Miscellaneous Cheat Sheet

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A quick reference to all things miscellaneous and those things that have no home yet.

Created on: 2020-02-09

Tag: cheat_sheet

HTML: jump to top of page link

to create a jump to top of page link:

<a href="#">Go to top</a>

<a href="#top">Go to top</a>

source: https://stackoverflow.com/a/11751756

CSS: Comments

to add comments in CSS:

/* This is a single-line comment */

/* This is
a multi-line
comment */

source: https://www.w3schools.com/Css/css_comments.asp

Linux

best place to store SSL certificate and key

store SSL certificate inside:

/etc/ssl/certs

with 777 file permission.

store SSL key inside:

/etc/ssl/private

with 700 file permission.

source: https://stackoverflow.com/a/4267602

Download all mvk files in a HTML page

Sometime we would need to download all the file of same type from an HTML page. We would do this with:

wget --no-directories -r -l 1 --accept='*.mkv*' $LINK

source: https://serverfault.com/a/359926

Resume download with wget

To resume download with wget:

wget -c $LINK

source: https://unix.stackexchange.com/a/165881

Download only new files with wget

to download only new files with wget:

wget -N $LINK

source: https://superuser.com/a/283484

Download all new files from a HTML page with resume

If we combine all the above cheats we can download all new files of a type from a HTML page with resume:

wget --no-directories -r -l 1 -N -c --accept='*.ext*' $LINK

Hide a particular user from login screen

To hide a particular user from the login screen, first create a file with a text editor:

sudo vim /var/lib/AccountsService/users/$USER_NAME

put the following:

[User]
SystemAccount=true

If the file already exist the change the value of SystemAccount to true, then save and exit the file.

source: https://askubuntu.com/a/575390

Disable user list on login screen

To disable user list on login screen, first create a directory, lightdm.conf.d inside /etc/lightdm/:

sudo mkdir -p /etc/lightdm/lightdm.conf.d

Now create a file with a text editor named 10-ubuntu.conf:

sudo vim /etc/lightdm/lightdm.conf.d/10-ubuntu.conf

Next put the following in that file:

[SeatDefaults]
user-session=ubuntu
greeter-show-manual-login=true
greeter-hide-users=true
allow-guest=false

Change the user-session to reflect your user session, for example, in Xubuntu the value would be xubuntu. Then save and exit the file. The effect will be visible after a reboot.

source: https://askubuntu.com/a/731455

Specifically for Ubuntu the following can done as well:

sudo -i

xhost +SI:localuser:gdm
su gdm -l -s /bin/bash
gsettings set org.gnome.login-screen disable-user-list true

source: http://ubuntuhandbook.org/index.php/2018/04/hide-user-list-ubuntu-18-04-login-screen/

Bash autocomplete files location

System-wide bash autocomplete files location:

/etc/bash_completion.d/

source: https://askubuntu.com/a/68203

Open apt manager from URL

to open apt manager from URL:

apt:$PACKAGE_NAME

In HTML:

<a href="apt:package">click</a> # single package
<a href="apt:package1,package2,package3">click</a> # multipule packages

Needs to be Ubuntu 7.10 or later with apturl package installed and in a compatible browser.

source: https://help.ubuntu.com/community/AptURL and https://wiki.ubuntu.com/AptUrl

Do nothing when lid is closed

to take no action when lid is closed, edit the /etc/systemd/logind.conf file to add:

HandleLidSwitch=ignore

and the edit /etc/UPower/UPower.conf file to add:

IgnoreLid=true

sometime WiFi is still disconnects after doing this step then we may also need to add the following in the /etc/systemd/logind.conf:

HandleLidSwitchDocked=ignore

In Ubuntu 20.04 I am noticing a new option HandleLidSwitchExternalPower in the /etc/systemd/logind.conf file. We can use it as well:

HandleLidSwitchExternalPower=ignore

source: https://askubuntu.com/a/830562

see desktop environment in use

to see desktop environment in use:

echo $DESKTOP_SESSION

source: https://askubuntu.com/a/125072

remove all KDE desktop element

to remove all KDE desktop element:

sudo apt-get purge '^kde' '^kubuntu' '^plasma'

source: https://askubuntu.com/a/829127

ubuntu server enable root user

to enable root user in Ubuntu server, first set the password for root user:

sudo passwd root

then unlock the user:

sudo passwd -u root

we can disable root user by locking:

sudo passwd -l root

source: https://askubuntu.com/a/44419

mount directory over ssh

to mount directory over ssh, we can use sshfs. First we will install it:

sudo apt-get install sshfs

Then enable the fuse kernel module:

sudo modprobe fuse

Now create a directory and mount remote directory to that directory:

mkdir $DIR

sshfs $USER_NAME@$SERVER_IP:/$PATH $DIR

To unmount simply do:

umount $DIR

source: https://askubuntu.com/a/412478

apt upgrade single package

to upgrade single package with apt:

sudo apt install --only-upgrade $PACKAGE_NAME

source: https://askubuntu.com/a/44124

QR Code

Bangladesh Railway Online Ticket

If we scan it, we see:

TRAIN: NELSAGORE_EXPRESS (765.)     // train name and number
STATION: DHAKA to ABDULPUR          // source station to distination station
DATE: 01-JAN-1001 08:00             // date and time of train diperture from source station
CLASS: S_CHAIR                      // seat class
COACH_NO: CHA                       // coach number
SEAT_RANGE: 1,2                     // seat number
E-PIN: 6NZ95                        // e-pin number
FULL NAME: Jane Doe                 // name of passenger
MOBILE_NO: 01704522104              // phone number of passenger
PNR_NO: 1704522104                  // not sure what is it
ID: 1382533015                      // ID of user
GATEWAY: EBL_BANK                   // bank with what the payment was made

Dhaka University Masters Admit

If we scan it, we see:

DU-ADMT<<<1001822312<<REF<<19966095654<<Regular<<62867<<<
               ^                ^          ^       ^
               |                |          |       |
         registration       referance    type     roll
         number like:         number      of     number
         1001-822-312                   student
          ^
          |
    registration
       year!?

Nextcloud App Password

If we scan it, we see:

nc://login/user:$USER-NAME&password:$PASSWORD&server:$PROTOCOL://URL:$PORT-IF-ANY

VeraCrypt

mount volume from command line

to mount a VeraCrypt volume from command line:

veracrypt -t --mount /dev/sdb1 --non-interactive --stdin

This will be stuck on a blank line. Typing the volume password would mount the volume. The -t flag is for text user interface, the --mount flag mounts volume interactively which takes a device path as argument, --non-interactive flag disabals user interaction and finally the --stdin flag reads password from standard input.

source: https://www.veracrypt.fr/en/Command%20Line%20Usage.html. Thought not all options are document there and needed to be look at the veracrypt -t --help.

unmount volume from command line

to unmount a VeraCrypt volume from command line:

veracrypt -d

The -d flag dismounts volume.

source: https://www.veracrypt.fr/en/Command%20Line%20Usage.html

list volume from command line

to list VeraCrypt volume(s) from command line:

veracrypt -t -l

The -l flag displays a list of mounted volumes.

source: veracrypt -t --help options.

console shows gibrish error

every time a command is run with -t flag a gibrish error showed in the terminal. Bit of searching the web showed it happens because of X11 over ssh and can be fixed with:

export DISPLAY=:0.0

source: https://github.com/veracrypt/VeraCrypt/issues/531#issuecomment-548879342

read only after mounting on Windows

VeraCrypt sometimes becomes read only after mounting on Windows because of Metadata kept in Windows cache.

sudo ntfsfix -b -d "/dev/mapper/veracrypt$N"

source: https://superuser.com/questions/1115813/cannot-mount-veracrypt-partition-on-linux-mint-metadata-kept-in-windows-cache#comment1976408_1125460 and https://www.reddit.com/r/VeraCrypt/comments/a0uzur/mounting_a_veracrypt_volume_as_writable

don't prompt for format in windows

need to test this: https://superuser.com/a/324590

Facebook: See most recent post

The new Facebook UI (as of Mar 16, 2020 it is in early adopter phrase) don't have a option to see most recent post. I noticed a URL change in the old UI which works in the new UI.:

https://www.facebook.com/?sk=h_chr

Tomcat: Web Server Location in Linux

The location of the Tomcat server in Linux:

/var/lib/tomcat7/webapps/

source: https://stackoverflow.com/a/39671086

OpenVPN: Restrict one cert per device

To restrict one cert per device in OpenVPN comment out or DO NOT USE the --duplicate-cn option.

source: https://forums.openvpn.net/viewtopic.php?t=18164#p49452

KeePass: Password generator character set

KeePass Password generator as the following character set available:

Upper-case: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Lower-case: abcdefghijklmnopqrstuvwxyz
Digits: 0123456789
Minus: -
Underline: _
Space:
Special: !"#$%'*+,./:;=?@\^`|~
Brackets: []{}()<>
Latin-1 Supplement: ¡¢£¤¥¦§¨©ª«¬­®¯°±²³´µ¶·¸¹º»¼½¾¿ÀÁÂÃÄÅÆÇÈÉÊËÌÍÎÏÐÑÒÓÔÕÖ×ØÙÚÛÜÝÞßàáâãäåæçèéêëìíîïðñòóôõö÷øùúûüþÿ

First message of Telegram

channel: Channel created

group: $CREATORS_DISPLAY_NAME created the group «GROUP_NAME»

Source

View document source. Generated on: 2020-06-02 05:59 UTC.