How to check environment variables under Linux?

If you want to know the network connection on your current computer, you can view it through the command line tool; use netstat-ano on Windows to view all connections and PIDs, use ss-tulnp and lsof-i-P to obtain detailed information, and can also be monitored in real time through graphical interface tools such as resource monitor, nethogs, etc.

To create an LVM volume group, you must first prepare a physical volume (PV) and then create a VG. 1. Use pvcreate to initialize the hard disk or partition into PV, such as pvcreate/dev/sdb1; 2. Use the vgcreate command to combine one or more PVs into VG, such as vgcreatemy_volume_group/dev/sdb1/dev/sdc1; 3. You can customize the PE size through the -s parameter and use vgdisplay to view information; 4. You can dynamically expand VG in the future and add a new PV using vgextend; 5. Before deleting VG, you must confirm that there is no LV and delete it with vgremove.

The steps to configure an NFS server are as follows: 1. Install the nfs-utils or nfs-kernel-server package; 2. Start and enable nfs-server and related RPC services; 3. Edit /etc/exports to configure shared directories and permissions, such as rw, ro, sync, etc.; 4. Execute exportfs-a and open the firewall port; 5. The client uses the mount command to mount or configure fstab to achieve automatic mount; Common problems include permission control, ID mapping, RPC service not being started and configuration not being refreshed, and needs to be checked in conjunction with logs.

The key to managing environment variables is to use .env files to centrally manage, distinguish different environment configurations, inject variables during deployment, and avoid hard-coded sensitive information. Specific practices include: 1. Use .env files to store variables and distinguish them by environment, such as .env.development and .env.production, and add .gitignore; 2. Use NODE_ENV and other identifiers to determine the corresponding configuration of the current environment to automatically load; 3. Inject variables at the system level when deploying servers, Docker or cloud platforms to improve security; 4. All sensitive information must be obtained from environment variables, the naming must be clear, and can be managed in combination with encryption means or special tools.

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

Linux monitoring involves a variety of tools, system performance monitoring tools include top/htop real-time viewing of resource usage, vmstat displays virtual memory status, iostat detects disk IO bottlenecks, and sar records historical performance data. The log monitoring tool includes journalctl filtering service logs, dmesg debugging kernel issues, logrotate management log life cycle, and rsyslog/syslog-ng centralized forwarding logs. In terms of network monitoring, SS/NNSTAT checks the connection status, NMap scans open ports, TCPDump captures traffic analysis, and iftop monitors bandwidth usage. Remote monitoring solutions such as Nagios implement deep custom alarms, Zab

The method of changing the system hostname varies from operating system to operating system, but the overall process is simple and clear. First, check the current host name, which can be viewed through the hostname or hostnamectl command; second, the hostname can be temporarily changed, Linux uses sudohostnamenew-hostname, and macOS uses sudoscutil-setHostNamenew-hostname; if you need to change it permanently, Linux needs to edit the /etc/hostname file and update the old hostname in /etc/hosts to the new name, and then run sudohostname-F/etc/hostname or restart to apply the changes; macO

To troubleshoot VLAN problems, you should first confirm whether the configuration is correct, and then check the interface status, cross-device communication path, and STP and ACL impacts in turn. 1. Use showvlanbrief to confirm whether the VLAN exists and the port is correct, and whether the Trunk port allows the corresponding VLAN to pass; 2. Use showinterfacesstatus and showrunning-configinterface to check whether the interface status is up and mode configuration; 3. Verify whether the connection between switches is Trunk and allows the same VLAN, and whether the configuration of the subinterface of the layer three device is accurate; 4. Check whether the STP status of the port is blocked, and check whether the ACL or private VLAN limits traffic. Click this logic