Technology – Page 5

Ubuntu 20.04
I bought a laptop recently. HP 14 A4 8GB 256GB SSD. It came with Windows 10 and was bundled with so many applications, I didn’t want to use. I tried to install it via PXE. But I couldn’t get that working. Finally, I decided to buy a USB drive and install Ubuntu.

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I have to start with the installation. Ubuntu Desktop version has a minimal option. I would say that it is a brilliant option. It doesn’t bundle office or anything else I don’t want to use. If I want I can download them always. Ubuntu 20.04 has a lovely OEM splash screen. I usually turn off Plymouth, but I decided to leave it on just to see the beautiful OEM logo.

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I installed Numix icons which is part of the main repository which is great again. Widely used applications are included in the main repository. I hate adding new repositories because it slows-down apt update. I heard in a podcast that even Canonical is annoyed by PPAs.

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I like the dark theme. So I didn’t install the Numix dark theme. But you might need to change the color scheme in the text editor if you switch to dark mode.

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Overall I love Ubuntu! (Even though I use a Mac at work) Things have gotten much better and it is quite fun to use. Try the new version and spread the word!

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- linux
- ubuntu
- laptop
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Debug bash scripts

One day, I had to go through a large bash script and create a Debian package for our system. It could have been a strenuous job if I had to understand it. I was lazy to read it. So I found an easy way to get all the steps. I downloaded this on a container and ran with bash -x.

# wget https://download.vividcortex.com/installn--2020-05-20 16:24:06--  https://download.vividcortex.com/installnResolving download.vividcortex.com (download.vividcortex.com)... 13.33.243.45, 13.33.243.100, 13.33.243.16, ...nConnecting to download.vividcortex.com (download.vividcortex.com)|13.33.243.45|:443... connected.nHTTP request sent, awaiting response... 200 OKnLength: 45048 (44K) [application/octet-stream]nSaving to: 'install'nninstall                  100%[==================================>]  43.99K  --.-KB/s    in 0.06s   nn2020-05-20 16:24:07 (732 KB/s) - 'install' saved [45048/45048]nn# lsninstalln# bash -x install n+ VERSION=1.8.159n+ baseuri=https://download.vividcortex.comn+ set -un+ POSIXLY_CORRECT=1n+ export POSIXLY_CORRECTn+ TERM=dumbn+ export TERMn+ unalias -an+ defaultconfdir=/etc/vividcortexn+ confdir=/etc/vividcortexn+ logdir=/var/log/vividcortexn+ runvdir=/var/run/vividcortexn+ superpid=/var/run/vc-agent-007.pidn+ tempdir=n+ socks5=n+ SKIPCERTS=n+ LOADCERTS=n+ EXISTS='command -v'n+ command -v lsn+ command -v lsn+ test https://download.vividcortex.com = unknownn++ id -un+ '[' 0 -ne 0 ']'n+ test -d /usrn+ exitcode=4n+ '[' 4 -eq 4 ']'n++ getopt -o hslkbup:t:v:i:a:c:d:g: -l help,autostart,no-autostart,start-now,load-certs,skip-certs,batch,static,uninstall,delete,debug,off-host,update-init,static-ip,dyn-sample-text,no-proxy,proxy:,token:,version:,init:,sample:,api-uri:,cdn-uri:,bin-dir:,cfg-dir:,aggr-uri:,hostname:,host-tags: -n install --n+ GETARGS=' --'n+ test 0 -eq 0n+ eval set -- ' --'n++ set -- --n+ AUTOSTART=n...n

You can use this if you want to debug or understand a shell script. But of course, you should be able to run it to test.

PostgreSQL 12 – pset format option

Postgres 12 has introduced a new format in psql CLI. There are 9 types available. They are listed below.

aligned

asciidoc

html

latex

latex-longtable

troff-ms

unaligned

wrapped

For more information look -> https://www.postgresql.org/docs/12/app-psql.html

Let’s check each format. An example of aligned is shown here. This is not good with a wide table/output. It can overflow. Less readable. This is the default format.

blipsnchitz=# \pset format alignednOutput format is aligned.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n          name           |  setting   | unit |              category               |                              short_desc                              n-------------------------+------------+------+-------------------------------------+----------------------------------------------------------------------n allow_system_table_mods | off        |      | Developer Options                   | Allows modifications of the structure of system tables.n application_name        | psql       |      | Reporting and Logging / What to Log | Sets the application name to be reported in statistics and logs.n archive_cleanup_command |            |      | Write-Ahead Log / Archive Recovery  | Sets the shell command that will be executed at every restart point.n archive_command         | (disabled) |      | Write-Ahead Log / Archiving         | Sets the shell command that will be called to archive a WAL file.n archive_mode            | off        |      | Write-Ahead Log / Archiving         | Allows archiving of WAL files using archive_command.n(5 rows)nnblipsnchitz=# n

unaligned doesn’t use tabs. Hard to read.

blipsnchitz=# \pset format unalignednOutput format is unaligned.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;nname|setting|unit|category|short_descnallow_system_table_mods|off||Developer Options|Allows modifications of the structure of system tables.napplication_name|psql||Reporting and Logging / What to Log|Sets the application name to be reported in statistics and logs.narchive_cleanup_command|||Write-Ahead Log / Archive Recovery|Sets the shell command that will be executed at every restart point.narchive_command|(disabled)||Write-Ahead Log / Archiving|Sets the shell command that will be called to archive a WAL file.narchive_mode|off||Write-Ahead Log / Archiving|Allows archiving of WAL files using archive_command.n(5 rows)nblipsnchitz=# n

wrapped is useful if your table fit into your terminal width. Otherwise, it does poorly.

blipsnchitz=# \pset format wrappednOutput format is wrapped.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n         name         | setting | unit |            category            |                  short_desc                   n----------------------+---------+------+--------------------------------+-----------------------------------------------n allow_system_table_m.| off     |      | Developer Options              | Allows modifications of the structure of syst.n.ods                  |         |      |                                |.em tables.n application_name     | psql    |      | Reporting and Logging / What t.| Sets the application name to be reported in s.n                      |         |      |.o Log                          |.tatistics and logs.n archive_cleanup_comm.|         |      | Write-Ahead Log / Archive Reco.| Sets the shell command that will be executed .n.and                  |         |      |.very                           |.at every restart point.n archive_command      | (disabl.|      | Write-Ahead Log / Archiving    | Sets the shell command that will be called to.n                      |.ed)     |      |                                |. archive a WAL file.n archive_mode         | off     |      | Write-Ahead Log / Archiving    | Allows archiving of WAL files using archive_c.n                      |         |      |                                |.ommand.n(5 rows)nnblipsnchitz=# n

This is the flashy new feature. I love it! It can be used to export too! Follows the RFC 4180.

blipsnchitz=# \pset format csvnOutput format is csv.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;nname,setting,unit,category,short_descnallow_system_table_mods,off,,Developer Options,Allows modifications of the structure of system tables.napplication_name,psql,,Reporting and Logging / What to Log,Sets the application name to be reported in statistics and logs.narchive_cleanup_command,,,Write-Ahead Log / Archive Recovery,Sets the shell command that will be executed at every restart point.narchive_command,(disabled),,Write-Ahead Log / Archiving,Sets the shell command that will be called to archive a WAL file.narchive_mode,off,,Write-Ahead Log / Archiving,Allows archiving of WAL files using archive_command.nblipsnchitz=# n

psql supports few markup languages. An example of html is shown here.

blipsnchitz=# \pset format htmlnOutput format is html.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n<table border="1">n  <tr>n    <th align="center">name</th>n    <th align="center">setting</th>n    <th align="center">unit</th>n    <th align="center">category</th>n    <th align="center">short_desc</th>n  </tr>n  <tr valign="top">n    <td align="left">allow_system_table_mods</td>n    <td align="left">off</td>n    <td align="left">&nbsp; </td>n    <td align="left">Developer Options</td>n    <td align="left">Allows modifications of the structure of system tables.</td>n  </tr>n  <tr valign="top">n    <td align="left">application_name</td>n    <td align="left">psql</td>n    <td align="left">&nbsp; </td>n    <td align="left">Reporting and Logging / What to Log</td>n    <td align="left">Sets the application name to be reported in statistics and logs.</td>n  </tr>n  <tr valign="top">n    <td align="left">archive_cleanup_command</td>n    <td align="left">&nbsp; </td>n    <td align="left">&nbsp; </td>n    <td align="left">Write-Ahead Log / Archive Recovery</td>n    <td align="left">Sets the shell command that will be executed at every restart point.</td>n  </tr>n  <tr valign="top">n    <td align="left">archive_command</td>n    <td align="left">(disabled)</td>n    <td align="left">&nbsp; </td>n    <td align="left">Write-Ahead Log / Archiving</td>n    <td align="left">Sets the shell command that will be called to archive a WAL file.</td>n  </tr>n  <tr valign="top">n    <td align="left">archive_mode</td>n    <td align="left">off</td>n    <td align="left">&nbsp; </td>n    <td align="left">Write-Ahead Log / Archiving</td>n    <td align="left">Allows archiving of WAL files using archive_command.</td>n  </tr>n</table>n<p>(5 rows)<br />n</p>nblipsnchitz=# n

asciidoc is shown here.

blipsnchitz=# \pset format asciidocnOutput format is asciidoc.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;nn[options="header",cols="<l,<l,<l,<l,<l",frame="none"]n|====n^l|name ^l|setting ^l|unit ^l|category ^l|short_descn|allow_system_table_mods |off |  |Developer Options |Allows modifications of the structure of system tables.n|application_name |psql |  |Reporting and Logging / What to Log |Sets the application name to be reported in statistics and logs.n|archive_cleanup_command |  |  |Write-Ahead Log / Archive Recovery |Sets the shell command that will be executed at every restart point.n|archive_command |(disabled) |  |Write-Ahead Log / Archiving |Sets the shell command that will be called to archive a WAL file.n|archive_mode |off |  |Write-Ahead Log / Archiving |Allows archiving of WAL files using archive_command.n|====nn....n(5 rows)n....nblipsnchitz=# n

latex looks like this.

blipsnchitz=# \pset format latexnOutput format is latex.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n\begin{tabular}{l | l | l | l | l}n\textit{name} & \textit{setting} & \textit{unit} & \textit{category} & \textit{short\_desc} \\n\hlinenallow\_system\_table\_mods & off &  & Developer Options & Allows modifications of the structure of system tables. \\napplication\_name & psql &  & Reporting and Logging / What to Log & Sets the application name to be reported in statistics and logs. \\narchive\_cleanup\_command &  &  & Write-Ahead Log / Archive Recovery & Sets the shell command that will be executed at every restart point. \\narchive\_command & (disabled) &  & Write-Ahead Log / Archiving & Sets the shell command that will be called to archive a WAL file. \\narchive\_mode & off &  & Write-Ahead Log / Archiving & Allows archiving of WAL files using archive\_command. \\n\end{tabular}nn\noindent (5 rows) \\nnblipsnchitz=# n

latex-longtable uses different packages.

blipsnchitz=# \pset format latex-longtablenOutput format is latex-longtable.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n\begin{longtable}{l | l | l | l | l}n\small\textbf{\textit{name}} & \small\textbf{\textit{setting}} & \small\textbf{\textit{unit}} & \small\textbf{\textit{category}} & \small\textbf{\textit{short\_desc}} \\n\midrulen\endfirstheadn\small\textbf{\textit{name}} & \small\textbf{\textit{setting}} & \small\textbf{\textit{unit}} & \small\textbf{\textit{category}} & \small\textbf{\textit{short\_desc}} \\n\midrulen\endheadn\raggedright{allow\_system\_table\_mods}n&n\raggedright{off}n&n\raggedright{}n&n\raggedright{Developer Options}n&n\raggedright{Allows modifications of the structure of system tables.} \tabularnewlinen\raggedright{application\_name}n&n\raggedright{psql}n&n\raggedright{}n&n\raggedright{Reporting and Logging / What to Log}n&n\raggedright{Sets the application name to be reported in statistics and logs.} \tabularnewlinen\raggedright{archive\_cleanup\_command}n&n\raggedright{}n&n\raggedright{}n&n\raggedright{Write-Ahead Log / Archive Recovery}n&n\raggedright{Sets the shell command that will be executed at every restart point.} \tabularnewlinen\raggedright{archive\_command}n&n\raggedright{(disabled)}n&n\raggedright{}n&n\raggedright{Write-Ahead Log / Archiving}n&n\raggedright{Sets the shell command that will be called to archive a WAL file.} \tabularnewlinen\raggedright{archive\_mode}n&n\raggedright{off}n&n\raggedright{}n&n\raggedright{Write-Ahead Log / Archiving}n&n\raggedright{Allows archiving of WAL files using archive\_command.} \tabularnewlinen\end{longtable}nblipsnchitz=# n

troff-ms is the format used in man pages.

blipsnchitz=# \pset format troff-msnOutput format is troff-ms.nblipsnchitz=# nblipsnchitz=# SELECT name, setting, unit, category, short_desc FROM pg_settings LIMIT 5;n.LPn.TSncenter;nl | l | l | l | l.n\fIname\fP	\fIsetting\fP	\fIunit\fP	\fIcategory\fP	\fIshort_desc\fPn_nallow_system_table_mods	off		Developer Options	Allows modifications of the structure of system tables.napplication_name	psql		Reporting and Logging / What to Log	Sets the application name to be reported in statistics and logs.narchive_cleanup_command			Write-Ahead Log / Archive Recovery	Sets the shell command that will be executed at every restart point.narchive_command	(disabled)		Write-Ahead Log / Archiving	Sets the shell command that will be called to archive a WAL file.narchive_mode	off		Write-Ahead Log / Archiving	Allows archiving of WAL files using archive_command.n.TEn.DS Ln(5 rows)n.DEnblipsnchitz=# n

pgloader: Migrating a table from MySQL/MariaDB to PostgreSQL

pgloader is a helpful tool if you want to migrate tables from MySQL/MariaDB to Postgres. This works with AWS RDS instances too.


LOAD DATABASE
     FROM mysql://<mysql_user>:<mysql_password>@<mysql_host>/<source_databases>
     INTO pgsql://<postgres_user>:<postgres_password>@<postgres_host>/<target_database>

  WITH INCLUDE DROP, CREATE TABLES

  SET search_path to 'public'

  INCLUDING ONLY TABLE NAMES MATCHING 'sample_table'

  ALTER TABLE NAMES MATCHING 'sample_table' RENAME TO 'tmp_sample_table'
  ALTER SCHEMA '<source_databases>' RENAME TO 'public';

Let’s say we need to migrate the user table from MySQL to PostgreSQL. Your pgloader file would look like below.

LOAD DATABASE
     FROM mysql://root:Password123@mysqldb.example.com/real_db
     INTO pgsql://postgres:Password456@pgserver101.example.com/adventure_db

  WITH include drop, create tables

  SET search_path to 'public'

  INCLUDING ONLY TABLE NAMES MATCHING 'user'

  ALTER TABLE NAMES MATCHING 'user' RENAME TO 'account'
  ALTER SCHEMA 'real_db' RENAME TO 'public';

You can use the below command to start the migration

$ pgload user.load

Dedunu

Ubuntu 20.04

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Debug bash scripts

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PostgreSQL 12 – pset format option

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pgloader: Migrating a table from MySQL/MariaDB to PostgreSQL

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