab completion also works for variables and path names.

How do I know if bash completion is installed?

If the autocomplete results contain directories only (no files), then Bash Completion is installed. If the autocomplete results include files, then Bash Completion is not installed.

What is complete command?

complete is a bash command used to perform the auto-complete action when the user hit the TAB key in a terminal. Calling just complete will list all the functions registered for auto-completion of commands or services options.

What is the difference between Minikube and Kubernetes?

Kubernetes is an open source orchestration system for Docker containers. … On the other hand, minikube is detailed as “Local Kubernetes engine”. It implements a local Kubernetes cluster on macOS, Linux, and Windows.

How do I know if kubectl is installed?

Install the kubectl Command Line

  1. Check that kubectl is correctly installed and configured by running the kubectl cluster-info command: kubectl cluster-info. …
  2. You can also verify the cluster by checking the nodes. …
  3. To get complete information on each node, run the following: kubectl describe node.

Docker Networking basics and the types of networks

The docker networking comprises of a overlay network and enabled communication with the outside resources using it.

There are following main types of built in connectivity networking drivers namely the bridged, host, macvlan, overlay network and the null driver with no network.

The docker container networking Model CNM architecture manages the networking for Docker container.

IPAM which stands for the IP address management works in a single docker node, and aids in Enabling the network connectivity among the doccker containers. Its primary responsibility is to allocate the IP address space for the subnets, allocation of the IP addresses to the endpoints and the network etc,.

The networking in docker is essentially an isolated sandbox environment, The isolation of the networking resources is possible by the namespaces

The overlay network enables the communication enabled the network spanning across many docker nodes on an environment like the Docker swarm network, The same networking logic is evident in a bridge networking but it is ony limited to a single docker host unlike the overlay network.

Here’s the output snippet from the docker info command; Listing the available network drivers.

# docker info
 Volume: local
 Network: bridge host macvlan null overlay

The container networking enables connectivity inbetween the docker containers and also the host machine to docker container and vice-versa.

Listing the default networks in docker:

[vamshi@node01 nginx]$ docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
68b2ffd36e8f        bridge              bridge              local
c1aca4c87a2b        host                host                local
d5e48683def8        none                null                local

When a container is created by default it connects to the bridge network unless an extra arguments are specified.

When you install the docker by default a docker0 virtual interface is created which behaves as a bridge between the docker containers and the host system.

[vamshi@node01 nginx]$ brctl show
bridge name	bridge id		STP enabled	interfaces
docker0		8000.0242654b42ef	no

For brctl command we need to Install the bridge-util package.

We now examine the docker networks with docker network inspect.

Inspecting the various docker networks:

Inspecting the bridge network:

The bridge networking enables the network connectivity over the dockers in a single docker server host.

[vamshi@node01 nginx]$ docker network inspect bridge
        "Name": "bridge",
        "Id": "68b2ffd36e8fcdc0c3b170dfdbdbc93bb58351d1b2c011abc80709928463f809",
        "Created": "2020-05-23T10:28:27.206979057Z",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                    "Subnet": "",
                    "Gateway": ""
        "Internal": false,
        "Attachable": false,
        "Containers": {},
        "Options": {
            "": "true",
            "": "true",
            "": "true",
            "": "",
            "": "docker0",
            "": "1500"
        "Labels": {}

This bridge is shown with the ip addr command as follows:

# ip addr show docker0 
   docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default 
    link/ether 02:42:65:4b:42:ef brd ff:ff:ff:ff:ff:ff
    inet scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:65ff:fe4b:42ef/64 scope link 
       valid_lft forever preferred_lft forever

Inspecting the host network.

[vamshi@node01 ~]$ docker network inspect host 
        "Name": "host",
        "Id": "c1aca4c87a2b3e7db4661e0cdedc97245cd5dfdc8aa2c9e6fa4ff1d5ecf9f3c1",
        "Created": "2019-05-16T18:46:19.485377974Z",
        "Scope": "local",
        "Driver": "host",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": []
        "Internal": false,
        "Attachable": false,
        "Containers": {},
        "Options": {},
        "Labels": {}

Inspecting the null driver network

[vamshi@node01 ~]$ docker network inspect none
        "Name": "none",
        "Id": "d5e48683def80b2e739b3be95e58fb11abc580ce29a33ba0df679a7a3972f532",
        "Created": "2019-05-16T18:46:19.477155061Z",
        "Scope": "local",
        "Driver": "null",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": []
        "Internal": false,
        "Attachable": false,
        "Containers": {},
        "Options": {},
        "Labels": {}


The following are special networking architectures to span across multihost docker servers enabling network connectivity among the docker containers.

1.Overlay network

2 macvlan network.

Let us inspect the multi host networking:

The core components of the docker interhost network consists of

Inspecting the overlay network:

[vamshi@docker-master ~]$ docker network inspect overlay-linuxcent 
        "Name": "overlay-linuxcent",
        "Id": "qz5ucx9hthyva53cydei0y8yv",
        "Created": "2020-05-25T13:22:35.087032198Z",
        "Scope": "swarm",
        "Driver": "overlay",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                    "Subnet": "",
                    "Gateway": ""
        "Internal": false,
        "Attachable": false,
        "Containers": {
            "ingress-sbox": {
                "Name": "overlay-linuxcent-endpoint",
                "EndpointID": "165beb97b22c2857e3637119016ef88e462a05d3b3251c4f66aa0fc9176cfe67",
                "MacAddress": "02:42:0a:ff:00:03",
                "IPv4Address": "",
                "IPv6Address": ""
        "Options": {
            "": "4096"
        "Labels": {},
        "Peers": [
                "Name": "",
                "IP": ""

The endpoint is the Virtual IP addressing that routes the traffic to the respective containers running on individual docker nodes.

Inspecting the macvlan network:

vamshi@docker-master ~]$ docker network inspect macvlan-linuxcent 
        "Name": "macvlan-linuxcent",
        "Id": "99c6a20bd4029ce5a37139c6e6792ec4f8a075c94b5f3e71efc32d92d41f3f89",
        "Created": "2020-05-25T14:20:00.655299409Z",
        "Scope": "local",
        "Driver": "macvlan",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": {},
            "Config": [
                    "Subnet": "",
                    "Gateway": ""
        "Internal": false,
        "Attachable": false,
        "Containers": {},
        "Options": {},
        "Labels": {}

What is Docker networking?

Docker networking is primarily used to establish communication between Docker containers and the outside world via the host machine where the Docker daemon is running. … You can run hundreds of containers on a single-node Docker host, so it’s required that the host can support networking at this scale.

How does networking work with Docker?

Docker secures the network by managing rules that block connectivity between different Docker networks. Behind the scenes, the Docker Engine creates the necessary Linux bridges, internal interfaces, iptables rules, and host routes to make this connectivity possible.

How do I connect to a Docker network?

Connect a container to a network when it starts

You can also use the docker run –network= option to start a container and immediately connect it to a network.

Can a Docker container have multiple networks?

You can create multiple networks with Docker and add containers to one or more networks. Containers can communicate within networks but not across networks. A container with attachments to multiple networks can connect with all of the containers on all of those networks.

Why is docker network needed?

Some of the major benefits of using Docker Networking are: They share a single operating system and maintain containers in an isolated environment. It requires fewer OS instances to run the workload. It helps in the fast delivery of software.

What are the types of docker networks?

There are three common Docker network types – bridge networks, used within a single host, overlay networks, for multi-host communication, and macvlan networks which are used to connect Docker containers directly to host network interfaces.

How do I ping a Docker container?

Ping the IP address of the container from the shell prompt of your Docker host by running ping -c5 . Remember to use the IP of the container in your environment. The replies above show that the Docker host can ping the container over the bridge network.

What does Docker network create do?

When you install Docker Engine it creates a bridge network automatically. This network corresponds to the docker0 bridge that Engine has traditionally relied on. When you launch a new container with docker run it automatically connects to this bridge network.

Does Docker offer support for IPv6?

Before you can use IPv6 in Docker containers or swarm services, you need to enable IPv6 support in the Docker daemon. Afterward, you can choose to use either IPv4 or IPv6 (or both) with any container, service, or network. Note: IPv6 networking is only supported on Docker daemons running on Linux hosts.

How do I run a docker on a local network?

This article discusses four ways to make a Docker container appear on a local network.

  • Using NAT
  • It will create a veth interface pair.
  • Connect one end to the docker0 bridge.
  • Place the other inside the container namespace as eth0 .
  • Assign an ip address from the network used by the docker0 bridge.

Can a docker container have its own ip address?

The answer is: you can configure it. Create the container with –network host and it will use the host ip.


The ENTRYPOINT or CMD usually determine the single and main startup process inside the running container, The ENTRYPOINT and the CMD are the final Docker DSL invocation statements in a Dockerfile.A Dockerfile can not be complete without either one of them.

Both the ENTRYPOINT and CMD will execute a /bin/sh -c , but have significant differences.

ENTRYPOINT usually is straight forward with the and is often the statement that enables the  docker image as a runnable container. The ENTRYPOINT statement doesnot let the run time arguments get overwritten during the container runtime, instead the commands are passed on as arguments to the ENTRYPOINT, for Example when the container is started as docker run my-image -d, then the resultant -d argument is passed on as an argument to the ENTRYPOINT.
It means that only last ENTRYPOINT statement is valid in the Dockerfile

The ENTRYPOINT takes CMD as its arguments.

ENTRYPOINT command arg1 arg2


CMD ["arg1", "arg2"]
ENTRYPOINT ["java","-jar","app.jar"]
CMD ["-Dserver.port=8080"]

CMD on the other hand is subversive to the ENTRYPOINT.
CMD start statement can be overwritten with container arguments during the container runtime. The CMD does not execute anything at the build time.

CMD ["command","arg1", "arg2"]
CMD ["java","","-jar","-Dserver.port=8080","app.jar"]

The major practical use with CMD is that the you will be able to overwrite the docker runtime command line arguments but you cannot override with you have ENTRYPOINT.

The CMD will be very beneficial in cases which require sending arguments to containers in runtime which in development and QA stages and is great for debugging environments.

The [] are not mandatory for ENTRYPOINT and CMD instruction statements inside Dockerfile but can be given for better readability when you have lot of arguments

What is the difference between CMD and run in Dockerfile?

RUN is an image build step, the state of the container after a RUN command will be committed to the container image. A Dockerfile can have many RUN steps that layer on top of one another to build the image. CMD is the command the container executes by default when you launch the built image.

What is the use of CMD in docker?

The CMD command​ specifies the instruction that is to be executed when a Docker container starts. This CMD command is not really necessary for the container to work, as the echo command can be called in a RUN statement as well. The main purpose of the CMD command is to launch the software required in a container.

What is docker ENTRYPOINT script?

entrypoint scripts are plugins that can be written in any language. inherited images can add to existing entrypoint scripts by simply adding to the /docker-entrypoint.

What is the purpose of ENTRYPOINT in Dockerfile?

In Dockerfiles, an ENTRYPOINT instruction is used to set executables that will always run when the container is initiated. Unlike CMD commands, ENTRYPOINT commands cannot be ignored or overridden—even when the container runs with command line arguments stated.

Can Dockerfile have multiple ENTRYPOINT?

According to the documentation however, there must be only one ENTRYPOINT in a Dockerfile.

What is Docker ENTRYPOINT Initdb?

3. 3. /docker-entrypoint-initdb. d/init. sql is executed the moment your database container starts running, while your is executed the moment your web container starts running.

Does docker start run ENTRYPOINT?

So yes, the ‘ CMD ‘ commands are executed after a ‘ docker start ‘.

Can Dockerfile have multiple CMD?

You are right, the second Dockerfile will overwrite the CMD command of the first one. Docker will always run a single command, not more. So at the end of your Dockerfile, you can specify one command to run.

What is in docker Run command?

The docker run command creates a container from a given image and starts the container using a given command. It is one of the first commands you should become familiar with when starting to work with Docker.

What is difference between CMD and entrypoint?

In a nutshell: CMD sets default command and/or parameters, which can be overwritten from command line when docker container runs. ENTRYPOINT command and parameters will not be overwritten from command line. Instead, all command line arguments will be added after ENTRYPOINT parameters.

What is the default entrypoint for docker?

/bin/sh -c
Docker defaults the entrypoint to /bin/sh -c . This means you’ll end up in a shell session when you start the container.

Create a new User in Jenkins

Login to the Jenkins and navigate to the Manage Jenkins -> Manage Users. Now you will be able to see the current users on the Jenkins.

You should be able to land on the URL similar to this:

On the Left hand side menu Click on Create User and follow the process. .
With this process you will be able to create a new user using the Jenkins’s own user database.

You can also ensure the Jenkins system user details from the jenkins server by navigating to the path $JENKINS_HOME and from the file users/users.xml

[root@node02 jenkins]# grep -w builduser * users/users.xml 2>/dev/null 
users/users.xml: <string>builduser</string>

How do I give user access to Jenkins?

Essentially you do this:

  • Go to Jenkins -> Manage Jenkins -> Configure Global Security.
  • Check “Enable security”.
  • Set “Jenkins own user database” as security realm.
  • Check “Allow users to sign up”
  • Choose “Matrix based security”
  • Check “Overall read” on Anonymous.
  • Add your admin account in the matrix, check every box.

How do I make the first admin in Jenkins?

Jenkins – Security

  • Step 1 − Click on Manage Jenkins and choose the ‘Configure Global Security’ option.
  • Step 2 − Click on Enable Security option. …
  • Step 3 − You will be prompted to add your first user. …
  • Step 4 − It’s now time to setup your users in the system.

How get manage users in Jenkins?

When you go to manage Jenkins and scroll down, you will see the ‘Manage Users’ option. Click on this option. Step 2: Just Like, you defined the admin user, and start creating other users for the system.

How do I change users in Jenkins?

To change the jenkins user, open the /etc/sysconfig/jenkins (in debian this file is created in /etc/default) and change the JENKINS_USER to whatever you want. Make sure that user exists in the system (you can check the user in the /etc/passwd file ).

How do I create multiple users in Jenkins?

in jenkins go to Manage Jenkins > Configure Global Security and select the “Enable Security” check box. select “Jenkins Own User Database” for the security realm and then select “Logged in Users can do anything” or a matrix based strategy (If you have multiple users with different permissions) for the Authorization.

What user runs Jenkins?

Similar to access control for users, builds in Jenkins run with an associated user authorization. By default, builds run as the internal SYSTEM user that has full permissions to run on any node, create or delete jobs, start and cancel other builds, etc.

Is it possible to create users and define roles for them in Jenkins?

By default, Jenkins comes with very basic user creation options. You can create multiple users but can only assign the same global roles and privileges to them. The Role Strategy Plugin enable you to assign different roles and privileges to different users.

How do I give Jenkins a user root permission?

Below are the steps to achieve this.

  • #1 open /etc/sudoers. type sudo vi /etc/sudoers . This will open your file in edit mode.
  • #2 Add/Modify jenkins user. Look for the entry for jenkins user. Modify as below if found or add a new line. …
  • #3 Save and Exit from edit mode. Press ESC and type :wq and hit Enter .

Where does Jenkins Store users?

Jenkins stores the configuration for each job within an eponymous directory in jobs/. The job configuration file is config. xml, the builds are stored in builds/, and the working directory is workspace/.

How do I create a user and group in Jenkins?

Follow the steps below:

  • Log in to Jenkins using the existing administrative user account credentials.
  • Navigate to the “Manage Jenkins -> Manage Users” page.
  • Select the “Create User” option.
  • Enter a username, password, name and email address to create a new user. …
  • Save the new account.

Bash How to Loop through Files

Bash How to Loop through Files

You can use it for the loop. Here is the syntax: for ELEMENT in $ARRAY; do command; done

Let’s try in in live example. First, create a new directory:

mkdir /root/test
cd /root/test
touch /root/test/
touch /root/test/
touch /root/test/document.doc

Secondly, we process all files that have suffix .sh with for loop:

for FILE in /root/test/*.sh
do echo "Processing ${FILE} file.."

Output: Processing /root/test/ file.. Processing /root/test/ file..

Based on the results of output (above), we can see that the loop processes all files in the /root/test, which have the suffix .sh

If you want to process command-line arguments use:

for FILE in "$*"
echo "Processing $FILE" file.

$* expands to file names of all files in the current directory.