구차니의 잡동사니 모음

# ll -h

-rw-------. 1 root root 1.1G  6월  3 12:23 generic.qcow2

# file *

generic.qcow2:       QEMU QCOW Image (v3), 1073741824 bytes

# qemu-img resize generic.qcow2 +19G

Image resized.

# ll -h

합계 32G

-rw-------. 1 root root 1.1G  6월  3 12:25 generic.qcow2

# file *

generic.qcow2:       QEMU QCOW Image (v3), 21474836480 bytes

# qemu-img resize generic.qcow2 -19G

qemu-img: qcow2 doesn't support shrinking images yet

qemu-img: This image does not support resize 

이미지는 컨테이너 실행에 필요한 파일과 설정값등을 포함하고 있는 것으로 상태값을 가지지 않고 변하지 않습니다(Immutable). 

컨테이너는 이미지를 실행한 상태라고 볼 수 있고 추가되거나 변하는 값은 컨테이너에 저장됩니다. 

 도커 이미지 생성

$ docker build -t django-sample .

앱 컨테이너를 실행

$ docker run -it --rm \

    -p 8000:8000 \

    django-sample \

    ./manage.py runserver 0:8000

데이터베이스 컨테이너 실행

$ docker run -it --rm \

    postgres:9.6.1

앱 컨테이너를 실행한 후 PostgreSQL 컨테이너를 실행했습니다. 그런데 컨테이너는 실행 직후부터 컨테이너 외부의 상황과 격리됩니다. 따라서 PostgreSQL 컨테이너가 실행되었는지 알지 못하죠.

db 컨테이너를 지우면, 데이터베이스 데이터가 사라짐

docker 단일 컨테이너를 관리합니다.

docker-compose 은 여러 컨테이너 애플리케이션을 관리합니다.

docker-compose의 사용 에는 3 단계가 필요합니다.

Dockerfile을 사용 하여 앱 환경 정의

docker-compose.yml 에 앱 서비스 정의

docker-compose up 실행하여 앱을 시작하고 실행합니다. 

# yum search postgresql

Loaded plugins: fastestmirror, langpacks

Loading mirror speeds from cached hostfile

 * base: mirror.kakao.com

 * extras: mirror.kakao.com

 * updates: mirror.kakao.com

======================================================== N/S matched: postgresql =========================================================

freeradius-postgresql.x86_64 : Postgresql support for freeradius

libreoffice-postgresql.x86_64 : PostgreSQL connector for LibreOffice

pcp-pmda-postgresql.x86_64 : Performance Co-Pilot (PCP) metrics for PostgreSQL

postgresql.i686 : PostgreSQL client programs

postgresql.x86_64 : PostgreSQL client programs

postgresql-contrib.x86_64 : Extension modules distributed with PostgreSQL

postgresql-devel.i686 : PostgreSQL development header files and libraries

postgresql-devel.x86_64 : PostgreSQL development header files and libraries

postgresql-docs.x86_64 : Extra documentation for PostgreSQL

postgresql-jdbc.noarch : JDBC driver for PostgreSQL

postgresql-jdbc-javadoc.noarch : API docs for postgresql-jdbc

postgresql-libs.i686 : The shared libraries required for any PostgreSQL clients

postgresql-libs.x86_64 : The shared libraries required for any PostgreSQL clients

postgresql-odbc.x86_64 : PostgreSQL ODBC driver

postgresql-plperl.x86_64 : The Perl procedural language for PostgreSQL

postgresql-plpython.x86_64 : The Python2 procedural language for PostgreSQL

postgresql-pltcl.x86_64 : The Tcl procedural language for PostgreSQL

postgresql-server.x86_64 : The programs needed to create and run a PostgreSQL server

postgresql-static.i686 : Statically linked PostgreSQL libraries

postgresql-static.x86_64 : Statically linked PostgreSQL libraries

postgresql-test.x86_64 : The test suite distributed with PostgreSQL

postgresql-upgrade.x86_64 : Support for upgrading from the previous major release of PostgreSQL

qt-postgresql.i686 : PostgreSQL driver for Qt's SQL classes

qt-postgresql.x86_64 : PostgreSQL driver for Qt's SQL classes

qt3-PostgreSQL.i686 : PostgreSQL drivers for Qt 3's SQL classes

qt3-PostgreSQL.x86_64 : PostgreSQL drivers for Qt 3's SQL classes

qt5-qtbase-postgresql.i686 : PostgreSQL driver for Qt5's SQL classes

qt5-qtbase-postgresql.x86_64 : PostgreSQL driver for Qt5's SQL classes

PyGreSQL.x86_64 : A Python client library for PostgreSQL

apr-util-pgsql.x86_64 : APR utility library PostgreSQL DBD driver

libdbi-dbd-pgsql.x86_64 : PostgreSQL plugin for libdbi

perl-DBD-Pg.x86_64 : A PostgreSQL interface for perl

php-pgsql.x86_64 : A PostgreSQL database module for PHP

python-psycopg2.x86_64 : A PostgreSQL database adapter for Python

python-psycopg2-debug.x86_64 : A PostgreSQL database adapter for Python 2 (debug build)

python-psycopg2-doc.x86_64 : Documentation for psycopg python PostgreSQL database adapter

redland-pgsql.x86_64 : PostgreSQL storage support for Redland

rhdb-utils.x86_64 : Miscellaneous utilities for PostgreSQL - Red Hat Edition

tcl-pgtcl.x86_64 : A Tcl client library for PostgreSQL

  Name and summary matches only, use "search all" for everything. 

SELECT * FROM pg_catalog.pg_tables; 

SELECT * FROM pg_catalog.pg_tables WHERE tableowner='username;' 

pgAdmin 4 is a complete rewrite of pgAdmin, built using Python and Javascript/jQuery. A desktop runtime written in C++ with Qt allows it to run standalone for individual users, or the web application code may be deployed directly on a webserver for use by one or more users through their web browser. The software has the look and feel of a desktop application whatever the runtime environment is, and vastly improves on pgAdmin III with updated user interface elements, multi-user/web deployment options, dashboards and a more modern design. 

 sudo sh -c 'echo "deb http://apt.postgresql.org/pub/repos/apt/ $(lsb_release -cs)-pgdg main" >> /etc/apt/sources.list.d/pgdg.list'

sudo apt install wget ca-certificates

wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add

sudo apt update

sudo apt install pgadmin4

 docker run 명령이 "create" 와 "start" 명령을 한번에 실행시키는 명령

It turns out, both Linux and Windows now have the ability to use an SSD as a cache for a slower disk. The Linux version is called BCache and has been available since kernel 3.10 (available in Debian Jessie - Testing). 

you can use BCache on Linux to enable caching of the file drive by using your SSD as a cache 

Well, we got a bcache answer but no flashcache answer 

After looking at the samba configuration file I saw that Async IO (AIO) was not enabled by default. What AIO does is that it let’s Samba handle several file operations asynchronously. This can, at the expense of some CPU cycles, increase the performance quite a lot.