在Docker Hub下载的CentOS镜像没有Network组件，而且不可以自己定制，我们为了解决这个问题，需要创建自己的CentOS镜像，并对其进行定制。本文使用CentOS的ISO文件生成用于OpenStack的image文件，并使用该image生成Docker的image文件。
1 Prepare
We have installed the virt-manager on CentOS7-mini. We use virt-manager to install the ISO, and then generate the centos7.img, which is the full disk of VM.
1.1 Install VM via virt-manager
You should take attention on the follow step.
(1) We choose [Local install media (ISO image or CDROM)] to install the operating system on VM.
(2) Then choose [Use ISO image], and click [Browse...] to find the volume. Select Linux as OS type and select the fit Version.
(3) If has no the storage pool, you can click [+] on the left low to create a folder as the storage pool.
(4) We should create the vm in an image file, and use this image for OpenStack. We choose [Enable storage for this virtual machine] and [Select or create custom storage], then click [Manage...] to find the volume.
(5) We can click [+] to create storage volume (centos7.img) in the above storage pool. We select the qcow2 as the storage format to save the disk space and we set the Max Capacity to 100 GiB.
(6) Step by step to create and install VM, and make sure the VM to be working.
1.2 Install some packages on VM
As we know, the CentOS7-mini has few softwares, we can install some packages to enable more function.
1 yum install -y vim wget git net-tools
1.3 Replace the boot efi
To avoid the CentOS boot issue, we should replace /boot/efi/EFI/BOOT/BOOTAA64.EFI via /boot/efi/EFI/centos/grubaa64.efi.
1 cp -f /boot/efi/EFI/centos/grubaa64.efi /boot/efi/EFI/BOOT/BOOTAA64.EFI
2 Create the image for OpenStack
2.1 Convert the image format
The centos7.img is still 100G, we should convert the image format to save the disk space.
1 qemu-img convert -c -O qcow2 centos7.img centos7.qcow2
2.2 Upload the image to OpenStack
1 openstack image create --disk-format qcow2 --container-format bare --public --property hw_firmware_type="uefi" --file centos7.qcow2 centos7.qcow2
3 Create the image for Docker
3.1 Pack the system disk “/”
Docker need the “/” folder of centos as docker images. We use tar to pack the “/” folder.
1 modprobe nbd max_part=16 2 qemu-nbd -c /dev/nbd0 centos7.qcow2 3 mount /dev/ndb0p4 /mnt 4 chroot /mnt bash 5 tar --numeric-owner --exclude=/proc --exclude=/sys -cvf centos7.tar /
3.2 Import the docker image
Import centos as docker image, and use centos7-local to run an container.
1 cat centos7.tar | docker import - centos7-local 2 docker images 3 docker run -d --name "centos7-local" centos7-local /bin/bash 4 docker exec -it centos7-local /bin/bash
4 Create docker image and enable systemctl
4.1 Create image from the iso
# Use local iso as repo
1 wget http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-Minimal-1804.iso 2 mount CentOS-7-x86_64-Minimal-1804.iso /mnt 3 cd /etc/yum.repo.d/ 4 mkdir bak 5 mv *.repo bak/ 6 vim CentOS-Local.repo
1 [CentOS-Local] 2 baseurl = file:///mnt/ 3 gpgcheck = 0 4 enabled = 1 5 name = CentOS-Local
7 yum clean all 8 rm -rf /var/cache/yum
# Create a base CentOS Docker image
1 vim mkimage-yum.sh
1 #!/usr/bin/env bash 2 # 3 # Create a base CentOS Docker image. 4 # 5 # This script is useful on systems with yum installed (e.g., building 6 # a CentOS image on CentOS). See contrib/mkimage-rinse.sh for a way 7 # to build CentOS images on other systems. 8 9 set -e 10 11 usage() { 12 cat <<EOOPTS 13 $(basename $0) [OPTIONS] <name> 14 OPTIONS: 15 -p "<packages>" The list of packages to install in the container. 16 The default is blank. 17 -g "<groups>" The groups of packages to install in the container. 18 The default is "Core". 19 -y <yumconf> The path to the yum config to install packages from. The 20 default is /etc/yum.conf for Centos/RHEL and /etc/dnf/dnf.conf for Fedora 21 EOOPTS 22 exit 1 23 } 24 25 # option defaults 26 yum_config=/etc/yum.conf 27 if [ -f /etc/dnf/dnf.conf ] && command -v dnf &> /dev/null; then 28 yum_config=/etc/dnf/dnf.conf 29 alias yum=dnf 30 fi 31 install_groups="Core" 32 while getopts ":y:p:g:h" opt; do 33 case $opt in 34 y) 35 yum_config=$OPTARG 36 ;; 37 h) 38 usage 39 ;; 40 p) 41 install_packages="$OPTARG" 42 ;; 43 g) 44 install_groups="$OPTARG" 45 ;; 46 ?) 47 echo "Invalid option: -$OPTARG" 48 usage 49 ;; 50 esac 51 done 52 shift $((OPTIND - 1)) 53 name=$1 54 55 if [[ -z $name ]]; then 56 usage 57 fi 58 59 target=$(mktemp -d --tmpdir $(basename $0).XXXXXX) 60 61 set -x 62 63 mkdir -m 755 "$target"/dev 64 mknod -m 600 "$target"/dev/console c 5 1 65 mknod -m 600 "$target"/dev/initctl p 66 mknod -m 666 "$target"/dev/full c 1 7 67 mknod -m 666 "$target"/dev/null c 1 3 68 mknod -m 666 "$target"/dev/ptmx c 5 2 69 mknod -m 666 "$target"/dev/random c 1 8 70 mknod -m 666 "$target"/dev/tty c 5 0 71 mknod -m 666 "$target"/dev/tty0 c 4 0 72 mknod -m 666 "$target"/dev/urandom c 1 9 73 mknod -m 666 "$target"/dev/zero c 1 5 74 75 # amazon linux yum will fail without vars set 76 if [ -d /etc/yum/vars ]; then 77 mkdir -p -m 755 "$target"/etc/yum 78 cp -a /etc/yum/vars "$target"/etc/yum/ 79 fi 80 81 if [[ -n "$install_groups" ]]; 82 then 83 yum -c "$yum_config" --installroot="$target" --releasever=/ --setopt=tsflags=nodocs 84 --setopt=group_package_types=mandatory -y groupinstall "$install_groups" 85 fi 86 87 if [[ -n "$install_packages" ]]; 88 then 89 yum -c "$yum_config" --installroot="$target" --releasever=/ --setopt=tsflags=nodocs 90 --setopt=group_package_types=mandatory -y install "$install_packages" 91 fi 92 93 yum -c "$yum_config" --installroot="$target" -y clean all 94 95 cat > "$target"/etc/sysconfig/network <<EOF 96 NETWORKING=yes 97 HOSTNAME=localhost.localdomain 98 EOF 99 100 # effectively: febootstrap-minimize --keep-zoneinfo --keep-rpmdb --keep-services "$target". 101 # locales 102 rm -rf "$target"/usr/{{lib,share}/locale,{lib,lib64}/gconv,bin/localedef,sbin/build-locale-archive} 103 # docs and man pages 104 rm -rf "$target"/usr/share/{man,doc,info,gnome/help} 105 # cracklib 106 rm -rf "$target"/usr/share/cracklib 107 # i18n 108 rm -rf "$target"/usr/share/i18n 109 # yum cache 110 rm -rf "$target"/var/cache/yum 111 mkdir -p --mode=0755 "$target"/var/cache/yum 112 # sln 113 rm -rf "$target"/sbin/sln 114 # ldconfig 115 rm -rf "$target"/etc/ld.so.cache "$target"/var/cache/ldconfig 116 mkdir -p --mode=0755 "$target"/var/cache/ldconfig 117 118 version= 119 for file in "$target"/etc/{redhat,system}-release 120 do 121 if [ -r "$file" ]; then 122 version="$(sed 's/^[^0-9]*([0-9.]+).*$/1/' "$file")" 123 break 124 fi 125 done 126 127 if [ -z "$version" ]; then 128 echo >&2 "warning: cannot autodetect OS version, using '$name' as tag" 129 version=$name 130 fi 131 132 tar --numeric-owner -c -C "$target" . | docker import - $name:$version 133 134 docker run -i -t --rm $name:$version /bin/bash -c 'echo success' 135 136 rm -rf "$target"
2 chmod +x mkimage-yum.sh 3 ./mkimage-yum.sh centos-lingmo
4.2 Run docker and enable systemctl
1 docker images 2 docker run -d --privileged=true --name centos-test centos-hxt:7.5.1804 /usr/sbin/init 3 docker exec -it centos-test /bin/bash
Now, you can run systemctl to manage the server on docker vm.
5 Reference
https://github.com/moby/moby/blob/master/contrib/mkimage-yum.sh
https://blog.csdn.net/luckytanggu/article/details/71514798