How to uninstall software on ubuntu?

If you want to know which process is listening for a certain port, you can use the following methods: 1. Use netstat and tasklist to search in Windows; 2. Use lsof or netstat commands in Linux; 3. Use lsof or netstat for macOS. The specific operation is: use netstat-ano|findstr: to obtain the PID in Windows, and then use tasklist|findstr to check the process; use lsof-i: or netstat-tulnp|grep: to Linux; macOS is similar to Linux, and can use lsof-i: or netstat-anptcp|grep: to check the process. These

1. Use --since and --until to define the time range, such as journalctl--since"1 hour ago"--until"now"; 2. Filter specific service logs through -u specifying units, such as journalctl-unginx.service; 3. Use -p to filter by priority, such as journalctl-perr only displays error level logs; 4. Combine multiple filtering conditions to achieve accurate query, such as journalctl-usshd.service--since"2 hour ago"-perr. Master these methods

Running a Docker container requires mastering several basic commands and processes. 1. Preparation: Confirm the local image exists, view it through dockerimages, and use dockerpull to pull it; 2. The simplest way to run: use dockerrun command, such as dockerrun-namemy-nginx-d-p8080:80nginx to start the container; 3. View and manage containers: use dockerps to view the running status, dockerstop, dockerstart and dockerrm are used to stop, start and delete containers respectively; 4. Advanced settings: realize data persistence through the -v mount directory, and use -e to set environment variables, such as d

Mastering the commonly used commands and formats of sed is the key to efficient text processing. 1. Replace text: Use s/original content/new content/grammar, add g to achieve global replacement, and other symbols such as # can be used as delimiters; 2. Delete content: Delete the specified line or the line matching keywords through the d command, and support scope deletion; 3. Insert and append: Use i to insert before a certain line, and use a to add content after a certain line; note that the default operation does not modify the original file, and the -i parameter must be added before the change is saved.

When writing ansibleplaybook, you need to clarify the goals and structure. 1. Master the basic structure: including hosts, tasks, become, vars and other elements; 2. Use modules to execute tasks: such as apt, copy, service, etc., and pay attention to parameter integrity and idempotence; 3. Use variables and conditions to judge: define variables through vars, and control execution conditions in combination; 4. Pay attention to format and testing: Ensure that the YAML format is correct, use --check for testing and use the ad-hoc command to verify the behavior of the module.

The key to configuring a security group and firewall for cloud instances is to understand the traffic control logic and follow the principle of least permissions. 1. The security group is equivalent to a virtual firewall. It is used to control network traffic in and out of the instance. Only the necessary ports should be opened and the source IP should be restricted; 2. When setting inbound rules, SSH should be restricted to specific IPs. HTTP/HTTPS can be opened to the external network or whitelisted, and the database ports should not be opened to the external network; 3. Outbound rules allow all by default. In the initial stage, it is recommended to keep the default, and gradually tighten it in the future to avoid affecting system updates and service access; 4. Frequently asked questions to check the security group binding, rule configuration, source IP restrictions, network ACL and internal system firewalls, and note that some platforms need to restart the instance after modification. Mastering these key points can effectively improve

There are three main ways to achieve automatic mount in Linux: First, use /etc/fstab to manually configure the mount point, which is suitable for fixed devices, and you need to edit the fstab file and specify the device with UUID to ensure that the mount point exists; second, use autofs to realize dynamic automatic mount, which is suitable for mounting NFS and other network file systems on demand, and autofs and its sub-configuration files need to be installed and configured; third, for hot-swap devices such as USB flash drives, it is recommended to use udisks2 or select a distribution with a desktop environment to achieve automatic mount.

To use iptables to open the port, first confirm whether it is running. If it is not running, it will be started and set to boot automatically; secondly add rules to the INPUT chain, such as: iptables-AINPUT-ptcp--dport8080-jACCEPT; then save the rules to prevent restart failure, use serviceiptablessave to CentOS/RHEL, install iptables-persistent and save it; finally use iptables-L-n-line-numbers to check whether the rules are effective. Note that if the system uses firewalld or nftables, it needs to use the corresponding work instead.