Category: linux

Since the Raspberry Pi Zero and Zero W are not available in bulk quantity, I looked around for alternatives.  The C.H.I.P. seems to be a great option, but the company has been unable to fulfill it’s orders and the $9 version has been discontinued 🙁   The Banana Pi is a knock-off of the rPi but the cost is 50% to 100% more than the rPi.  Similar for the NanoPi, about double the cost.  Finally I found the Orange Pi, it’s costs are similar (some as low as $7) yet there’s many variations of it.  Trying to make sense of the options, I put together a table that compares some aspects of the oPi:

oPi-models

It’s easy to add multiple IP addresses to an interface in Linux. For example, you want to have both the address 172.16.0.13 and 192.168.0.17 for your Ethernet device. But, can we create LOTS and LOTS of addresses?

For fun, I wrote a little script to create bunches of alias addresses. I tested on a RedHat Enterprise 6.8 64bit VM (running kernel 2.6.32-642.el6.x86_64), since there’s still lots of this older o/s out there. I tried 50,000 alias addresses, and ta da! it works fine:

# ip addr
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
link/ether 08:00:27:76:75:29 brd ff:ff:ff:ff:ff:ff
inet 172.16.47.139/16 brd 172.16.255.255 scope global eth0
inet 192.168.0.1/32 scope global eth0:3232235521
inet 192.168.0.2/32 scope global eth0:3232235522
inet 192.168.0.3/32 scope global eth0:3232235523
inet 192.168.0.4/32 scope global eth0:3232235524
. . .
inet 192.168.195.77/32 scope global eth0:3232285517
inet 192.168.195.78/32 scope global eth0:3232285518
inet 192.168.195.79/32 scope global eth0:3232285519
inet 192.168.195.80/32 scope global eth0:3232285520
inet6 fe80::a00:27ff:fe76:7529/64 scope link
valid_lft forever preferred_lft forever

The network seems plenty responsive still; and I can ping any of the alias addresses.  Creation of 50,000 aliases took about a minute.  FWIW.

Many of the default Ubuntu desktop themes come with a 1 pixel-wide window border.  This makes it difficult to resize your windows*

You can increase this window size by editing the parameters for your theme.  First off, you need to figure out which theme you’re using.   In many themes, you’ll find this at:
System -> Preferences -> Look and Feel -> Appearance -> Theme tab.

Once you know the theme, open a terminal and edit the file that defines it.  For this example, I’m using the Ambiant-MATE theme with the metacity window manager.  Thus, the file I want to edit is:

/usr/share/themes/Ambiant-MATE/metacity-1/metacity-theme-1.xml

You’ll want to be root to do this.  Look for the frame_geometry_normal section (usually the first), and change these three lines from 1 to a larger value.  I found that 4 pixels is adequate:

<distance name=”left_width” value=”4″/>
<distance name=”right_width” value=”4″/>
<distance name=”bottom_height” value=”4″/>

Save the file, then you need to log out and log back in so your window manager restarts.  That’s it!

*Unless you use the Alt + Right-Mouse-Button or Alt-F8 tricks, but those are not commonly known.

Is there a standard or convention that specifies the long-form option negation prefix for a CLI?  That is, which is correct?:

  --nodaemonize
  --no-daemonize

I looked thru the POSIX specs, the Getopt::Long parsers, the manpages for getopt() and getopts(), and found nada!  So what’s a coder to do?  Write a Perl script, of course!  I wrote script that parsed thru the entire man(1) set of pages, and pulled out both forms of negated long options.  Here’s the result:

  Without dash (no):  368 unique options
  With dash (no-):   1135 unique options

And the winner is… BOTH forms!  There is no standard for it. The with-dash form was preferred 3:1, but that’s not enough margin to call it a clear winner.

What was apparent is for a single utility, use ONE OR THE OTHER.  Don’t ever mix them for a single utility.  And there you have it.

== DRAFT ==

Although there’s no need for a standard usage of the getopt() long options, we have only 2 x 26 = 52 available switch characters for the older short options.  (Actually, more, ‘cuz we can do things like -4 or -# or -@ for switches.  Regardless…)

Because choices are limited, a defacto standard has emerged — 30+ years in the making — for the short options:

  -f   --force, sometimes -f is used for a config file
  -h   --help
  -o   --output (to the named file, for example) (rarely: -o optionname=value)
  -v   --verbose
  -q   --quiet

The above are almost universally used, while the following are “frequently” used:

-a    --all or --append; or a start time (the --at-time)
-c    --configuration-file  or related .conf option, sometimes -f is used for this (but -c preferred)
-d    --debug or  sometimes --directory
-D    --no-daemonize or --disable
-e    --error;  send to stderr instead of syslog
-E    --enable
-g    --group(s)
-i    --interactive, --identity or some identity related thing, sometimes --ignore
-l    --long or --lengthy, such as include details (different than verbose); or --log-level, or --list
-n    --count, any numerical thing
-p    --port or --priority
-r    --recursive
-R    --alternate-root or --root, also -R (uppercase) sometimes used for --recursive
-t    time-related things
-T    test related things, especially test timeouts
-u    --user or username or submitter things, sometimes -l used for this (think l = login name)
-V    --version (uses uppercase V because lowercase v means verbose)
-w    a web-related thing, such as a URL
-x and -X    X11 things.  Historically, the upper/lowercase meaning is reversed; 
        lower is disable and upper is enable it -- this is opposite normal convention.
-y    --yes, take the affirmative or default action instead of prompting; also -y used to mean syslog
-z    --colorize-output
-4    IPv4
-6    IPv6
-#    Any numerical limit  (avoid this tho, it causes problems in shell scripts)

And a defacto convention is that the lowercase form is used to invoke an action, while the uppercase form is used to suppress an action.  For example,

 -z (lowercase) typically means to colorize the output
 -Z (uppercase) means to NOT colorize the output, implying it's colorized by default.

But uppercase can also have conventional meanings, too.  Such as -R for an alternate root.

—

These aren’t absolute, and there’s plenty of commands that don’t follow the above, but there’s more that do.  If you’re writing a new utility or command, please try to follow the above!  The community will thank you!