Tag Archives: python

Too Good To, UNIX & Linux

Too good to #0008

rinetd-style circuit level gateway in systemd

This accepts port 465/tcp and forwards all connections to a service running somewhere else on 1194/tcp.

The socket unit accepts the connection on port 465:

# /etc/systemd/system/tcp465-to-tcp1194.socket
[Unit]
Description="openvpn 465/tcp to 1194/tcp (socket)"

[Socket]
ListenStream=465

[Install]
WantedBy=sockets.target

systemd-socket-proxyd connects to the backend:

# /etc/systemd/system/tcp465-to-tcp1194.service
[Unit]
Description="openvpn 465/tcp to 1194/tcp (service)"

[Service]
ExecStart=/lib/systemd/systemd-socket-proxyd 10.12.13.14:1194
User=proxy

(Anyone old enough to remember that this was called a plug-gateway in the TIS Firewall Toolkit?)

Python pip/virtualenv/pipenv micro-HOWTO

Clone project with wacky dependencies:

git clone https://github.com/example/project.git

Install dependencies (from requirements.txt):

pipenv install (-r requirements.txt)

Run:

pipenv run ./script

Template for git commit message

Create the template, I prefer it outside the repository:

(blank line)
(blank line)
foo#1234 is the neverending story I'm constantly working on

Configure the path, relative to the repository root:

git config commit.template ../commit-template-for-foo.txt
Too Good To, UNIX & Linux

Too good to #0004

1 Comment

systemd, the good parts: monotonic timers

When systemd makes you suffer because “run job every 10 minutes” is infinitely harder to specify than in crontab, remember there are monotonic timers in systemd that aren’t derived from wallclock time, or “Calendar Events” as they call it.

Run timer once 60 seconds after system startup, then every 10 minutes after the job finished:

# /etc/systemd/system/demo.timer
[Unit]
Description=demo monotonic timer

[Timer]
OnStartupSec=60
OnUnitInactiveSec=600

[Install]
WantedBy=timers.target    # When in a system session
# WantedBy=default.target # When in a user session (~/.config/systemd, systemctl --user etc.)

Python: Use tabulate to format output in columns 

#!/usr/bin/env python3
from tabulate import tabulate

data = [
	[ 'foo', 'bar', 'baz' ],
	[ 'spam', 'eggs', 'bacon' ]
]

headers = ['Eine', '2', 'Whatever']

print(tabulate(data, headers=headers, tablefmt='simple'))

Output:

$ ./tab.py 
Eine    2     Whatever
------  ----  ----------
foo     bar   baz
spam    eggs  bacon

virsh/libvirt, automate key presses

(* Updated to sleep 5 seconds after each keypress.)

for key in R E I S U B; do virsh send-key "${domain}" KEY_LEFTALT KEY_SYSRQ KEY_${key}; sleep 5; done