How to troubleshoot VLAN issues

When you encounter a problem with slow network connection, traceroute can help you locate the bottleneck. It is a command line tool that displays the path through which the data packets pass from your computer to the target server by sending probe packets and recording the response time of each step. How to use it is tracertexample.com under Windows and tracerouteexample.com under macOS/Linux/Unix. In the output result, each line represents an intermediate node, including the number of hops, three round trip times and the corresponding IP or host name; if all hops are *, it may be firewall blocking or network failure. Check the jump with delay burst to determine the location of the problem; combined with multiple domain name tests, you can distinguish between general

CentOS or RHEL systems recommend using yum and dnf management software packages. 1. It is recommended to update the cache first during installation, the commands are sudoyumininstall and sudodnfinstall respectively; 2. You can update yumupdate or dnfupgrade, and you can view the list to be updated; 3. Use yumremove or dnfremove to delete, and dnf can automatically clean up useless dependencies; 4. Query to view the installation status through rpm-qa and rpm-q, and yuminfo/dnfinfo get detailed information. Mastering these operations can help to efficiently maintain the system.

To troubleshoot Kubernetes node problems, follow the steps: 1. Use kubectlgetnodes and describenode to view the node status and detailed information, and pay attention to the exceptions in Conditions; 2. Log in to the node to check whether the kubelet status, logs and container runtime are normal; 3. Check the network connection and firewall settings to ensure that the port communication with APIServer is normal; 4. Check the CNI plug-in status and related logs. Through the above methods, the cause of the problem can be basically located, and the problem can be effectively solved by checking it in order.

When encountering an encrypted file, you must first identify the encryption type and then use the corresponding tool to decrypt it. 1. Confirm the encryption method, such as GPG or OpenSSL encryption, through file extension or file command; 2. To decrypt GPG files with gpg command, you need to enter a password or private key such as gpg-ooutput_file-dencrypted_file.gpg; 3. OpenSSL decryption requires specifying algorithm mode such as opensslaes-256-cbc-d-inencrypted_file.enc-outdecrypted_file; 4. File system encryption, such as eCryptfs, automatically decrypts the compressed package after logging in, you can enter the password to decompress.

Tocompileakernelmodule,firstinstallbuildtoolsandheadersspecifictoyourdistribution.OnDebian-basedsystems,runsudoaptupdateandsudoaptinstallbuild-essentiallinux-headers-$(uname-r);onRedHat-basedsystems,usesudodnfgroupinstall"DevelopmentTools"a

To view firewall rules, you need to select the corresponding method based on the operating system and platform. 1. When using iptables in Linux system, execute sudoiptables-L-n-v or add-x to view detailed rules; if using nftables, use nftlistruleset. 2. Ubuntu's UFW firewall uses sudoufwstatusverbose to view status and rules, or read /etc/ufw/user.rules file. 3. Windows uses the PowerShell command Get-NetFirewallRule to view inbound rules, or browse through the graphical interface management console. 4. Cloud platforms such as AWS in EC

The method of rolling back the system update varies from operating system to different operating system, so you need to operate with caution and backup in advance. For Windows, it can be achieved by "Settings → Update and Security → Windows Update → View Update History → Uninstall Update", but some cumulative updates cannot be uninstalled directly; macOS needs to rely on TimeMachine backup and restore or reinstall old versions, and it is difficult to downgrade; iOS can only be downgraded within a specific signature period, while Android depends on the brand and Bootloader unlock status, and data must be backed up before flashing; Linux users can use snapshots or log rollbacks, but they need to master command line operations. Overall, you should understand the system mechanism in detail and do a good job of data protection before rolling back.

To update Linux system packages, you must first run sudoaptupdate to refresh the source list, otherwise it may cause the installation to fail or the version is too old. 1. Update the software source: execute sudoaptupdate; 2. Upgrade the software package: It is recommended to use sudoaptfull-upgrade to completely upgrade and install new dependencies, but be careful to uninstall conflict packages; 3. Clean useless packages: Use sudoaptautoremove and sudoaptclean to release disk space; in addition, when encountering GPG errors, you should check the key. If you connect to a connection problem, you can try to replace the domestic mirror source. Usually, you can use aptlist-upgradable to view the upgradeable package, or complete it at one time with the command chain.