myline.de: new one-liners

Copy a directory with its contents

Sat, 10 Oct 2026 00:00:00 GMT

Copies a folder recursively with cp -a. Permissions, owner, timestamps and symlinks are preserved. $ cp -a -- /var/www/vhosts/example.com/httpdocs/wp-content/themes/mytheme /var/www/vhosts/example.com/httpdocs/wp-content/themes/mytheme-copy

Copy a file

Sat, 10 Oct 2026 00:00:00 GMT

Copies a file with cp, keeps permissions and timestamps and asks before overwriting. $ cp -ip -- /var/www/vhosts/example.com/httpdocs/.htaccess /var/www/vhosts/example.com/private/htaccess-copy

Create a dated backup copy of a file

Sat, 10 Oct 2026 00:00:00 GMT

Quickly creates a copy with date and time in its name before a change, for example .htaccess.bak-2026-10-10-1430. $ cp -p -- /var/www/vhosts/example.com/httpdocs/.htaccess /var/www/vhosts/example.com/httpdocs/.htaccess.bak-$(date +%F-%H%M)

Create a directory including parent folders

Sat, 10 Oct 2026 00:00:00 GMT

Creates a directory and any missing parent folders automatically. No error if it already exists. $ mkdir -p -- /var/www/vhosts/example.com/private/backups/2026

Create or repoint a symbolic link

Sat, 10 Oct 2026 00:00:00 GMT

Creates a symlink or points an existing one to a new target, typical for release directories. $ ln -sfn -- /var/www/vhosts/example.com/releases/2026-10-10 /var/www/vhosts/example.com/current

Delete a directory with all its contents

Sat, 10 Oct 2026 00:00:00 GMT

Deletes a folder including subfolders and files. -I asks once before starting. $ rm -rI -- /var/www/vhosts/example.com/httpdocs/old

Delete a file

Sat, 10 Oct 2026 00:00:00 GMT

Deletes a single file with rm and asks first. Deleted files do not go to a trash bin. $ rm -i -- /var/www/vhosts/example.com/httpdocs/old.zip

Empty a file without deleting it

Sat, 10 Oct 2026 00:00:00 GMT

Truncates a file to 0 bytes while keeping name, permissions and open file handles. Typical for oversized log files. $ truncate -s 0 -- /var/www/vhosts/example.com/logs/error_log

Extract a ZIP archive into a directory

Sat, 10 Oct 2026 00:00:00 GMT

Extracts a ZIP file into its own target folder instead of dumping the contents into the current directory. $ unzip -q /var/www/vhosts/example.com/private/upload.zip -d /var/www/vhosts/example.com/private/upload

Find a file by name

Sat, 10 Oct 2026 00:00:00 GMT

Finds files and folders whose name contains a search term, ignoring upper and lower case. $ find /var/www/vhosts -iname '*wp-config*' 2>/dev/null

List directory contents with permissions and sizes

Sat, 10 Oct 2026 00:00:00 GMT

Lists all files in a folder including hidden files with permissions, owner, size and date. $ ls -lAh --group-directories-first -- /var/www/vhosts/example.com/httpdocs

Move a file to another directory

Sat, 10 Oct 2026 00:00:00 GMT

Moves a file or directory into another folder with mv and asks before overwriting. $ mv -i -- /var/www/vhosts/example.com/httpdocs/old.zip /var/www/vhosts/example.com/private/

Pack a directory into a ZIP archive

Sat, 10 Oct 2026 00:00:00 GMT

Packs a folder recursively into a ZIP file, for example to hand a website over to someone. $ cd /var/www/vhosts/example.com && zip -rq /var/www/vhosts/example.com/private/httpdocs.zip httpdocs

Recursively delete all files with a given name

Sat, 10 Oct 2026 00:00:00 GMT

Searches all subfolders for files matching a name or pattern and deletes them, for example scattered error_log files. $ find /var/www/vhosts/example.com/httpdocs -type f -name 'error_log' -print -delete

Rename a file or directory

Sat, 10 Oct 2026 00:00:00 GMT

Renames a file or directory with mv and asks before overwriting an existing file. $ mv -i -- /var/www/vhosts/example.com/httpdocs/index.html /var/www/vhosts/example.com/httpdocs/index.html.old

Rename many files at once

Sat, 10 Oct 2026 00:00:00 GMT

Renames multiple files with a regular expression, for example all .jpeg to .jpg. With -n it only shows a preview first. $ rename -n 's/\.jpeg$/.jpg/' *.jpeg

Securely overwrite and delete a file

Sat, 10 Oct 2026 00:00:00 GMT

Overwrites a file several times with random data and then deletes it, for example an old database dump. $ shred -u -z -n 3 -- /root/old-dump.sql

Add a cron job that logs its output

Fri, 09 Oct 2026 00:00:00 GMT

Adds a job to your own crontab whose output and error messages are written to a log file. $ (crontab -l 2>/dev/null; echo "*/15 * * * * /usr/bin/php /var/www/vhosts/example.com/httpdocs/wp-cron.php >> /var/www/vhosts/example.com/logs/wp-cron.log 2>&1") | crontab -

Add an IP address to an nftables blocklist

Fri, 09 Oct 2026 00:00:00 GMT

Add an address or network to an existing nftables set so the drop rule takes effect immediately. $ nft add element inet filter blocklist '{ 203.0.113.25 }'

Align output as a table with column

Fri, 09 Oct 2026 00:00:00 GMT

Aligns delimited text into clean columns, for example /etc/passwd, CSV files or the output of mount. $ column -t -s ':' /etc/passwd

Allow a port only from a specific IP with ufw

Fri, 09 Oct 2026 00:00:00 GMT

Restrict access to a port such as SSH or 8443 to a single IP address or subnet. $ ufw allow from 198.51.100.0/24 to any port 22 proto tcp

Analyze boot time and find slow services

Fri, 09 Oct 2026 00:00:00 GMT

Shows the total duration of the last system boot and the 20 services that took the longest to start. $ systemd-analyze && systemd-analyze blame --no-pager | head -20

Analyze disk usage interactively with ncdu

Fri, 09 Oct 2026 00:00:00 GMT

Scan a directory and show its usage as a navigable list in the terminal. More convenient than du for finding space hogs. $ ncdu -x /var

Analyze Googlebot requests in the access log

Fri, 09 Oct 2026 00:00:00 GMT

Shows which URLs Googlebot fetches most often according to the access log. Helps with crawl budget and indexing questions. $ grep -i "googlebot" /var/www/vhosts/system/example.com/logs/access_ssl_log | awk '{print $7}' | sort | uniq -c | sort -rn | head -20

Analyze server errors (5xx) in the access log

Fri, 09 Oct 2026 00:00:00 GMT

Lists URLs with status codes 500 to 599 along with their count. Shows which scripts crash or run into timeouts. $ awk '$9 ~ /^5[0-9][0-9]$/ {print $9, $7}' /var/www/vhosts/system/example.com/logs/access_ssl_log | sort | uniq -c | sort -rn | head -20

Analyze the network path with mtr

Fri, 09 Oct 2026 00:00:00 GMT

Create a report with packet loss and latency for every hop on the way to a host. $ mtr -rwc 50 example.com

Analyze the slow query log for the slowest queries

Fri, 09 Oct 2026 00:00:00 GMT

Groups similar queries in the slow query log and shows the ten with the highest total runtime. $ mysqldumpslow -s t -t 10 /var/log/mysql/mariadb-slow.log

Back up a Docker volume to a tar archive

Fri, 09 Oct 2026 00:00:00 GMT

Pack the contents of a Docker volume into a tar.gz file on the host using a temporary Alpine container. $ docker run --rm -v app_data:/data:ro -v /root/docker-backup:/backup alpine tar czf /backup/app_data.tar.gz -C /data .

Back up a single database consistently as gzip

Fri, 09 Oct 2026 00:00:00 GMT

Exports a database while it is in use, without table locks, and compresses the dump with gzip. $ mysqldump --single-transaction --quick -u dbuser -p wp_example | gzip > /var/www/vhosts/example.com/wp_example.sql.gz

Back up a single domain with Plesk tools

Fri, 09 Oct 2026 00:00:00 GMT

Uses pleskbackup to back up a domain including files, databases and mail into a single file. $ plesk bin pleskbackup --domains-name example.com --output-file=/root/backup-example.com.tar

Back up all databases into one gzipped file

Fri, 09 Oct 2026 00:00:00 GMT

Backs up every database on the server, including routines and events, into a compressed dump. $ mysqldump --single-transaction --quick --all-databases --routines --events | gzip > /root/all-databases.sql.gz

Back up each database into its own gzipped file

Fri, 09 Oct 2026 00:00:00 GMT

Creates a separate compressed dump for every database on the server. Makes targeted restores easier. $ for db in $(mysql -NBe 'SHOW DATABASES' | grep -Ev '^(information_schema|performance_schema|sys)$'); do mysqldump --single-transaction --quick "$db" | gzip > "/root/db-backup/$db.sql.gz"; done

Back up iptables rules to a file

Fri, 09 Oct 2026 00:00:00 GMT

Save all current IPv4 firewall rules to a timestamped file with iptables-save. $ iptables-save > /root/iptables-$(date +%F-%H%M).rules

Back up the crontab to a dated file

Fri, 09 Oct 2026 00:00:00 GMT

Saves a user's current crontab to a file with the date in its name. A good idea before any change. $ crontab -l > ~/crontab-backup-$(date +%F).txt

Back up the WordPress database as a gzip file

Fri, 09 Oct 2026 00:00:00 GMT

Exports the installation's database and compresses it with gzip on the fly. WP-CLI reads the credentials from wp-config.php. $ wp db export - --path=/var/www/vhosts/example.com/httpdocs | gzip > /var/www/vhosts/example.com/db-backup.sql.gz

Ban an IP address manually in CrowdSec

Fri, 09 Oct 2026 00:00:00 GMT

Add a time-limited ban decision for an IP address or network in CrowdSec. $ cscli decisions add --ip 203.0.113.25 --duration 24h --reason 'manual ban'

Block a single IP address immediately with iptables

Fri, 09 Oct 2026 00:00:00 GMT

Temporarily block an attacking IP address with iptables without touching the rest of the firewall configuration. $ iptables -I INPUT -s 203.0.113.25 -j DROP

Block an IP address or subnet with ufw

Fri, 09 Oct 2026 00:00:00 GMT

Insert a deny rule at the top of the ufw rules so it takes priority over existing allow rules. $ ufw insert 1 deny from 203.0.113.0/24

Calculate the average, minimum and maximum of a column

Fri, 09 Oct 2026 00:00:00 GMT

Uses awk to calculate the mean, smallest and largest value of a column, for response times or file sizes. $ awk -v c=2 'NR == 1 {min = max = $c} {s += $c; if ($c < min) min = $c; if ($c > max) max = $c} END {if (NR) printf "n=%d avg=%.2f min=%s max=%s\n", NR, s/NR, min, max}' measurements.txt

Calculate the total size of all files of one type

Fri, 09 Oct 2026 00:00:00 GMT

Count all files with a given extension and sum up their size. Shows, for example, how much space all videos or logs use. $ find /var/www/vhosts/example.com/httpdocs/wp-content/uploads -type f -iname '*.mp4' -printf '%s\n' | awk '{s+=$1; n++} END {printf "%d Dateien, %.1f MB\n", n, s/1048576}'

Capture network traffic on a port with tcpdump

Fri, 09 Oct 2026 00:00:00 GMT

Show packets for a specific port on all interfaces to check whether requests reach the server. $ tcpdump -i any -nn -c 100 port 25

Change domain: replace the old domain in the database

Fri, 09 Oct 2026 00:00:00 GMT

Backs up the database and replaces the old domain with the new one in all tables. The core step of a migration or domain change. $ wp db export /var/www/vhosts/example.com/before-domain-change.sql --path=/var/www/vhosts/example.com/httpdocs && wp search-replace '//old.example.com' '//example.com' --all-tables --skip-columns=guid --path=/var/www/vhosts/example.com/httpdocs

Change or set the passphrase of an SSH key

Fri, 09 Oct 2026 00:00:00 GMT

Change the passphrase of an existing private key without having to generate a new key. $ ssh-keygen -p -f ~/.ssh/id_ed25519_server

Change service settings with an override

Fri, 09 Oct 2026 00:00:00 GMT

Opens an editor for a drop-in file that changes a service's settings without touching the original unit file. $ systemctl edit mariadb

Change swappiness at runtime

Fri, 09 Oct 2026 00:00:00 GMT

Sets the kernel's swappiness value immediately, without a reboot. Applies until the next reboot unless made permanent. $ sysctl vm.swappiness=10

Change the message of the last commit

Fri, 09 Oct 2026 00:00:00 GMT

Replace the message of the last commit with git commit --amend, including any currently staged changes. $ git commit --amend -m 'Fix: correct cache path in configuration'

Change the password of a Plesk mailbox

Fri, 09 Oct 2026 00:00:00 GMT

Sets a new password for an existing email address in Plesk, for example after an account was compromised. $ plesk bin mail --update info@example.com -passwd 'NewSecurePassword'

Change the PHP version of a domain from the command line

Fri, 09 Oct 2026 00:00:00 GMT

Assigns a different PHP handler to a Plesk domain, for example to switch to a newer PHP version. $ plesk bin domain --update example.com -php_handler_id plesk-php83-fpm

Change the restart policy of a Docker container

Fri, 09 Oct 2026 00:00:00 GMT

Set a running container to restart automatically after crashes and reboots without recreating it. $ docker update --restart unless-stopped app

Change the role of a WordPress user

Fri, 09 Oct 2026 00:00:00 GMT

Sets a new role for a user, for example to demote an administrator to editor. $ wp user set-role editorial editor --path=/var/www/vhosts/example.com/httpdocs