- Run sudo without a password (absolutely not recommended)
- Search
- Time and date
- Mount a USB drive
- Encryption
- Create custom functions
- Fonts
- VNC server
- Screen
- Dummy serial and lp ports
- Terminal
- Cron jobs
- Pandoc
- Windows in i3
This is more to check if this is happening rather than actually doing it. Edit /etc/sudoers with sudo visudo and you can add your username
my_username ALL=(ALL) NOPASSWD:ALL
or a group like wheel
%wheeel ALL=(ALL) NOPASSWD:ALL
If the file has been indexed locate filename otherwise find . -name 'filename'
grep -rnw '/path/to/somewhere/' -e 'pattern'
-ror-Ris recursive,-nis line number-wstands for match the whole word.-l(lower-case L) can be added to just give the file name of matching files.
Along with these, --exclude, --include, --exclude-dir flags could be used for efficient searching:
This will only search through those files which have .c or .h extensions:
grep --include=\*.{c,h} -rnw '/path/to/somewhere/' -e "pattern"
This will exclude searching all the files ending with .o extension:
grep --exclude=*.o -rnw '/path/to/somewhere/' -e "pattern"
For directories it's possible to exclude a particular directory(ies) through --exclude-dir parameter. For example, this will exclude the dirs dir1/, dir2/ and all of them matching *.dst/:
grep --exclude-dir={dir1,dir2,*.dst} -rnw '/path/to/somewhere/' -e "pattern"
You can do it without even opening the files
sed -i -- 's/foo/bar/g' file
foois the text you searchbaris the replacement textfileis the file or files in that folder likeREADME.mdor*.mdor*
You have to escape some characters like space and . * ^ $ [ ] \ / with the \ character
:%s/search/replace/g use escape char)\ for escaping /
In my laptop the hardware clock (BIOS clock) is considered by the operating system (arch) as UTC. So it is important to set that appropiately first.
sudo hwclock --show
I travel quite often and I need to adjust the timezone in my computer. I do it with timedatectl
timedatectl status check the current time, date and timezone. The following will appear:
[unix ~]$ timedatectl status
Local time: Fri 2019-11-08 18:42:28 CET
Universal time: Fri 2019-11-08 17:42:28 UTC
RTC time: Fri 2019-11-08 17:42:28
Time zone: Europe/Madrid (CET, +0100)
System clock synchronized: no
NTP service: inactive
RTC in local TZ: notimedatectl list-timezones check the timezones
timedatectl set-timezone zone/subzone Set the timezone
There are many ways to do that, this is the one I use. Start/enable systemd-timesyncd. Add time servers in the config file /etc/systemd/timesyncd.conf
[Time]
NTP=0.arch.pool.ntp.org 1.arch.pool.ntp.org 2.arch.pool.ntp.org 3.arch.pool.ntp.org
FallbackNTP=0.pool.ntp.org 1.pool.ntp.org 2.pool.ntp.org 3.pool.ntp.orgCheck the sync status timedatectl show-timesync --all
With ghostscript gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
You can change the screen option (72 dpi) to ebook (150 dpi), prepress (300 dpi), printer (300 dpi) and default.
pdfunite in-1.pdf in-2.pdf in-n.pdf out.pdf
pdftoppm file.pdf newfilename -png
pdftoppm file.pdf newfilename -png -f 2 -scale-to-x 1920 -scale-to-y -1 start from page 2 and scale FHD
Check the device name with lsblk and then use pmount device [ label ] and pumount to mount/unmount it. If label is given, the mount point will be /media/label,
otherwise it will be /media/device.
- Generate a keypair
gpg --full-gen-key. Warning: The passphrase is usually the weakest link in protecting your private key - List keys in your keyring
gpg --list-keys. Your keyring is in~/.gnupgmost likely - Export your public key
gpg --export --armor --output public.key user-id - Backup your private key
gpg --export-secret-keys --armor --output privkey.asc user-id. Place the key in a secure inaccessible place. - Import the backup of your private key
gpg --import privkey.asc
gpg --recipient user-id --armor --encrypt docin my casegpg -r hola@beachlab.org -a -e fileit will output an asciifile.asc- To decrypt
gpg -o file -d file.pgp
Install the jamessan/vim-gnupg plugin. Adjust the default recipient in .vimrc options. Here's mine
" GPG options
let g:GPGPreferArmor=0
" set the default option
let g:GPGDefaultRecipients=["me@beachlab.org"]
If the file extension is not md add at the bottom of the file /* vim: set filetype=markdown : */
Symmetric encryption does not require the generation of a key pair and can be used to simply encrypt data with a passphrase.
- To encrypt a file*
gpg -c filenameoutputsfilename.gpg. To decrypt a filegpg filename.gpg. - To encrypt directories
gpgtar -c -o file.gpg dirname. To decrypt a directorygpgtar -d file.gpg
You will then be prompted for a passphrase.
When you need to hide a secret you can encrypt the file. But an adversary will know that something is hidden, and they can attempt to break the code by putting some brute force. But if you embed this encrypted secret into an apparently normal file. The third person would not even be aware of the fact that a seemingly harmless looking image or audio file carries a secret message or a file embedded in it. This type of encryption where you hide one file securely into another is called Steganography. And I use it a lot.
Install steghide command line utility. To embed a secret into an image run:
steghide embed -ef secret.ggp -cf image.jpg
You will need another passphrase to embed the secret into the image. To extract the secret from the image
steghide extract -sf image.jpg
I keep my custom commands in a file called .custom_functions.sh. This file is sourced by .bashrc where I added this line at the bottom source .custom_functions.sh. Inside the file .custom_functions.sh I create my custom functions:
my_function () {
place your code here
}
Move it to ~/.local/share/fonts. More info here
For displaying siji fonts in Polybar xfd -fa 'Wuncon Siji'
Note the glyph code and display display it in a terminal replacing 0x00 printf "\ue0d4"
Copy that character and paste in want it in polybar config file
And it will show properly in polybar
Clone the repo with the font. Install gbdfed, add/edit a glyph, save it and run install.sh
Note: Sometimes after rebooting siji fonts are not displayed in polybar until I reinstall the font again and reload polybar. #TOFIX
I use TigerVNC for it's easy use.
Place a password/passphrase in ~/.vnc/passwd
To start x0vncserver -display :0 -passwordfile .vnc/passwd
To stop just close the terminal process.
xrandr
Useful for showing real dimensions at 100% xrandr --fbmm 310x175
This should work xrandr --output HDMI1 --set underscan on --set "underscan vborder" 25 --set "underscan hborder" 40 but it is not working in my case
In order to create a dummy serial port for developing purposes install tty0tty-git AUR package and load the module:
sudo depmod
sudo modprobe tty0ttyYou will see a number of serial ports /dev/tntx, make sure you give them permissions
sudo chmod 666 /dev/tnt*For testing printers and other devices, just send to /dev/null
tput colstells you the number of columns.tput linestells you the number of rows.
Edit ~/.config/xfce4/helpers.rc and add/edit TerminalEmulator=urxvt and then add a custom action in Thunar:
exo-open --working-directory %f --launch TerminalEmulator
Install cronie package and systemctl start cronie && systemctl enable cronie. List cron jobs with crontab -l. Add jobs with crontab -e. This is my crontab with a snippet as a cheat sheet:
#* * * * * command to be executed
#- - - - -
#| | | | |
#| | | | +----- day of week (0 - 6) (Sunday=0)
#| | | +------- month (1 - 12)
#| | +--------- day of month (1 - 31)
#| +----------- hour (0 - 23)
#+------------- min (0 - 59)
# Clear cache every Monday at 10pm
0 22 * * 1 yay -Scc --noconfirmYou can also use keywords instead @yearly @monthly @weekly @daily @hourly @reboot. Cron jobs are great to do some background tasks while your computer is on.
There are some other jobs you want to execute at specific intervals, and when you miss a scheduled task, as soon as the computer is up. Cronie includes anacron which processes jobs asynchronously, even if the computer was down at the time of the job. My /etc/anacrontab
# /etc/anacrontab: configuration file for anacron
# See anacron(8) and anacrontab(5) for details.
SHELL=/bin/sh
PATH=/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=root
# the maximal random delay added to the base delay of the jobs
RANDOM_DELAY=45
# the jobs will be started during the following hours only
START_HOURS_RANGE=3-22
#period in days delay in minutes job-identifier command
1 5 cron.daily nice run-parts /etc/cron.daily
7 25 cron.weekly nice run-parts /etc/cron.weekly
@monthly 45 cron.monthly nice run-parts /etc/cron.monthly
# Clear cache every Monday at 10pm
7 15 clear-cache-weekly yay -Scc --noconfirmYou can check the validity of your anacrontab file with anacron -T
pandoc --extract-media=. -s file.docx --wrap=none --reference-links -t markdown_strict -o file.md
for a batch of files
for i in *.docx ; do echo '$i' && pandoc --extract-media=. -s $i --wrap=none --reference-links -t markdown_strict -o $(basename $i .docx).md ; done
To resize windows I use the package wmctrl. To list current opened windows wmctrl -l
0x0140000b 3 hal unix@hal:~/Repositories/Fab/interspecies2021
0x0120000b 3 hal daily.md + (~/Repositories/Beach Lab/myComputing/doc) - VIM
0x02200003 1 hal Resizing a window to a set size in Linux - Stack Overflow — Mozilla Firefox
0x02c0001e 2 hal Zoom - Licensed Account
0x02c00028 2 hal Zoom Meeting
0x02c0002b 2 hal Zoom
0x02c0003a 2 hal SettingsYou can resize with wmctrl -r 0x02c00028 -e 0,0,0,1280,720 or interactively in a script
#!/usr/bin/sh
wmctrl -l
echo ""
read -p "window id -> " wid
read -p "width -> " ww
read -p "height -> " wh
wmctrl -i -r $wid -e 0,0,0,$ww,$wh
echo "Done!"