Stefan Hornburg (Racke)
Linux Utils Cheatsheet
Remove files by modification date
Move old files to another directory
Copy files instead of symlinks
Sync only files with a certain extension from one directory tree to another
Reduce file size of a JPG image
Combine images into a PDF file
Convert SVG file to PNG with transparency
Finding files with find
Remove files by modification date
This example shows how to remove all files with a modification date before 2016:
find -type f -not -newermt 20160101 | xargs rm
Move old files to another directory
This example shows how to move a large number of files to another directory:
find /var/www/userpics -name '*.jpg' -mtime +31 -print0 | xargs --null mv --target-directory=/backup/oldpics/
Find files by permission
Exact permission (read,write,execute for owner only):
find -perm 700
Find large files
$ du -sh -t 20M $(find /tmp/ -type f) 30M /tmp/OF0dXjBgX3/0207.zip 56M /tmp/lYZNO1PD09/0703.zip 29M /tmp/aF_jPhgvwD/0307.zip
Use ncdu
ncdu
: NCurses Disk Usage
Use cat
Show file contents
$ cat /etc/os-release PRETTY_NAME="Debian GNU/Linux 11 (bullseye)" NAME="Debian GNU/Linux" VERSION_ID="11" VERSION="11 (bullseye)" VERSION_CODENAME=bullseye ID=debian HOME_URL="https://www.debian.org/" SUPPORT_URL="https://www.debian.org/support" BUG_REPORT_URL="https://bugs.debian.org/"
This file should be present on any modern Linux distribution.
Show whitespace
$ cat -vet
Use tail
Show file content without the first line:
$ tail -n +2 test.csv
Use sed
Remove lines from output
Remove single line:
$ sed '1d' file
Remove range of lines:
$ sed '1,5d' file
Extract lines
Extract a single line for a file:
$ sed '123q;d' file
The q
stops processing the file when the line is reached.
If you want to see a couple of lines from a CSV alongside with the header:
$ sed -n -e '1p' -e '809,820p' my.csv
Sort lines with sort
Sort by a column:
~# sort -k 1 myfile
Sort numeric:
~# sort -n myfile
Sort reverse:
~# sort -r myfile
Using date
Display date a month ago:
~# date -d "-1 month" +%Y-%m-%d
It automatically adjusts the day if the resulting date would be invalid.
Set time:
~# date +%T -s "12:12:00"
Epoch
Display epoch
$ date +"%s" 1626247585
Convert epoch to a date
$ date -d @1626247585 Wed 14 Jul 09:26:25 CEST 2021
Using rsync
Copy files instead of symlinks
rsync -L /etc/letsencrypt/live/wildcard.linuxia.de/*.pem root@extern.linuxia.de:/etc/letsencrypt/live/wildcard.linuxia.de/.
Sync only files with a certain extension from one directory tree to another
rsync -av --include="*/" --include='*.status' --exclude='*' /samba/. .
Using ip
Show network interfaces
$ ip -a
Add IP address
$ sudo ip a add 192.168.36.11/24 dev eth0
IPv6
Show global reachable addresses:
$ ip -6 addr show scope global
Using lsof
Open files
Show open files in a directory:
$ lsof /mnt/backup ...
Network connections
$ lsof -i :80 COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME nginx 431729 root 6u IPv4 7170923 0t0 TCP *:http (LISTEN) nginx 431729 root 7u IPv6 7170924 0t0 TCP *:http (LISTEN) nginx 431730 www-data 6u IPv4 7170923 0t0 TCP *:http (LISTEN) nginx 431730 www-data 7u IPv6 7170924 0t0 TCP *:http (LISTEN)
It works with service as well, e.g. lsof -i:ntp
.
See also
Using ncat
Retrieve CheckMK agent output:
$ ncat agent.example.org 6556 < /dev/null
Using lftp
Mirroring
Mirror from remote FTP server to local server
mirror -c source target
Please note that doesn't mirror dot files like .htaccess
.
To include these, adjust the default listing options:
set ftp:list-options -a
SSL
In case you really need to disable SSL (not recommended), use the following command:
set ftp:ssl-allow false
Using curl
Display the headers:
$ curl --head https://example.org
Skip certificate check:
# Shortcut: -k $ curl --insecure https://example.org
Connect without DNS:
$ curl https://example.org --connect-to example.org:93.184.216.34
Using wget
Display the headers:
$ wget --server-response https://example.org
Using convert
Reduce file size of a JPG image
$ convert photo-large.jpg -quality 82 photo-small.jpg
Rotate image clockwise
$ convert image.jpg -rotate 90 image2.jpg
Combine images into a PDF file
$ convert 20220518_1450*.jpg photos.pdf
Convert SVG file to PNG with transparency
$ convert -background none image.svg image.png
Using pdfjam
Produce PDF from image and convert to A4 format:
$ convert image.jpg image.pdf $ pdfjam --paper a4paper --outfile image-a4.pdf image.pdf
Using zip
Create password protected archive
$ zip -e sccl2.zip sccl2_2.9-4_all.deb sccl2-2.9-4.noarch.rpm Enter password: Verify password: adding: sccl2_2.9-4_all.deb (deflated 0%) adding: sccl2-2.9-4.noarch.rpm (deflated 26%)
Using timeout
Run dhclient
with a time limit:
$ timeout 10 dhclient -6
Encryption with GnuPG
Environment variables
GNUPGHOME
Select alternative home directory for GPG configuration and keys:
export GNUPGHOME=~/.gnupg-old/