Apologia, decisions, & consequences
A few quirks with Debain 12 include that path not being set in similar fashion to Fedora, Ubuntu, and other distributions. One must regularly set
export PATH=$PATH:/usr/sbin
In Gnome, applications will open on the server instead of the client when using X11 forwarding. This will occur even though xcalc opens on the client normally. The way to avoid this is to add the following to .bashrc
unset XDG_RUNTIME_DIR unset GDK_BACKEND
The general rule is compress, then encrypt.1, 2
Use printenv to see what environment variables are set.
#!/usr/bin/env bash
printenv
set -x
The .bashrc file I use on CentOS6
# .bashrc
# User specific aliases and functions
alias rm='rm -i'
alias cp='cp -i'
alias mv='mv -i'
# Source global definitions
if [ -f /etc/bashrc ]; then
. /etc/bashrc
fi
# system variables
export VISUAL=nano # sets nano as the crontab editor
export GZIP=-9 # maximum compression
export XZ_OPT=-9 # maximum compressions
# ls modifications
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'
# calculator
calc() { echo "$*" | bc -l; }
# Generate a UUID
uuid() { UUID=$(cat /proc/sys/kernel/random/uuid) && echo $UUID; }
# CHANGE SHELL/WINDOW TITLE
# Works on Opensuse 15.3
# PS1=$PS1"\[\e]0;test1\a\]"
shellrename() { read -p "Enter new shell name: " name && PS1=$PS1"\[\e]0;${name}\a\]"; }
# For older versions of gnome-terminal
# shellrename() { read -p "Enter new shell name: " name && PROMPT_COMMAND='echo -ne "\033]0;${name}\007"'; }
# Zen Burn
# Another old way that works great in gnome-terminal while causing problems
# in some configurations involving SSH:
echo -ne '\e]12;#BFBFBF\a'
echo -ne '\e]10;#DCDCCC\a'
echo -ne '\e]11;#3F3F3F\a'
echo -ne '\e]4;0;#3F3F3F\a'
echo -ne '\e]4;1;#705050\a'
echo -ne '\e]4;2;#60B48A\a'
echo -ne '\e]4;3;#DFAF8F\a'
echo -ne '\e]4;4;#506070\a'
echo -ne '\e]4;5;#DC8CC3\a'
echo -ne '\e]4;6;#8CD0D3\a'
echo -ne '\e]4;7;#DCDCCC\a'
echo -ne '\e]4;8;#709080\a'
echo -ne '\e]4;9;#DCA3A3\a'
echo -ne '\e]4;10;#C3BF9F\a'
echo -ne '\e]4;11;#F0DFAF\a'
echo -ne '\e]4;12;#94BFF3\a'
echo -ne '\e]4;13;#EC93D3\a'
The best alias for ls is
ls –halF
It is easy to remember, and produces easy to read output with human readable file sizes and / marks present by the directory names..
A really good version of the ll alias is:
ls –lahF, although on some versions ls –lahp looks better than F.
The following script scans PDFs via an auto-document feeder in Hp-Lip and then collates the pages to the correct order when there are reverse sides. No scans will be saved if no data is transmitted for the second set of scans. The second set of scans is the reverse of the pages.
#!/usr/bin/env bash
YMD=$(date +"%Y-%m-%d")
Y=$(date +"%Y")
WORKDIR=/home/username/Temp/
OUTPATH=/home/username/Scans/${Y}/
# Create a folder, ~/Temp and create a folder, ~/Scans
mkdir -p "/home/username/Scans/${Y}"
hp-scan --adf --mode=color &&
PART=hpscan
LATESTSCAN=`ls -t ${PART}*pdf | sed "1q"`
echo "${LATESTSCAN} ready for ${FILEOUTPUT}"
# Why you shouldn't parse the output of ls
# http://mywiki.wooledge.org/ParsingLs
# This does not use the FILEOUTPUT variable itself because the cp command
# seems to have trouble copying the file correctly, even with switches.
# Thanks Elektropepi at https://github.com/qpdf/qpdf/issues/259
function pdfscanmerge() {
if [ $# -ne 3 ]; then
echo "Usage: pdfscanmerge
Here is a script that checks to ensure the database is running and restarts the service if it is not running. This was used on a very low memory server to ensure a database remained operational, despite it sometimes crashing due to out of memory errors.
#!/bin/bash
timestamp="$(date)"
systemctl stop httpd && echo "${timestamp}" Stopping Apache... >> /home/centos/administration/apache.log
systemctl is-active mariadb && echo "${timestamp}" MariaDB is active so not starting >> /home/centos/administration/mariadb_active.log || echo "${timestamp}" MariaDB is not Active >> /home/centos/administration/mariadb_inactive.log
systemctl is-active mariadb && echo "${timestamp}" No need to restart MariaDB || systemctl start mariadb
systemctl start httpd && echo "${timestamp}" restarting apache...>> /home/centos/administration/apache.log
This is the code for a function in Bash script.
#!/bin/bash # Define a functiongreet() { echo "Hello, $1" } # Call the function with "World" as the argument greet "World"
To loop through the subdirectories in a folder, when those subdirectories may contain spaces in the file names, use the following procedure.
OLD_IFS=$IFS && IFS=$'\n' for directory in $HOME/somefolder/*/; do echo “some code here” done IFS=$OLD_IFS
This document contains some notes on .bashrc for use with Linux systems.
alias ll=’ls -alF’
alias la=’ls -A’
alias l=’ls –CF’
if [ -f ~/.bash_aliases ]; then
. ~/.bash_aliases
fi
The preceding two blocks come standard on Ubuntu as of version 2022.04. One tweak for WSL2 on Windows might be the addition of this line.
sudo bash “/etc/rc.local”
and in the rc.local follow, add the following.
#!/bin/bash
rm -f /etc/resolv.conf
echo “nameserver 1.1.1.1″ >> /etc/resolv.conf
echo “nameserver 8.8.8.8″ >> /etc/resolv.conf
This is because WSL2 may place non-routable IP addresses using 172… in resolv.conf. As of this writing, following steps recommended to disable the generation of the file fails to resolve the issue where the file is newly generated with every new terminal launched in Windows terminal. Having this run with each new Bash login ensures success with network communications. The location /etc/rc.local may seem like an odd location for this.
The crontab to ensure to check each minute to ensure a virtual machine is running in VirtualBox is as follows.
*/1 * * * * VBoxManage startvm “VMNAME” –type headless
*/1 * * * * VBoxManage startvm “VMNAME2″ –type headless
If the virtual machine is already running, then it will not start a new copy of it. This is better than attempting to run the script via a system wide script after a reboot. Running it this way allows a simple crontab for the user for whom the machine needs to run under. To run a script every five minutes, add the crontab as follows:
*/5 * * * * /home/USERNAME/nextcloudcron
In this example, the nextcloudcron script will run every five minutes. This particular script is one for use contacting my Nextcloud instance for webcron. It does not contain a .sh on the filename, because some implementations may disallow crontab scripts with file extensions.
The following checks inside a subdirectory and pulls in the files therein as bash sources. This is useful for breaking aliases, variables, and other items into different files.
if [ -d ~/.bashrc.d ]; then
for rc in ~/.bashrc.d/*; do
if [ -f "$rc" ]; then
. “$rc”
fi
done
fi
The following uses nano as the crontab editor.
export VISUAL=nano
On Oracle Linux 9 on AWS, it is necessary to install Cronie to enable cron jobs. To ensure this starts after reboots, add the following to /etc/rc.local.
bash /sbin/crond
To create a date line for a log file, use the following:
echo $(date) >> /home/USER/FILENAME
The Shebang for the top of bash files is
#!/usr/bin/env bash
To auto-update via DNF and leave a log of what was accomplished, use the following script. The script will write a list of the updates to the systemupdates.log file, and then update the system with details of that process written to the dnfupdates.log file.
#!/usr/bin/env bash
echo $(date) >> /home/USER/systemupdates.log
sudo dnf check-update >> /home/USER/systemupdates.log
echo $(date) >> /home/USER/dnfupdates.log
sudo dnf update -y >> /home/USER/dnfupdates.log 2>&1
7 July 2023:
Ubuntu 22.04′s update notifier seems to not include the option to configure any settings, at least after certain conditions exist on a particular system. To stop the notifier from appearing. To stop the notifier from appearing use
sudo apt-get remove update-notifier
7 July 2023:
There are non-snap builds of ungoogled-chromium for Ubuntu
6 July 2023 and prior:
To disable automatic updates on Ubuntu:
sudo dpkg-reconfigure unattended-upgradessudo apt remove packagekit
In .bashrc create the following alias:
alias nano="nano -c --guidestripe 80"
This will open always Nano with line and column numbering along with a long line marker at the specified column. The long line marker feature works for Nano version higher than 4, which doesn’t include the version in the CentOS 7 repositories.
In .bashrc add the following line:
export DISPLAY=\ "`grep nameserver /etc/resolv.conf | sed 's/nameserver //'`:0"
This adds the IP address of the instance to the display variable for use with Windows Subsystem for Linux and VcXsrv.
In .nanorc add the following items. The first two lines are commented because the command line switch used in the alias for the line numbers creates no artifacts when using copy-paste.
#set linenumbers #set constantshow # https://www.nano-editor.org/dist/latest/nanorc.5.html set guidestripe 80 include /usr/share/nano/autoconf.nanorc include /usr/share/nano/patch.nanorc include /usr/share/nano/nanorc.nanorc include /usr/share/nano/groff.nanorc include /usr/share/nano/awk.nanorc include /usr/share/nano/man.nanorc include /usr/share/nano/java.nanorc include /usr/share/nano/sh.nanorc include /usr/share/nano/po.nanorc include /usr/share/nano/texinfo.nanorc include /usr/share/nano/python.nanorc include /usr/share/nano/perl.nanorc include /usr/share/nano/pov.nanorc include /usr/share/nano/ocaml.nanorc include /usr/share/nano/tcl.nanorc include /usr/share/nano/debian.nanorc include /usr/share/nano/lua.nanorc include /usr/share/nano/xml.nanorc include /usr/share/nano/gentoo.nanorc include /usr/share/nano/objc.nanorc include /usr/share/nano/tex.nanorc include /usr/share/nano/guile.nanorc include /usr/share/nano/php.nanorc include /usr/share/nano/c.nanorc include /usr/share/nano/nftables.nanorc include /usr/share/nano/spec.nanorc include /usr/share/nano/elisp.nanorc include /usr/share/nano/ruby.nanorc include /usr/share/nano/go.nanorc include /usr/share/nano/nanohelp.nanorc include /usr/share/nano/default.nanorc include /usr/share/nano/json.nanorc include /usr/share/nano/css.nanorc include /usr/share/nano/mgp.nanorc include /usr/share/nano/asm.nanorc include /usr/share/nano/mutt.nanorc include /usr/share/nano/javascript.nanorc include /usr/share/nano/postgresql.nanorc include /usr/share/nano/rust.nanorc include /usr/share/nano/fortran.nanorc include /usr/share/nano/cmake.nanorc include /usr/share/nano/makefile.nanorc include /usr/share/nano/html.nanorc include /usr/share/nano/changelog.nanorc
Using Tar and Gzip:
tar -zcvf output_file_name[.tar.gz or .tgz] directory_to_compress
tar -Jcvf output_file_name[.tar.xz] directory_to_compress
reads compression level for XZ from environmental variable, but note that xz utils is not installed by default on ubuntu 10.04tar -xvf works to extract .tar.gz file created like in the above
The Tar and Gzip commands use compression settings specified in .bashrc
export GZIP=-9 export XZ_OPT=-9
Add the following to .bashrc for a console calculator:
calc() { echo "$*" | bc -l; }
For the ll alias, use the following in .bashrc
alias ll='ls -alF'
To change the terminal name use the following in .bashrc. The command differs depending upon which version of Gnome one uses.
# For older versions of gnome-terminal
#shellrename() { read -p "Enter new shell name: " name && PROMPT_COMMAND='echo -ne "\033]0;${name}\007"'; }
# Works on OpenSUSE 15.3
#PS1=$PS1"\[\e]0;test1\a\]"
shellrename() { read -p "Enter new shell name: " name && PS1=$PS1"\[\e]0;${name}\a\]"; }
To obtain a uuid, add the following to .bashrc:
uuid() { UUID=$(cat /proc/sys/kernel/random/uuid) && echo $UUID;
Zen Burn color scheme for the terminal, but sometimes causes problems with work via SSH.
# Zen Burn # Another old way that works great in gnome-terminal while causing problems # in some configurations involving SSH: echo -ne '\e]12;#BFBFBF\a' echo -ne '\e]10;#DCDCCC\a' echo -ne '\e]11;#3F3F3F\a' echo -ne '\e]4;0;#3F3F3F\a' echo -ne '\e]4;1;#705050\a' echo -ne '\e]4;2;#60B48A\a' echo -ne '\e]4;3;#DFAF8F\a' echo -ne '\e]4;4;#506070\a' echo -ne '\e]4;5;#DC8CC3\a' echo -ne '\e]4;6;#8CD0D3\a' echo -ne '\e]4;7;#DCDCCC\a' echo -ne '\e]4;8;#709080\a' echo -ne '\e]4;9;#DCA3A3\a' echo -ne '\e]4;10;#C3BF9F\a' echo -ne '\e]4;11;#F0DFAF\a' echo -ne '\e]4;12;#94BFF3\a' echo -ne '\e]4;13;#EC93D3\a'
Circa 2015: Adding Windows to CentOS 7 and Grub 2 after installing CentOS and no automatic configuration of Windows boot options. The file to manually edit is /etc/grub.d/40_custom.
menuentry "Windows 10 Professional" { set root=(hd0,1) chainloader +1 }
After editing, update Grub and reboot using the following command.
grub2-mkconfig –output=/boot/grub2/grub.cfg
The following shows one of the custom file contents circa 2018 or 2019 after some changes to installers and autodetection.
#!/bin/shexec tail -n +3 $0# This file provides an easy way to add custom menu entries. Simply type the menu entries you want to add after this comment.# Be careful not to change the 'exec tail' line above.menuentry "Windows (system) (on /dev/sda1)" --class windows --class os { insmod part_msdos insmod ntfs insmod ntldr set root='(hd0,msdos1)' ntldr ($root)/bootmgr}
To launch
java -Xms2048M -Xmx2048M --add-modules=jdk.incubator.vector -XX:+UseG1GC -XX:+ParallelRefProcEnabled -XX:MaxGCPauseMillis=200 -XX:+UnlockExperimentalVMOptions -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:G1HeapWastePercent=5 -XX:G1MixedGCCountTarget=4 -XX:InitiatingHeapOccupancyPercent=15 -XX:G1MixedGCLiveThresholdPercent=90 -XX:G1RSetUpdatingPauseTimePercent=5 -XX:SurvivorRatio=32 -XX:+PerfDisableSharedMem -XX:MaxTenuringThreshold=1 -Dusing.aikars.flags=https://mcflags.emc.gs -Daikars.new.flags=true -XX:G1NewSizePercent=30 -XX:G1MaxNewSizePercent=40 -XX:G1HeapRegionSize=8M -XX:G1ReservePercent=20 -jar server-1.21.1.jar nogui