Category Archives: Linux

Find and replace text within a file on Linux

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To find and replace text within a file on Linux, you can use various command-line tools such as sed, awk, or even grep combined with sed. Here’s how you can do it using sed, which is one of the most commonly used tools for this purpose:

sed -i 's/old_text/new_text/g' filename

Explanation:

  • -i: This option edits files in place. If you want to create a backup of the original file, you can use -i.bak instead, which will create a backup with the extension .bak.
  • 's/old_text/new_text/g': This is the substitution command in sed. It tells sed to substitute old_text with new_text globally (i.e., all occurrences).
  • filename: Replace this with the name of the file you want to modify.

For example, if you want to replace all occurrences of “hello” with “world” in a file named example.txt, you would use:

sed -i 's/hello/world/g' example.txt

Make sure to use caution when using the -i option, as it directly modifies the file. Always double-check the results to ensure they are as expected. If you want to preview the changes before actually modifying the file, you can omit the -i option and redirect the output to a different file:

sed 's/old_text/new_text/g' filename > new_filename

This command will perform the replacement and save the modified content to a new file called new_filename, leaving the original file unchanged.

Databricks: Using COALESCE and SPLIT

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COALESCE – This command is popular among many different SQL dialects. We can use it to replace NULL values. For all NULL values in the Description column, COALESCE() will replace the null with a value you include in the function. In this case, the value is "Misc". For more information about COALESCE, check the documentation.

SPLIT – This command splits a string value around a specified character and returns an array. An array is a list of values that you can access by position. In this case, the forward slash (“/”) is the character we use to split the data. The first value in the array is the month. This list is zero-indexed for the index of the first position is 0. Since we want to pull out the first value as the month, we indicate the value like this: SPLIT(InvoiceDate, "/")[0] and rename the column month. The day is the second value and its index is 1.

The third SPLIT is different. Remember that our InvoiceDate column is a string that includes a date and time. Each part of the date is seperated by a forward slash, but between the date and the time, there is only a space. Line 10 contains a nested SPLIT function that splits the string on a space delimiter.

SPLIT(InvoiceDate, " ")[0] –> Drops the time from the string and leaves the date intact. Then, we split that value on the forward slash delimiter.

Kubernetes command line

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Kubernetes provides a powerful command-line interface (CLI) called kubectl that allows you to interact with Kubernetes clusters. Here are some commonly used kubectl commands:

Cluster Information:

  1. View Cluster Information:kubectl cluster-info
  2. Display Nodes:kubectl get nodes

Pods:

  1. List Pods:kubectl get pods
  2. Pod Details:kubectl describe pod <pod_name>
  3. Create Pod:kubectl apply -f pod.yaml

Deployments:

  1. List Deployments:kubectl get deployments
  2. Scale Deployment:kubectl scale deployment <deployment_name> --replicas=3
  3. Rollout History:kubectl rollout history deployment <deployment_name>

Services:

  1. List Services:kubectl get services
  2. Service Details:kubectl describe service <service_name>

ConfigMaps and Secrets:

  1. List ConfigMaps:kubectl get configmaps
  2. List Secrets:kubectl get secrets

Logs and Exec:

  1. Pod Logs:kubectl logs <pod_name>
  2. Run Command in Pod:kubectl exec -it <pod_name> -- /bin/sh

Namespaces:

  1. List Namespaces:kubectl get namespaces
  2. Switch Namespace:kubectl config set-context --current --namespace=<namespace_name>

Contexts and Configuration:

  1. List Contexts:kubectl config get-contexts
  2. Switch Context:kubectl config use-context <context_name>

Deleting Resources:

  1. Delete Pod:kubectl delete pod <pod_name>
  2. Delete Deployment:kubectl delete deployment <deployment_name>
  3. Delete Service:kubectl delete service <service_name>

More Resources:

Remember to replace <pod_name>, <deployment_name>, <service_name>, etc., with the actual names of your Kubernetes resources.

These are just a few examples, and kubectl provides a wide range of commands for managing various aspects of Kubernetes clusters. Always refer to the official Kubernetes documentation for detailed information and options.

Linux: Increasing the size of a file system on Linux

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Increasing the size of a file system on Linux that is managed by Logical Volume Manager (LVM) involves several steps. Here’s a general guide assuming you’re working with an LVM-managed file system:

Steps to Increase File System Size Using LVM:

1. Check Current Disk Space:

df -h

2. Check LVM Configuration:

sudo vgdisplay # List volume groups sudo lvdisplay # List logical volumes

3. Extend the Logical Volume:

  • Identify the logical volume (LV) associated with the file system you want to extend.

sudo lvextend -l +100%FREE /dev/vg_name/lv_name

Replace vg_name with your volume group name and lv_name with your logical volume name.

4. Resize the File System:

  • Resize the file system to use the new space.
    • For ext4:bashCopy codesudo resize2fs /dev/vg_name/lv_name
    • For XFS:bashCopy codesudo xfs_growfs /mount_point

Replace /mount_point with the actual mount point of your file system.

5. Verify the Changes:

df -h

That’s it! You’ve successfully increased the size of your file system using LVM. Make sure to replace vg_name and lv_name with your specific volume group and logical volume names.

Example:

Let’s assume you have a volume group named vg_data and a logical volume named lv_data that you want to extend.

# Check current disk space df -h # Check LVM configuration sudo vgdisplay sudo lvdisplay # Extend the logical volume sudo lvextend -l +100%FREE /dev/vg_data/lv_data # Resize the ext4 file system sudo resize2fs /dev/vg_data/lv_data # Verify the changes df -h

Make sure to adapt the commands based on your specific volume group and logical volume names, as well as the file system type you are using. Always perform these operations with caution and have backups available, especially when dealing with critical data.

Linux: Sharing a command line terminal

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Sharing a command line terminal on Linux can be done using various tools and methods. Below are a few common ways to share a terminal session:

  1. tmux (Terminal Multiplexer):
    • Install tmux if it’s not already installed:sudo apt-get install tmux # On Debian/Ubuntu sudo yum install tmux # On CentOS/RHEL
    • Start a tmux session:tmux
    • Run your commands inside the tmux session.
    • To detach from the session (leave it running in the background), press Ctrl-b followed by d.
    • To reattach to the session later:tmux attach
  2. screen:
    • Install screen if it’s not already installed:sudo apt-get install screen # On Debian/Ubuntu sudo yum install screen # On CentOS/RHEL
    • Start a screen session:screen
    • Run your commands inside the screen session.
    • To detach from the session, press Ctrl-a followed by d.
    • To reattach to the session later:bashCopy codescreen -r
  3. SSH (Secure Shell):
    • You can use SSH to connect to another machine and share a terminal.
    • On the machine you want to access:ssh user@remote_ip
    • Run your commands in the SSH session.
  4. Tmuxp:
    • tmuxp is a session manager for tmux that allows you to save and load tmux sessions easily.
    • Install tmuxp:bashCopy codepip install tmuxp
    • Create a tmuxp configuration file (~/.tmuxp/config.yaml) to define your session.
    • Start a session using:tmuxp load session_name
    Replace session_name with the name of your configuration file.

Choose the method that best fits your needs and preferences. Each method has its own set of features and benefits, so you might want to explore them further based on your use case.

IBM MQ Series main command line

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IBM MQ Series, now known simply as IBM MQ, is a messaging middleware that allows applications to communicate with each other. Administration of IBM MQ involves using various commands to manage queues, topics, channels, and other aspects of the messaging system. Here are some of the main IBM MQ administration commands:

  1. Display Queue Manager Information: dspmqinf
  2. Create Queue Manage: crtmqm
  3. Start Queue Manager: strmqm <QueueManagerName>
  4. Stop Queue Manager: endmqm <QueueManagerName>
  5. Display List of Queue Managers: dspmq
  6. Display Queues: dspmq -m <QueueManagerName>
  7. Create Local Queue: runmqsc <QueueManagerName> Inside the runmqsc console: define qlocal(<QueueName>) end
  8. Create Remote Queue: runmqsc <QueueManagerName> Inside the runmqsc console:define qremote(<QueueName>) RNAME('<RemoteQueueManager>') XMITQ('<TransmissionQueue>') end
  9. Display Channels: dis chl(<ChannelName>)
  10. Start Channel: start chl(<ChannelName>)
  11. Stop Channel: stop chl(<ChannelName>)
  12. Display Listeners: dis listener(<ListenerName>)
  13. Start Listener: start listener(<ListenerName>)
  14. Stop Listener: stop listener(<ListenerName>)
  15. Display Topic Information: dis topic(<TopicName>)
  16. Create Topic Object: runmqsc <QueueManagerName> Inside the runmqsc console: define topic(<TopicName>) topicstr('<TopicString>') end

These commands are a subset of the many commands available for IBM MQ administration. Always refer to the official IBM MQ documentation for the most up-to-date and comprehensive information on IBM MQ administration commands and practices.

PostgreSQL: COPY command is used to import data from a file into a table

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In PostgreSQL, the COPY command is used to import data from a file into a table. If you want to use the COPY command to import data into a table named track_raw, you can follow these steps:

  1. Prepare your data file: Ensure that you have a data file (e.g., a CSV file) containing the data you want to import. Make sure that the data in the file matches the structure of the track_raw table in your PostgreSQL database.
  2. Place the data file in a location accessible to the PostgreSQL server: The data file should be located in a directory that PostgreSQL has read access to.
  3. Use the COPY command: You can run the COPY command from the PostgreSQL command-line client (psql) or in SQL scripts. The basic syntax of the COPY command for importing data is as follows:COPY table_name FROM 'file_path' [WITH (options)];
    • table_name: The name of the table where you want to import data (track_raw in your case).file_path: The full path to the data file you want to import.options: This is an optional clause where you can specify additional options, such as the delimiter, CSV header, and more.
    For example, if your data file is named “data.csv” and located in the /path/to/data/ directory, and it’s a CSV file with a header row, you can use the following command:COPY track_raw FROM '/path/to/data/data.csv' WITH CSV HEADER; The CSV format and HEADER option indicate that the file is in CSV format with a header row.
  4. Grant necessary privileges: Ensure that the PostgreSQL user executing the COPY command has the necessary privileges on the track_raw table and the file’s directory.
  5. Verify the data: After running the COPY command, you can verify the imported data by querying the track_raw table. For example:SELECT * FROM track_raw; This query will display the imported data.

Remember that the PostgreSQL server must have read access to the data file, and the PostgreSQL user executing the COPY command must have the appropriate privileges on the table. Additionally, ensure that the data file’s format (e.g., CSV) and the table’s structure match to avoid data import issues.

Linux: How to display ‘cpu’ information on Linux

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You can display CPU information on Linux using various commands and tools. Here are some of the most common methods:

  1. lscpu Command: The lscpu command provides detailed information about your CPU, including its architecture, number of cores, threads, and more. Open a terminal and run:lscpu This command will display information about your CPU in a structured format.
  2. /proc/cpuinfo File: The /proc/cpuinfo file contains detailed information about your CPU. You can use the cat command or a text editor to view its contents:cat /proc/cpuinfo This file provides a wealth of information about your CPU, including model, vendor, cores, flags, and more.
  3. top Command: The top command is a dynamic system monitoring tool that displays real-time information about system performance, including CPU usage. Run the following command:top The CPU information is displayed at the top of the output.
  4. htop Command: htop is an interactive process viewer and system monitor. It provides a more user-friendly interface than top and displays CPU information prominently. You may need to install it on some distributions:htop
  5. inxi Command: The inxi command is a versatile tool that provides detailed system information, including CPU details. Install it if it’s not already available on your system and then run:mathematica inxi -C This will display information about your CPU and its characteristics.
  6. Hardinfo (GUI Tool): If you prefer a graphical user interface, you can install a tool like “Hardinfo” to display detailed information about your CPU and other hardware components. Install it with: sudo apt-get install hardinfo # On Debian/Ubuntu After installation, you can run “System Profiler and Benchmark” from your applications menu to access CPU information.
  7. lshw Command: The lshw command is a general-purpose hardware information tool. You can run it to display detailed information about your CPU: sudo lshw -c cpu This command will show information about the CPU, including its product, vendor, and capabilities.

Each of these methods provides different levels of detail and presentation. Choose the one that best suits your needs and your familiarity with the command-line or graphical tools.

Configuring an SMB (Server Message Block) server

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Configuring an SMB (Server Message Block) server on a Linux system allows you to share files and resources with Windows and other SMB/CIFS-compatible clients. Samba is the most popular and widely used software for setting up an SMB server on Linux. Here’s how to configure an SMB server using Samba:

  1. Install Samba:Use your package manager to install the Samba package. On most Linux distributions, you can install it using commands like these:For Debian/Ubuntu-based systems:bashCopy codesudo apt-get update sudo apt-get install samba For Red Hat/CentOS-based systems:sudo yum install samba
  2. Create a Directory to Share:Choose the directory you want to share via SMB. For example, you can create a directory named “smb_share” under /srv:sudo mkdir -p /srv/smb_share
  3. Edit the Samba Configuration File:The Samba configuration file is typically located at /etc/samba/smb.conf. You can edit it using a text editor like nano or vi:bashCopy codesudo nano /etc/samba/smb.conf Add or modify the configuration for your share at the end of the file. Below is a basic example:[myshare] comment = My SMB Share path = /srv/smb_share browseable = yes read only = no valid users = username
    • [myshare]: This is the share name that SMB clients will use to access the shared directory.comment: A short description or comment for the share.path: The path to the directory you want to share.browseable: Indicates whether the share is visible to clients in network browsing.read only: Set to no to allow both read and write access.valid users: List of usernames allowed to access the share (replace “username” with the actual username).
    Adjust the settings according to your requirements.
  4. Create a Samba User:To access the SMB share, you need a Samba user account. Create a Samba user by setting a password for an existing Linux user. Replace “username” with the Linux username you want to use for SMB access:sudo smbpasswd -a username You will be prompted to set a password for the Samba user.
  5. Restart Samba Service:After making changes to the Samba configuration, restart the Samba service to apply the settings:sudo systemctl restart smbd If you’re using a sysvinit-based system, you can use service instead of systemctl.
  6. Configure Firewall (if necessary):If you have a firewall enabled, make sure to allow SMB traffic. Samba uses ports 139 and 445 for communication. The exact configuration depends on your firewall software.
  7. Access the SMB Share:You can access the shared directory from a Windows or other SMB client using \\<server_name_or_ip>\<share_name> (e.g., \\your_server_ip\myshare). You’ll be prompted to enter the username and password for the Samba user you created.

Your Linux system is now configured as an SMB server, allowing you to share files and directories with Windows and other SMB clients. Customize the Samba configuration to meet your specific needs, such as authentication methods, permissions, and share options.