Upgrade git from upstream

(Debian)

As of 2015, most Debian variants provide git 1.9.4. To upgrade to the 2.x line, use the Git core PPA as follows:

sudo add-apt-repository ppa:git-core/ppa
sudo apt-get update
sudo apt-get install git

$ git --version
git version 2.5.0

Install emacs from source

mkdir /tmp/emacs

cd /tmp/emacs

wget https://ftp.gnu.org/pub/gnu/emacs/emacs-24.4.tar.xz 

tar xvf emacs-24.4.tar.xz 

cd emacs-24.4 

./configure --prefix=/usr        \
            --without-gnutls     \
            --localstatedir=/var &&
make

if make succeeds, you can test the result by running src/emacs -Q 

sudo make install && sudo chown -v -R root:root /usr/share/emacs/24.4

For a desktop launcher:

vim cat <<EOF > /usr/share/applications/emacs.desktop 

[Desktop Entry]
Version=1.0
Name=Emacs-24
Exec=/usr/local/bin/emacs
Terminal=false
Icon=emacs
Type=Application
Categories=IDE
[NewWindow Shortcut Group]
Name=New Window

EOF

Desktop .bashrc

case $- in
    *i*) ;;
      *) return;;
esac

shopt -s histappend
HISTSIZE=1000
HISTFILESIZE=2000
HISTCONTROL=ignoreboth

shopt -s checkwinsize

if [ -z "${debian_chroot:-}" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

case "$TERM" in
    xterm|xterm-color|*-256color) color_prompt=yes;;
esac

force_color_prompt=yes

case "$TERM" in
xterm*|rxvt*)
    LIGHT_GRAY="\[\033[0;37m\]"; BLUE="\[\033[1;36m\]"; RED="\[\033[0;31m\]"; LIGHT_RED="\[\033[1;31m\]";
    GREEN="\[\033[0;32m\]"; WHITE="\[\033[1;37m\]"; LIGHT_GRAY="\[\033[0;37m\]"; YELLOW="\[\033[1;33m\]";
    function parse_git_branch {
        git branch --no-color 2> /dev/null | sed -e '/^[^*]/d' -e 's/* \(.*\)/ \(\1\)/';
    }
    function parse_git_status {
        git status 2> /dev/null | sed -e '/(working directory clean)$/!d' | wc -l;
    }
    function check_git_changes {
        # tput setaf 1 = RED, tput setaf 2 = GREEN
        [ `parse_git_status` -ne 1 ] && tput setaf 1 || tput setaf 2
    }
    export PS1="($(whoami)@$(hostname)) \[$(tput bold)\]\[$(tput setaf 2)\]$(date +%F\|%R) $YELLOW\w\[\$(check_git_changes)\]\$(parse_git_branch)$LIGHT_GRAY\n $ "
    export PS4='+(${BASH_SOURCE}:${LINENO})'
    ;;
*)
    ;;
esac

set -o emacs
umask 002
export HISTTIMEFORMAT="%F %T "
shopt -s histappend

export TZ='/usr/share/zoneinfo/US/Eastern'
export PROMPT_COMMAND="${PROMPT_COMMAND:+$PROMPT_COMMAND$'\n'}history -a; history -c; history -r"

alias l='ls -lF'
alias ll='ls -alF'

if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi

export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/jre

Export Gimp layers as separate files

Install plugin at https://github.com/khalim19/gimp-plugin-export-layers

Extract the export_layers.py file and the export_layers directory to [home directory]/.gimp-2.8/plug-ins.

If necessary, make the export_layers.py file executable, e.g. from the terminal:

chmod +x "export_layers.py"

Collate PDF documents

pdftk $(ls file*.pdf|sort) cat output combined.pdf

Tech links

• Vert.x: Reactive server for the JVM
• Wildfly, Apiman, Keycloak

Network traffic monitoring with tcpdump

tcpdump is a command-line network traffic analyzer. It allows capture of network packets from a host and subsequent filtering and display.

Sample applications

Show traffic into port 2003 from a given host

sudo tcpdump -A -nn 'port 2003 and src host 10.60.35.49'

Must run as root (sudo)
-A print ASCII payload
-nn numeric IP and ports

Snippets

# Sudo a long command line
sudo bash -c "
# Get 16th field
cut -f16 -d\| /data/sample.csv | 
# Render unicode as ASCII
iconv -f utf8 -t ascii//TRANSLIT | 
# Drop empty lines
sed '/^$/d' | 
# Filter for lines longer than 30 characters
awk 'length(\$0) > 30' > /data/sample.out"

NUMA, affinity and OS tuning

NUMA tuning and affinity (RHEL)
NUMA and optimization (Elasticsearch, Riak)

IRC cheat sheet

Register IRC nick

/msg NickServ REGISTER password youremail@example.com

Identify to primary IRC account:

/msg NickServ IDENTIFY account password

Get nick info

/msg NickServ INFO account

Reset password

/msg NickServ SET PASSWORD mynewpassword

Reset command hash

To flush the hash table used by the shell to remember the full path names of executable files:

hash -r

git recipes

Git: prune local branches without remotes

git branch -vv | grep ': gone]' | awk '{print $1}' | xargs git branch -D 

Cache git credentials (Linux)

While it is possible to store git credentials locally via .netrc, that requires storing them in plain text. Even with 400 permissions, it is an unnecessary risk. I have read references about using GPG for encryption within this file, which increases security, but introduces a new dependency. When changing hosts frequently, local dependencies become highly impractical. Instead, to cache the credentials in memory with an expiration timeout, one hour, for example:

git config --global credential.helper 'cache --timeout=3600'