Recorded to $ history:
$ command
Not recorded to $ history (has a space before the command):
$  command

Add files to archive file with no compression:
7z a -mx=0 file.zip inputfile.txt

AES-256-encrypt file ("-mx=0" is fastest):
7z a -t7z -m0=lzma2 -mx=9 -mfb=64 -md=32m -ms=on -mhe=on -p output.7z file.zip
Basically from
https://askubuntu.com/questions/928275/7z-command-line-with-highest-encryption-aes-256-encrypting-the-filenames
:
"a          Add (dir1 to archive.7z)
-t7z        Use a 7z archive
-m0=lzma2   Use lzma2 method
-mx=9       Use the '9' level of compression = Ultra
-mfb=64     Use number of fast bytes for LZMA = 64
-md=32m     Use a dictionary size = 32 megabytes
-ms=on      Solid archive = on
-mhe=on     7z format only : enables or disables archive header encryption
-p          Add a password"

Recursively 7-pass-shred files in current directory (--verbose shows stdout, so you probably do not want to use that):
find . -type f | xargs -d "\n" shred --force --iterations=7 --remove --zero

Look for symlinks in current directory:
find . -type l

Rename directories in current directory to random hexadecimal numbers (run three or more times if you want):
ls -1A | xargs -d "\n" sh -c 'for arg do devran=$(xxd -ps /dev/random | head -n 1); mv "$arg" "$devran"; done' _

7 characters:
ls -1A | xargs -d "\n" sh -c 'for arg do devran=$(xxd -ps /dev/random | grep -o "^......." | head -n 1); mv "$arg" "$devran"; done' _

Check for any remaining files or symbolic links:
find . -type f
find . -type l

Check if the ".thumbnails" folder has spied on you:
cd /home/ubuntu/.thumbnails/normal
[if you see spyware/spydata, your images saved there as small images, then delete as stated above]

Also check
"/home/ubuntu/.thumbnails/large"
and
"/home/ubuntu/.cache/thumbnails"
for spy data

Check the timestamp on /root/.thumbnails/ via:
sudo stat /root/.thumbnails/

Delete stdout / log nothing:
cls; cd /

View files with Tor Browser only to prevent file explorer programs from making excess files.