WELCOME TO THE OLDFOLIO GOPHER SERVER!

COMMAND LINE NOTES

7-ZIP

7za a -mhe=on -p archive-name.7z original-file

a = add to archive
-mhe=on = encrypt headers as well as data
-p = prompt for password

APT

apt-get --no-install-recommends install package-name

CD

To return to the directory that you just left:

cd -

DATE

FreeBSD: Set the date to 5:05 pm, January 21, 2018

date 201801211705
    yyyymmddhhmm

If you only need to change the hours and minutes

date 1705

will change the time to 5:05 pm and leave the date unchanged.

DD

Overwrite with zeroes a 133 byte file:

dd if=/dev/zero of=filename count=1 bs=133

Overwrite with zeroes a 1 MB byte file:

dd if=/dev/zero of=storage-bin count=1K bs=1024

Overwrite with zeroes a 1 GB byte file:

dd status=progress if=/dev/zero of=storage-bin count=1024K bs=1024
dd status=progress if=/dev/zero of=storage-bin count=1M bs=1024

On my home system, /dev/zero can be used to generate a 10G file
in about 45 seconds. By contrast, /dev/urandom will take about
three minutes. Do not even bother with /dev/random.

DIG

Check the mx record for yandex.com at the name server dns1.yandex.net:

dig mx yandex.com @dns1.yandex.net

On Debian-based systems, dig is supplied by the package dnsutils.
On FreeBSD, dig is supplied by the package bind-utils.

DMIDECODE

Displays hardware information. Must be run as root. See this guide:

https://www.howtoforge.com/dmidecode-finding-out-hardware-details-without-opening-the-computer-case

Display memory information:

dmidecode -t memory

DPKG

List installed packages:

dpkg --get-selections

Show the status of package, PACKAGE:

dpkg-query --status PACKAGE

DU

du -h --max-depth=1

DUPLICITY

Backup files in directory "source" to a remote server. The first
time duplicity runs it will do a full backup. Subsequently, it
will do an incremental backup of changes.

duplicity --encrypt-key gpg-key /home/user/source sftp://host//home/user/target

duplicity --encrypt-key gpg-key /home/user/source file:///home/user/local-target

duplicity restore sftp://host//home/user/backup /home/user/local-restore-directory

On incremental backups, some versions of duplicity will return
the following error message related to GnuPG:

Error processing remote manifest

This is a known and benign error message that does not indicate
any failures in the backup.

ELINKS

If you enable one of the color modes, then [shift]-5 will cycle
through the color schemes for that mode.

You can toggle the numbering of hyperlinks with the period "."

EMACS

My Emacs notes have their own page, or they will have once I set
it up.

GNUPG

Encrypt to a specific user/recipient:

gpg -e -r USER file.txt

Create a detached, ascii-enarmored signature specifying which key to use:

gpg -u key-to-use -a --output file.sig --detach-sig file.txt

Create a non-detached, ascii-enarmored signature specifying which key to use:

gpg -u key-to-use --clearsign file.txt

Verify detached signature:

gpg --verify signature.sig signed-file.txt

Export public key:

gpg -a --export {key-identifier} > public-key.asc

Export secret/private key:

gpg -a --export-secret-keys {key-identifier}  > secret-key.asc

If you should ever need to edit your ~/.gnupg/gpg-agent.conf file,
you will need to reload the gpg-agent once you are finished editing.

$ gpg-connect-agent reloadagent /bye

Use extreme caution if you change the gpg-agent to pinentry-curses.
Doing so breaks the graphical version of Emacs, and I have not yet
found a work-around. If you will be working remotely with GnuPG
encrypted files, you may need to set the agent to pinentry-curses.
Otherwise, the gpg-agent will expect a graphical environment --
and fail when one is not present.

HTML ESCAPE SEQUENCES

& will display &
&lt; will display <
&gt; will display >

You might also find this useful;

<p><a href=""></a></p>

LN

ln -s target-file link-name

LOSETUP

# losetup -a # List the status of all loop devices
# losetup /dev/loop0 filename # Associate loop device 0 with file filename
# losetup -d /dev/loop0 # Detach loop device

NAMEBENCH

Send 128 queries to only the nameservers specified:

namebench -q 128 -O 208.67.222.222, 1.1.1.1, 8.8.8.8

NETHACK

Some nethack commands:

@ = toggle autopickup
d = drop
i = open inventory
r = read (as in read a spellbook)
t = throw (as in throw a dagger)
w = wield weapon
f = fire arrows in quiver using wielded bow
Q = place arrows in quiver
S = save your game and exit
P = put on (as in put on a ring)
R = remove (as in remove a ring)
W = wear armor or shield
T = take off armor or shield
Z = cast a spell
^d = bash (as in bash a door)
#chat = talk to another character
#loot = open a container
#force = attempt to open a locked container
#untrap = rescue pet from pit

Possible ~/.nethackrc

OPTIONS=color,time,hilite_pet,menucolors,!autopickup,role=valkyrie,race=human
#OPTIONS=color,time,role=wizard,race=elf,gender=female

RSYNC

rsync -avuP --delete source-directory/ host:/destination-directory

Notice that the source directory HAS a trailing slash, but that
the destination directory does NOT have a trailing slash.

Hetzner storage boxes only recognize relative paths. So, your rsync
command will need to look something like:

rsync -avuP --delete local-directory/ hetzner:./directory
                                            ^
                                    notice the dot

Synchronize a single file:

rsync -avuP source-directory/filename host:/destination-directory/

Notice that when synchronizing a single file a trailing slash *DOES*
follow the destination directory.

SECURE_DELETE (FreeBSD) / SECURE-DELETE (Debian)

Overwrite and delete all files and subdirectories of DIRECTORY

srm -llr DIRECTORY

SMEM

Report chrome or chromium total memory usage:

smem -t -k -c pss -P chrom | tail -n 1

Report opera total memory usage:

smem -t -k -c pss -P opera | tail -n 1

Report yandex browser total memory usage:

smem -t -k -c pss -P yandex_b | tail -n 1

Report yandex disk total memory usage:

smem -t -k -c pss -P yandex-d | tail -n 1

Report vivaldi total memory usage:

smem -t -k -c pss -P vivaldi | tail -n 1


SSHFS

If you install sshfs, you can mount your remote servers
as an ordinary user.

$ sshfs server-nickname:/home/username /local/mountpoint -o uid=1000,gid=1000

To unmount:

$ fusermount -u /local/mountpoint


SYSCTL

Report hardware information on FreeBSD systems:

# sysctl hw.model hw.machine hw.ncpu


TAR

To archive your /etc and /home directories:

# tar cvf /root/etc-home.tar /etc /home

To create an archive that excludes some files in the target:

tar cvf ~/archive.tar --exclude='excluded-directory/*' *

To list the files in an archive:

tar tvf archive.tar

Compression:

bzip2 = j
gzip = z
xz = J

Create an archive with a time stamp in the archive name:

suffix=`date +%F-%H.%M`
tar cvf /home/user/archive-$suffix.tar /path/to/target-directory/


TMUX

Ctrl-b to enter commands

Detach the current session:

Ctrl-b d

Re-attach a previous session:

tmux attach -t 0

where "0" is the name of the previous session.


USERMOD

To change a user's primary login group:

usermod -g primarygroupname username

To add a user to a secondary group:

usermod -a -G secondarygroupname username

Using the -G switch without the -a switch will remove a user from all secondary groups except those specified by the current instance of the -G switch.

VIM

Find each occurrence of 'foo' and replace it with 'bar':

:%s/foo/bar/g

Edit a remote file:

vim scp://[email protected]:22//home/user/filename

or

:e scp://[email protected]:22//home/user/filename

Prompt for an encryption key:

:X

Center text [based on a 75 character-wide line]:

:ce [75]

Set the maximum number of characters on a line to 75

set tw=75

Various editing tasks:

dd delete current line
~ switch case of characters (from CAPITALS to lower case or vice VERSA)
U MAKE ALL SELECTED CHARACTERS CAPITALS/UPPER CASE
u make all selected characters lower case
J join next line to the current one
> indent selected lines
gq apply text formatting to selected region

" specify a register
"+ specify the clipboard
"+y copy to clipboard
"+d cut to clipboard
"+P paste from clipboard before cursor
"+p paste from clipbaord after cursor

Miscellaneous

echo 3 > /proc/sys/vm/drop_caches

Do a searchon "drop_caches" for additional information, including
the differences between echo 1, echo 2, and echo 3.

File Size Comparison

I keep all of my notes in a very large text file. Here is a size
comparison of the notes in different formats (October 2018):

RAW TEXT  2708583 bytes (100.00%)
DOCX      1254433 bytes ( 46.31%)
ODT       1103976 bytes ( 40.76%)
GZ TEXT   1040337 bytes ( 38.41%)
XZ TEXT    796340 bytes ( 29.40%)
BZ2 TEXT   763485 bytes ( 28.19%)

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