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How to install and secure Nginx web server on Linux? (SSL Configuration)
NginxfailstostartafterSSLconfigduetosyntaxerrors,incorrectfilepaths,orrestrictivepermissions—notencryptionitself;alwaysrunsudonginx-tfirst,usefullchain.pem,setprivkey.pemto600,andplacessl_trusted_certificateinthehttpblock.
Mar 04, 2026 am 12:20 AM
How to mount and unmount external drives in Linux? (Filesystem Management)
To manually mount/unmount a USB flash drive or mobile hard disk using mount and umount, you must first use lsblk to confirm the device name (such as /dev/sdb1), create an empty mount point (such as /mnt/usb), and specify the file system type (vfat/ntfs3/ext4) for mounting. Before unmounting, make sure that no processes are occupied. You can use lsof or fuser to kill it to avoid using lazyunmount.
Mar 03, 2026 am 01:21 AM
How to check memory usage and clear RAM cache in Linux?
It is normal for available to be smaller than used, because Linux uses free memory for pagecache and slab to improve performance, and available is the real memory that can be allocated immediately; high buff/cache does not indicate a problem, but is the norm.
Mar 03, 2026 am 12:44 AM
How to check Linux kernel version and perform upgrades?
When checking the kernel version, you need to confirm the running, installed and upgradeable versions at the same time. After the upgrade, you must update the GRUB default items and rebuild the initramfs. Otherwise, the restart may fail or the old kernel may still be enabled.
Mar 02, 2026 am 12:17 AM
How to generate and install Let's Encrypt SSL certificates on Linux?
The main reason for the failure of the certbot command is an installation error or a confusing Python environment. Snap installation should be used first; the failure of nginxreload is usually due to an incorrect certificate path or insufficient permissions; automatic renewal requires the explicit addition of the --deploy-hook reload service; the pan-domain name certificate must be verified with DNS-01.
Mar 02, 2026 am 12:10 AM
How to compress and extract archive files in Linux? (Tar & Gzip)
By default, tar only packs but does not compress. To enable gzip compression, you need to explicitly add -z (such as tar-czf). You must also use -xzf to decompress .tar.gz. Confusing packaging and compression, and missing -z are common sources of errors.
Mar 01, 2026 am 01:50 AM
How to create a bootable USB drive using Linux command line? (dd command)
You must confirm the device name before executing dd, otherwise the system disk will be bricked by mistake; unplug other USB devices before operation, use lsblk-d-oNAME, MODEL, SIZE, TRAN to filter device names whose TRAN is USB and SIZE matches (such as sdb), clear the signature, verify the hash, use the bs=4M/status=progress/oflag=sync parameter correctly, and execute sync&&eject after writing to ensure the disk is dropped.
Mar 01, 2026 am 01:25 AM
How to automate server backups using Rsync in Linux?
Without --delete, rsync will not delete redundant files on the target side and will only copy in one direction; add --delete to mirror the source directory (it is recommended to --dry-run first), or use --delete-after to be safer; to clean up old backups, use find instead of relying on rsync.
Feb 28, 2026 am 12:40 AM
How to manage system services using Systemd in Linux? (Systemctl)
Systemctlstatus displays inactive (dead) because the service has not been started and is not a fault; it needs to be started or enabled and daemon-reloaded before it takes effect. Pay attention to the Active line and journalctl log.
Feb 28, 2026 am 12:17 AM
How to install and configure Fail2Ban to protect Linux SSH?
After Fail2Ban is installed, the status reports "Nofilefound" because no jail is enabled by default. You need to create /etc/fail2ban/jail.local and explicitly set enabled=true, correctly configure the logpath to match the system log path (for example, Debian system uses /var/log/auth.log), and ensure that the filter regular expression can match the SSH failure log line.
Feb 27, 2026 am 12:10 AM
How to manage Git repositories on a Linux server?
To initialize a Git bare warehouse on a Linux server, you must use gitinit--bare/var/repo/project.git, set chown-Rgit:git ownership, configure git-shell to restrict SSH users to only execute Git commands, and strictly verify authorized_keys permissions and SELinux context.
Feb 27, 2026 am 12:06 AM
How to test internet connection speed from Linux terminal? (Speedtest-cli)
The main reason for the failure of speedtest-cli installation is that pip is not pre-installed in the system or the permissions/environment are inconsistent; Ubuntu/Debian needs aptinstallpython3-pip first, CentOS/RHEL8 Use dnfinstallpython3-pip; pip3install--userspeedtest-cli and configure PATH are recommended; lags are often caused by IPv6 issues, which can be solved by adding --ipv4; speed measurement is not allowed due to accidental uploading by default, single thread and no concurrency, so --upload and --multiple should be added; absolute paths or PATH declarations are required in cron; it is recommended to use --json instead of --c for logs
Feb 26, 2026 am 12:44 AM
How to permanently disable IPv6 on Linux systems?
IPv6 disabling requires three layers: kernel parameters, network services (systemd-networkd/NetworkManager), and user space. Only changing sysctl is ineffective. Network services must be configured simultaneously and the corresponding services must be restarted. Otherwise, addresses such as fe80:: will still appear.
Feb 26, 2026 am 12:10 AM
How to troubleshoot DNS resolution issues in Linux servers?
nslookup returns servercan'tfind but dig is normal. This is usually because nslookup uses the nameserver in /etc/resolv.conf (such as 127.0.0.53) by default, while dig uses the local recursive resolver or explicit server by default. If the nameserver is not running, the port is blocked, or does not respond to non-local queries, it will fail. You need to check resolv.conf, systemd-resolved status, nsswitch.conf configuration and network layer connectivity.
Feb 25, 2026 am 02:23 AM
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