linux open file command

The shutdown command of Linux/macOS can be shut down, restarted, and timed operations through parameters. 1. Turn off the machine immediately and use sudoshutdownnow or -h/-P parameters; 2. Use the time or specific time point for the shutdown, cancel the use of -c; 3. Use the -r parameters to restart, support timed restart; 4. Pay attention to the need for sudo permissions, be cautious in remote operation, and avoid data loss.

The steps to configure an NTP server include installing services, modifying configuration files, checking synchronization status, and setting up a firewall. 1. Install NTP service: Use sudoapt on Ubuntu/Debian, use sudoyum to install on CentOS/RHEL, start and enable the service after installation; 2. Modify the configuration file /etc/ntp.conf: Add trusted upstream servers such as serverntp.aliyun.comiburst and servertime.windows.comiburst, and set allow access to network segments such as restrict192.168.1.0mask255.255.255.0nomod

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.

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

Encrypted files on Linux can be implemented in many ways, the key is to choose the right tool. 1. Use GPG to quickly encrypt a single file, support symmetric and asymmetric encryption, suitable for temporary protection of files; 2. eCryptfs is suitable for encrypting the entire directory, and automatically encrypted by mounting encrypted folders, suitable for protecting user private data; 3. Create an encrypted container, combining dd, lostup and cryptsetup tools to create an encrypted space similar to TrueCrypt, suitable for storing sensitive information for a long time. Each method is suitable for different scenarios. When using it, you should pay attention to saving passwords and keys to avoid data loss.

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