• Shellsheet
  • Ubuntu (Debian?) specific
    • SSH Config
    • Application shortcuts
    • Remote File Transfer
    • Archive Files
    • PDF Files
    • Special keys with AltGr Int'l keyboard

To search back in shell command history use Ctrl+r (this is called "reverse-i-search"). Can use Ctrl+s to search forward, but possibly need to remap an overshadowing shortcut for this key combination ("stop terminal sequence"), adding stty stop ^J to .bashrc (see here).

!<command prefix> executes last command starting with prefix. history shows command history.

Safe fstab line: UUID=<device UUID> <mountpoint> none <options> 0 0 Mountpoint must exist. Can check UUID with lsblk

Worth to almost always use nofail to allow the system to boot even if the drive cannot be mounted. E.g. replace <options> with defaults,nofail.

For network-facing systems, worth to use safe options nosuid,nodev.

Mount ntfs filesystem:

UUID=F4E2C7FAE2C7BF5C /media/Windows ntfs defaults,nofail,nls=utf8,umask=000,dmask=027,fmask=137,uid=1000,gid=1000,windows_names 0 0

Can use lsblk -o NAME,MOUNTPOINT,SIZE,FSTYPE,UUID command to list drives and found out UUID of an unmounted drive.

To hide a user from login screen see here:

sudo vim /var/lib/AccountsService/users/[username]

Add / edit the following two lines:

[User]
SystemAccount=true

Running ssh in the background (e.g. port-forwarding).

Installing: sudo apt-get install openssh-server

~/.ssh/config file format:

Host <my_alias>
HostName <ip>
User <remote username>
To connect through proxy, do
ProxyCommand ssh yurif@csm nc %h %p
or
ProxyJump pi

To execute a remote command on connect (e.g., `cd` to some directory)
RequestTTY yes # or 'force'
RemoteCommand cd /home/katya/yuri; exec /bin/bash

To avoid / reduce connection drops (especially sftp in Nautilus), on the client side, add:
ServerAliveInterval 180
ServerAliveCountMax 2
To apply to all connections add this under Host *, like this:
Host *
    ServerAliveInterval 180
    ServerAliveCountMax 2

.ssh/config file permissions need to be 644.

ssh connection parameters can be configured in /etc/ssh/sshd_config (globally) and in the $HOME/.ssh/config (per host). In particular, look at {Server,Client}Alive intervals which control how a connection is maintained alive, see above.

Taken from here.

sudo vim /etc/hostname
sudo vim /etc/hosts
sudo reboot

The nmap utility scans for open ports, e.g. sudo nmap -p 22 192.168.1.0/24 scans for machines listening on port 22 (ssh).

.desktop files located at /usr/share/applications. Can link also to remote folders through sftp.

To create a desktop shortuct, need to create a .desktop file at ~/Desktop.

rsync --partial --progress myfile username@server:/path/to/destination

Transfer file. --partial flag allows to resume an interrupted transfer. --remove-source-files and --delete deletes source after transfer. After --remove-source-files directory tree is left.

scp

TODO: Description

Convert PDF into (true) black-and-white (good for sending as fax):

gs -sDEVICE=bmpgray -dNOPAUSE -dBATCH -r300x300 -sOutputFile=./Payement-confirmation.pdf ./Payement-confirmation.pdf

gs -o ./Payement-confirmation-bw.pdf -sDEVICE=pdfwrite -c "/osetrgbcolor {/setrgbcolor} bind def /setrgbcolor {pop [0 0 0] osetrgbcolor} def" -f ./Payement-confirmation-b\&w.pdf

Convert PDF to png:

convert -density 700 input.pdf -quality 90 output.png

curl -sSL
'http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xBBEBDCB318AD50EC6865090613B00F1FD2C19886'
| sudo apt-key add -

Documentation here.

Crons are stored at /var/spool/cron/crontabs.

To schedule a command to run once can use the at command (might need to apt-get install it). For example

echo 'mycommand' | at 16:00   # at now + 3 hours

or

at 16:00 -f some_script.sh

References 1, 2.

Problem: AltGr special keys not function Ubuntu 18.04. Solution: Keyboard shortcuts ==> Restore keyboard shortcuts (Super+Escape default).

prefix = right alt

Also see here

Example

conda-workon() {
        module load conda; conda activate "$1"
}

_conda-workon_completions()
{
        if [ "${#COMP_WORDS[@]}" != "2" ]; then
        return
        fi

        envs_options="`ls $HOME/.conda/envs`"
        COMPREPLY=($(compgen -W "${envs_options}" "${COMP_WORDS[1]}"))
}

complete -F '_conda-workon_completions' 'conda-workon'

To enable for all users, add the completion script into /etc/bash_completion.d/

See here

sudo apt install libopencv-dev 
sudo apt install libpcl-dev

sudo apt-get install mc

Can choose Lynx-like motion in Options (F9) -> Panel options,

More information about macros etc. here

And here

And another excellent cheatsheet here

A separate access permissions mechanism for file systems via access lists, complementary to permissions flags.

Docs here: https://linux.die.net/man/1/setfacl

chmod g+rwxs
setfacl -m d:g::rwx

gsettings set org.gnome.shell.extensions.ding show-trash true
gsettings set org.gnome.shell.extensions.dash-to-dock show-trash false