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3 files changed, 180 insertions, 371 deletions

diff --git a/content/md/gemfeed/2015-12-05-run-debian-on-your-phone-with-debroid.md b/content/md/gemfeed/2015-12-05-run-debian-on-your-phone-with-debroid.md
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@@ -0,0 +1,180 @@
+# Run Debian on your phone with Debroid
+
+```
+ ____       _               _     _ 
+|  _ \  ___| |__  _ __ ___ (_) __| |
+| | | |/ _ \ '_ \| '__/ _ \| |/ _` |
+| |_| |  __/ |_) | | | (_) | | (_| |
+|____/ \___|_.__/|_|  \___/|_|\__,_|
+                                    
+```
+
+> Written by Paul Buetow 2015-12-05, last updated 2021-05-16
+
+You can use the following tutorial to install a full-blown Debian GNU/Linux Chroot on a LG G3 D855 CyanogenMod 13 (Android 6). First of all you need to have root permissions on your phone and you also need to have the developer mode activated. The following steps have been tested on Linux (Fedora 23).
+
+[![./2015-12-05-run-debian-on-your-phone-with-debroid/Deboroid.png](./2015-12-05-run-debian-on-your-phone-with-debroid/Deboroid.png)](./2015-12-05-run-debian-on-your-phone-with-debroid/Deboroid.png)  
+
+## Foreword
+
+A couple of years have passed since I last worked on Debroid. At the moment I am using the Termux app on Android, which is less sophisticated than a fully blown Debian installation, but sufficient for my current requirements.
+
+## Step by step guide
+
+All scripts mentioned here can be found on GitHub at:
+
+[https://github.com/snonux/debroid](https://github.com/snonux/debroid)  
+
+### First debootstrap stage
+
+This is to be performed on a Fedora Linux machine (could work on a Debian too, but Fedora is just what I use on my personal Laptop). The following steps prepare an initial Debian base image, which then later can be transferred to the phone.
+
+```code
+sudo dnf install debootstrap
+# 5g
+dd if=/dev/zero of=jessie.img bs=$[ 1024 * 1024 ] \
+  count=$[ 1024 * 5 ]
+
+# Show used loop devices
+sudo losetup -f
+# Store the next free one to $loop
+loop=loopN
+sudo losetup /dev/$loop jessie.img
+
+mkdir jessie
+sudo mkfs.ext4 /dev/$loop
+sudo mount /dev/$loop jessie
+sudo debootstrap --foreign --variant=minbase \
+  --arch armel jessie jessie/ \
+  http://http.debian.net/debian
+sudo umount jessie
+```
+
+### Copy Debian image to the phone
+
+Now setup the Debian image on an external SD card on the Phone via Android Debugger as follows:
+
+```
+adb root && adb wait-for-device && adb shell
+mkdir -p /storage/sdcard1/Linux/jessie
+exit
+
+# Sparse image problem, may be too big for copying otherwise
+gzip jessie.img
+# Copy over
+adb push jessie.img.gz /storage/sdcard1/Linux/jessie.img.gz
+adb shell
+cd /storage/sdcard1/Linux
+gunzip jessie.img.gz
+
+# Show used loop devices
+losetup -f
+# Store the next free one to $loop
+loop=loopN
+
+# Use the next free one (replace the loop number)
+losetup /dev/block/$loop $(pwd)/jessie.img
+mount -t ext4 /dev/block/$loop $(pwd)/jessie
+
+# Bind-Mound proc, dev, sys`
+busybox mount --bind /proc $(pwd)/jessie/proc
+busybox mount --bind /dev $(pwd)/jessie/dev
+busybox mount --bind /dev/pts $(pwd)/jessie/dev/pts
+busybox mount --bind /sys $(pwd)/jessie/sys
+
+# Bind-Mound the rest of Android
+mkdir -p $(pwd)/jessie/storage/sdcard{0,1}
+busybox mount --bind /storage/emulated \
+  $(pwd)/jessie/storage/sdcard0
+busybox mount --bind /storage/sdcard1 \
+  $(pwd)/jessie/storage/sdcard1
+
+# Check mounts
+mount | grep jessie
+```
+
+### Second debootstrap stage
+
+This is to be performed on the Android phone itself (inside a Debian chroot):
+
+```
+chroot $(pwd)/jessie /bin/bash -l
+export PATH=/bin:/usr/bin:/usr/local/bin:/sbin:/usr/sbin:/usr/local/sbin
+/debootstrap/debootstrap --second-stage
+exit # Leave chroot
+exit # Leave adb shell
+```
+
+### Setup of various scripts
+
+jessie.sh deals with all the loopback mount magic and so on. It will be run later every time you start Debroid on your phone.
+
+```
+# Install script jessie.sh
+adb push storage/sdcard1/Linux/jessie.sh /storage/sdcard/Linux/jessie.sh
+adb shell
+cd /storage/sdcard1/Linux
+sh jessie.sh enter
+
+# Bashrc
+cat <<END >~/.bashrc
+export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$PATH
+export EDITOR=vim
+hostname $(cat /etc/hostname)
+END
+
+# Fixing an error message while loading the profile
+sed -i s#id#/usr/bin/id# /etc/profile
+
+# Setting the hostname
+echo phobos > /etc/hostname
+echo 127.0.0.1 phobos > /etc/hosts
+hostname phobos
+
+# Apt-sources
+cat <<END > sources.list
+deb http://ftp.uk.debian.org/debian/ jessie main contrib non-free
+deb-src http://ftp.uk.debian.org/debian/ jessie main contrib non-free
+END
+apt-get update
+apt-get upgrade
+apt-get dist-upgrade
+exit # Exit chroot
+```
+
+### Entering Debroid and enable a service
+
+This enters Debroid on your phone and starts the example service uptimed:
+
+```
+sh jessie.sh enter
+
+# Setup example serice uptimed
+apt-get install uptimed
+cat <<END > /etc/rc.debroid
+export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:$PATH
+service uptimed status &>/dev/null || service uptimed start
+exit 0
+END
+
+chmod 0755 /etc/rc.debroid
+exit # Exit chroot
+exit # Exit adb shell
+```
+
+### Include to Android startup:
+
+I you want to start Debroid automatically every time when your phone starts, then do the following:
+
+```
+adb push data/local/userinit.sh /data/local/userinit.sh
+adb shell
+chmod +x /data/local/userinit.sh
+exit
+```
+
+Reboot & test!  Enjoy!
+
+E-Mail me your thoughts at comments@mx.buetow.org!
+
+[Go back to the main site](../)  
diff --git a/content/md/gemfeed/2015-12-05-run-debian-on-your-phone-with-debroid/Deboroid.png b/content/md/gemfeed/2015-12-05-run-debian-on-your-phone-with-debroid/Deboroid.png
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diff --git a/content/md/gemfeed/2021-05-15-personal-bash-coding-style-guide.draft.md b/content/md/gemfeed/2021-05-15-personal-bash-coding-style-guide.draft.md
deleted file mode 100644
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--- a/content/md/gemfeed/2021-05-15-personal-bash-coding-style-guide.draft.md
+++ /dev/null
@@ -1,371 +0,0 @@
-# Personal Bash coding style guide
-
-```
-   .---------------------------.
-  /,--..---..---..---..---..--. `.
- //___||___||___||___||___||___\_|
- [j__ ######################## [_|
-    \============================|
- .==|  |"""||"""||"""||"""| |"""||
-/======"---""---""---""---"=|  =||
-|____    []*          ____  | ==||
-//  \\               //  \\ |===||  hjw
-"\__/"---------------"\__/"-+---+'
-```                     
-
-> Written by Paul Buetow 2021-05-16
-
-Lately, I have been polishing and writing a lot of Bash code. Not that I never wrote a lot of Bash, but now as I also looked through the "Google Shell Style Guide" I thought it is time to also write my own thoughts on that. I agree to that guide in most, but not in all points. 
-
-[Google Shell Style Guide](https://google.github.io/styleguide/shellguide.html)  
-
-## My modifications
-
-These are my personal modifications of the Google Guide.
-
-### 2 space soft-tabs indentation
-
-I know there have been many tab- and soft-tab wars on this planet. Google recommends to use 2 space soft-tabs for Bash scripts. 
-
-I personally don't really care if I use 2 or 4 space indentations. I agree however that tabs should not be used. I personally tend to use 4 space soft-tabs as that's currently how my Vim is configured for any programming language. What matters most though is consistency within the same script/project.
-
-Google also recommends limiting the line length to 80 characters. For some people that seem's to be an ancient habit from the 80's, where all computer terminals couldn't display longer lines. But I think that the 80 character mark is still a good practice at least for shell scripts. For example, I am often writing code on a Microsoft Go Tablet PC (running Linux of course) and it comes in very handy if the lines are not too long due to the relatively small display on the device.
-
-I hit the 80 character line length quicker with the 4 spaces than with 2 spaces, but that makes me refactor the Bash code more aggressively which is actually a good thing. 
-
-### Breaking long pipes
-
-Google recommends to break up long pipes like this:
-
-```
-# All fits on one line
-command1 | command2
-
-# Long commands
-command1 \
-  | command2 \
-  | command3 \
-  | command4
-```
-
-I think there is a better way like the following, which is less noisy. The pipe | already indicates the Bash that another command is expected, thus making the explicit line breaks with \ obsolete:
-
-```
-# Long commands
-command1 |
-    command2 |
-    command3 |
-    command4
-```
-
-### Quoting your variables
-
-Google recommends to always quote your variables. I think generally you should do that only for variables where you are unsure about the content/values of the variables (e.g. content is from an external input source and may contains whitespace or other special characters). In my opinion, the code will become quite noisy when you always quote your variables like this:
-
-```
-greet () {
-    local -r greeting="${1}"
-    local -r name="${2}"
-    echo "${greeting} ${name}!"
-}
-```
-
-In this particular example I agree that you should quote them as you don't really know what is the input (are there for example whitespace characters?). But if you are sure that you are only using simple bare words then I think that the code looks much cleaner when you do this instead:
-
-```
-say_hello_to_paul () {
-    local -r greeting=Hello
-    local -r name=Paul
-    echo "$greeting $name!"
-}
-```
-
-You see I also omitted the curly braces { } around the variables. I only use the curly braces around variables when it makes the code either easier/clearer to read or if it is necessary to use them:
-
-```
-declare FOO=bar
-# Curly braces around FOO are necessary
-echo "foo${FOO}baz"
-```
-
-A few more words on always quoting the variables: For the sake of consistency (and for the sake of making ShellCheck happy) I am not against quoting everything I encounter. I personally also think that the larger the Bash script becomes, the more important it becomes to always quote variables. That's because it will be more likely that you might not remember that some of the functions don't work on values with spaces in it for example.  It's just that I won't quote everything in every small script I write. 
-
-### Prefer builtin commands over external commands
-
-Google recommends using the builtin commands over external available commands where possible:
-
-```
-# Prefer this:
-addition=$(( X + Y ))
-substitution="${string/#foo/bar}"
-
-# Instead of this:
-addition="$(expr "${X}" + "${Y}")"
-substitution="$(echo "${string}" | sed -e 's/^foo/bar/')"
-```
-
-I don't agree fully here. The external commands (especially sed) are much more sophisticated and powerful than the Bash builtin versions. Sed can do much more than the Bash can ever do natively when it comes to text manipulation (the name "sed" stands for streaming editor after all).
-
-I prefer to do light text processing with the Bash builtins and more complicated text processing with external programs such as sed, grep, awk, cut and tr. There is however also the case of medium-light text processing where I would want to use external programs too. That is so because I remember using them better than the Bash builtins. The Bash can get quite obscure here (even Perl will be more readable then - Side note: I love Perl).
-
-Also, you would like to use an external command for floating-point calculation (e.g. bc) instead using the Bash builtins (worth noticing that ZSH supports builtin floating-points).
-
-I even didn't get started what you can do with Awk (especially GNU Awk), a fully fledged programming language. Tiny Awk snippets tend to be used quite often in Shell scripts without respecting the real power of Awk. But if you did everything in Perl or Awk or another scripting language, then it wouldn't be a Bash script anymore, wouldn't it? ;-)
-
-## My additions
-
-### Use of 'yes' and 'no'
-
-Bash does not support a boolean type. I tend to just use the strings 'yes' and 'no' here. For some time I used 0 for false and 1 for true, but I think that the yes/no strings are easier to read. Yes, the Bash script would need to perform string comparisons on every check, but if performance is important to you, you wouldn't want to use a Bash script anyway, correct?
-
-```
-declare -r SUGAR_FREE=yes
-declare -r I_NEED_THE_BUZZ=no
-
-buy_soda () {
-    local -r sugar_free=$1
-
-    if [[ $sugar_free == yes ]]; then
-        echo 'Diet Dr. Pepper'
-    else
-        echo 'Pepsi Coke'
-    fi
-}
-
-buy_soda $I_NEED_THE_BUZZ
-```
-
-### Non-evil alternative to variable assignments via eval
-
-Google is in the opinion that eval should be avoided. I think so too. They list this example in their guide:
-
-```
-# What does this set?
-# Did it succeed? In part or whole?
-eval $(set_my_variables)
-
-# What happens if one of the returned values has a space in it?
-variable="$(eval some_function)"
-
-```
-
-However, if I want to read variables from another file I don't have to use eval here. I just source the file:
-
-```
-% cat vars.source.sh
-declare foo=bar
-declare bar=baz
-declare bay=foo
-
-% bash -c 'source vars.source.sh; echo $foo $bar $baz'
-bar baz foo
-```
-
-And if I want to assign variables dynamically then I could just run an external script and source its output (This is how you could do metaprogramming in Bash - write code which produces code for immediate execution):
-
-```
-% cat vars.sh
-#!/usr/bin/bash
-cat <<END
-declare date="$(date)"
-declare user=$USER
-END
-
-% bash -c 'source <(./vars.sh); echo "Hello $user, it is $date"'
-Hello paul, it is Sat 15 May 19:21:12 BST 2021
-```
-
-The downside is that ShellCheck won't be able to follow the dynamic sourcing anymore.
-
-### Prefer pipes over arrays for list processing
-
-When I do list processing in Bash, I prefer to use pipes. You can chain then through Bash functions as well which is pretty neat. Usually my list processing scripts are of a structure similar to the following example:
-
-```
-filter_lines () {
-    echo 'Start filtering lines in a fancy way!' >&2
-    grep ... | sed ....
-}
-
-process_lines () {
-    echo 'Start processing line by line!' >&2
-    while read -r line; do
-        ... do something and produce a result...
-        echo "$result"
-    done 
-}
-
-# Do some post processing of the data
-postprocess_lines () {
-    echo 'Start removing duplicates!' >&2
-    sort -u
-}
-
-genreate_report () {
-    echo 'My boss wants to have a report!' >&2
-    tee outfile.txt
-    wc -l outfile.txt
-}
-
-main () {
-    filter_lines |
-        process_lines |
-        postprocess_lines |
-        generate_report
-}
-
-main
-```
-
-The stdout is always passed as a pipe to the next following stage. The stderr is used for info logging.
-
-### Assign-then-shift
-
-I often refactor existing Bash code. That leads me to adding and removing function arguments quite often. It's quite repetitive work changing the $1, $2.... function argument numbers every time you change the order or add/remove possible arguments.
-
-The solution is to use of the "assign-then-shift"-pattern which goes like this: "local -r var1=$1; shift; local -r var2=$1; shift". The idea is that you only use "$1" to assign function arguments to named (better readable) local function variables. You will never have to bother about "$2" or above. That is very useful when you constantly refactor your code and remove or add function arguments. It's something what I picked up from a colleague (a pure Bash wizard) some time ago:
-
-```
-some_function () {
-    local -r param_foo="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
-}
-```
-
-Want to add a param_baz? Just do this:
-
-```
-some_function () {
-    local -r param_foo="$1"; shift
-    local -r param_bar="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
-}
-```
-
-Want to remove param_foo? Nothing easier than that:
-
-```
-some_function () {
-    local -r param_bar="$1"; shift
-    local -r param_baz="$1"; shift
-    local -r param_bay="$1"; shift
-    ...
-}
-```
-
-As you can see I didn't need to change any other assignments within the function.
-
-### Paranoid mode
-
-I call this the paranoid mode. The Bash will stop executing when a command exists with a status not equal to 0:
-
-```
-set -e
-grep -q foo <<< bar
-echo Jo
-```
-
-Here 'Jo' will never be printed out as the grep didn't find any match. It's unrealistic for most scripts to purely run in paranoid mode so there must be a way to add exceptions. Critical Bash scripts of mine tend to look like this:
-
-```
-#!/bin/bash
-
-set -e
-
-some_function () {
-    .. some critical code
-    ...
-
-    set +e
-    # Grep might fail, but that's OK now
-    grep ....
-    local -i ec=$?
-    set -e
-
-    .. critical code continues ...
-    if [[ $ec -ne 0 ]]; then
-        ...
-    fi
-    ...
-}
-```
-
-## Learned
-
-There are also a couple of things I've learned from Googles guide.
-
-### Unintended lexicographical comparison.
-
-The following looks like valid Bash code:
-
-```
-if [[ "${my_var}" > 3 ]]; then
-    # True for 4, false for 22.
-    do_something
-fi
-```
-
-... but is Probably unintended lexicographical comparison. A correct way would be:
-
-```
-if (( my_var > 3 )); then
-    do_something
-fi
-```
-
-or
-
-```
-if [[ "${my_var}" -gt 3 ]]; then
-    do_something
-fi
-```
-
-### PIPESTATUS
-
-To be honest, I have never used the PIPESTATUS variable before. I knew that it's there, but I never bothered to fully understand it until now.
-
-The PIPESTATUS variable in Bash allows checking of the return code from all parts of a pipe. If it’s only necessary to check success or failure of the whole pipe, then the following is acceptable:
-
-```
-tar -cf - ./* | ( cd "${dir}" && tar -xf - )
-if (( PIPESTATUS[0] != 0 || PIPESTATUS[1] != 0 )); then
-    echo "Unable to tar files to ${dir}" >&2
-fi
-```
-
-However, as PIPESTATUS will be overwritten as soon as you do any other command, if you need to act differently on errors based on where it happened in the pipe, you’ll need to assign PIPESTATUS to another variable immediately after running the command (don’t forget that [ is a command and will wipe out PIPESTATUS).
-
-```
-tar -cf - ./* | ( cd "${DIR}" && tar -xf - )
-return_codes=( "${PIPESTATUS[@]}" )
-if (( return_codes[0] != 0 )); then
-    do_something
-fi
-if (( return_codes[1] != 0 )); then
-    do_something_else
-fi
-```
-
-## Use common sense and BE CONSISTENT.
-
-The following 2 paragraphs are completely quoted from the Google guidelines. But they hit the hammer on the head:
-
-> If you are editing code, take a few minutes to look at the code around you and determine its style. If they use spaces around their if clauses, you should, too. If their comments have little boxes of stars around them, make your comments have little boxes of stars around them too.
-
-> The point of having style guidelines is to have a common vocabulary of coding so people can concentrate on what you are saying, rather than on how you are saying it. We present global style rules here so people know the vocabulary. But local style is also important. If code you add to a file looks drastically different from the existing code around it, the discontinuity throws readers out of their rhythm when they go to read it. Try to avoid this.
-
-
-## Advanced Bash learning pro tip
-
-I also highly recommend having a read through the "Advanced Bash-Scripting Guide" (which is not from Google). I use it as the universal Bash reference and learn something new every time I have a look at it.
-
-[Advanced Bash-Scripting Guide](https://tldp.org/LDP/abs/html/)  
-
-E-Mail me your thoughts at comments@mx.buetow.org!
-
-[Go back to the main site](../)