CentOS Stream 8
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Buildah : Install
2021/03/22
 
Install Buildah that supports to create Container images.
It's possible to create OCI (Open Container Initiative) format image without specific Service Daemon.
[1] Install Buildah.
[root@dlp ~]#
dnf -y install buildah
[2] This is the basic usage for Buildah.
Create a working container from an image.
# create a working container from [centos] image

[root@dlp ~]#
buildah from centos

Resolved "centos" as an alias (/etc/containers/registries.conf.d/shortnames.conf)
Getting image source signatures
...
...
Writing manifest to image destination
Storing signatures
centos-working-container

# show container list

[root@dlp ~]#
buildah containers

CONTAINER ID  BUILDER  IMAGE ID     IMAGE NAME                       CONTAINER NAME
5b03b5f7f695     *     2f3766df23b6 registry.centos.org/centos:la... centos-working-container

# show container image list

[root@dlp ~]#
buildah images

REPOSITORY                   TAG      IMAGE ID       CREATED        SIZE
registry.centos.org/centos   latest   2f3766df23b6   3 months ago   217 MB

# possible to use images on podman

[root@dlp ~]#
podman images

REPOSITORY                  TAG     IMAGE ID      CREATED       SIZE
registry.centos.org/centos  latest  2f3766df23b6  3 months ago  217 MB
[3] Operate Working Container.
# set shell variable

[root@dlp ~]#
container=$(buildah from centos)

[root@dlp ~]#
echo $container

centos-working-container-1
# possible to run commands

[root@dlp ~]#
buildah run $container echo "Hello Buildah World"

Hello Buildah World
[root@dlp ~]#
buildah run $container bash

[root@12ab26f7bd2c /]#
dnf -y install python36

[root@12ab26f7bd2c /]#
[root@dlp ~]#
buildah run $container whereis python3

python3: /usr/bin/python3.6 /usr/bin/python3.6m /usr/bin/python3 /usr/lib/python3.6 /usr/lib64/python3.6 /usr/include/python3.6m /usr/share/man/man1/python3.1.gz
[4] Copy files into Working Container.
[root@dlp ~]#
echo "buildah test" > buildah.txt

[root@dlp ~]#
buildah copy $container buildah.txt /tmp/buildah.txt

7553c62d21edda64a3067fa9805a5cd8e5781c6058be12eb9792d7e0e9781ed4
[root@dlp ~]#
buildah run $container cat /tmp/buildah.txt

buildah test
[5] Mount filesystem of Working Container.
[root@dlp ~]#
buildah mount $container

/var/lib/containers/storage/overlay/afa27e95054ce6a97df933e6bdae66306d67cbfe5a07d676751cacb7f254cb4d/merged
[root@dlp ~]#
ll /var/lib/containers/storage/overlay/afa27e95054ce6a97df933e6bdae66306d67cbfe5a07d676751cacb7f254cb4d/merged

total 0
lrwxrwxrwx. 1 root root  7 Nov  4 00:22 bin -> usr/bin
drwxr-xr-x. 2 root root  6 Dec  5 02:37 dev
drwxr-xr-x. 1 root root 56 Mar 22 11:13 etc
drwxr-xr-x. 2 root root  6 Nov  4 00:22 home
.....
.....

[root@dlp ~]#
buildah umount $container

48fe445847dfdf439059f745ee7f408bb29113f9c82ad2c80ca983d22d30e69f
[6] Create a container image from Working Container.
[root@dlp ~]#
buildah commit $container my-centos:latest

Getting image source signatures
...
...
...
Writing manifest to image destination
Storing signatures
e7ea5d037c9db1049179e1b2874442298c2b119e649b96a33a8ac70bdd46373f

[root@dlp ~]#
buildah images

REPOSITORY                   TAG      IMAGE ID       CREATED          SIZE
localhost/my-centos          latest   e7ea5d037c9d   25 seconds ago   257 MB
registry.centos.org/centos   latest   2f3766df23b6   3 months ago     217 MB

# possible to use container images on podman

[root@dlp ~]#
podman run localhost/my-centos hostname

bac19a070c6d
[7] Push a container image to specified Registry.
[root@dlp ~]#
buildah images

REPOSITORY                   TAG      IMAGE ID       CREATED          SIZE
localhost/my-centos          latest   e7ea5d037c9d   55 seconds ago   257 MB
registry.centos.org/centos   latest   2f3766df23b6   3 months ago     217 MB

# push [localhost/my-centos] image to [node01.srv.world:5000] registry

# if target registry is not on SSL/TLS, need [--tls-verify=false] option

[root@dlp ~]#
buildah push --tls-verify=false localhost/my-centos node01.srv.world:5000/my-centos

Getting image source signatures
...
...
...
Writing manifest to image destination
Storing signatures

[root@dlp ~]#
curl node01.srv.world:5000/v2/_catalog

{"repositories":["my-centos"]}
# possible to Pull from other nodes

[root@node01 ~]#
podman pull --tls-verify=false node01.srv.world:5000/my-centos

[root@node01 ~]#
podman images

REPOSITORY                       TAG     IMAGE ID      CREATED         SIZE
node01.srv.world:5000/my-centos  latest  e7ea5d037c9d  21 minutes ago  257 MB
registry.centos.org/centos       latest  2f3766df23b6  3 months ago    217 MB
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