The document describes the process of setting up Docker on a 32-bit Debian Wheezy system. The initial Docker installation and image pulls failed with an "exec format error". After researching the issue, it was determined that the kernel needed to be updated to 64-bit. Updating just the kernel to 64-bit resolved the incompatibility and allowed Docker to run successfully.

1. Dockerではまった
吉田@板橋

2. というかそれ以前の話
Dockerの準備ではまった
2

3. 既存の環境でDockerを使う
• Debian Dockerで検索
– 公式ドキュメントがあった。
– https://docs.docker.com/installation/debian/
– Debian Jessie (Testing)は公式リポジトリにある
• # apt-get install docker.io
– Debian Wheezy(Stable)はbackport+web install
• http://http.debian.net/debian wheezy-backports
– Kernelのupdate(3.2->3.16)
• # curl -sSL https://get.docker.com/ | sh
3

4. 現状の環境
• Debian wheezy@Dell SC440
• 今ならJessieに上げてもいいか。
• JessieへのUpgrade実行
– Debian Wheezy から Jessie にディストリビューショ
ンアップグレードしてみる
• http://matoken.org/blog/blog/2013/05/29/debian-
wheezy2jessie/
– 後で見つけた公式:
• https://www.debian.org/releases/testing/i386/release-
notes/ch-upgrading.ja.html
• 結構時間はかかるが無事終了 4

5. dockerのパッケージインストール
# apt-get install docker.io
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
aufs-tools cgroupfs-mount git git-man libapparmor1 makedev mountall plymouth
Suggested packages:
btrfs-tools lxc rinse git-daemon-run git-daemon-sysvinit git-doc git-el git-email git-gui
gitk gitweb git-arch git-cvs git-mediawiki git-svn
plymouth-themes
The following NEW packages will be installed:
aufs-tools cgroupfs-mount docker.io git git-man libapparmor1 makedev mountall
plymouth
0 upgraded, 9 newly installed, 0 to remove and 0 not upgraded.
Need to get 3917 kB/8476 kB of archives.
After this operation, 42.3 MB of additional disk space will be used.
問題なし 5

6. dockerマシン実行
• # docker run -i -t ubuntu /bin/bash
• Unable to find image 'ubuntu' locally
• Pulling repository ubuntu
• 5ba9dab47459: Download complete
• 511136ea3c5a: Download complete
• 27d47432a69b: Download complete
• 5f92234dcf1e: Download complete
• 51a9c7c1f8bb: Download complete
• Status: Downloaded newer image for ubuntu:latest
• Error response from daemon: Cannot start container
67c78ec5687ed515ca6d165380e62c3050e17ef9d04dac58b0532b630c7ad
3f6: exec format error
問題発生 6

7. いろいろ調べてみた
• service docker stop/start
– etc...
• イメージ削除して再実行
– etc..
• がよく分からん。
7

8. 改めてドキュメントを見る
https://docs.docker.com/installation/debian/
• Debian Jessie 8.0 (64-bit)
• Debian Wheezy/Stable 7.x (64-bit)
...
$ uname -a
Linux sc440 3.16.0-4-686-pae #1 SMP Debian
3.16.7-ckt2-1 (2014-12-08) i686 GNU/Linux
$ uname -m
i686 8

9. 原因判明
• さて、64bit環境に移行するにはどうすればい
いか。
• https://wiki.debian.org/Migrate32To64Bit
9

10. Migrate32To64Bit
https://wiki.debian.org/Migrate32To64Bit
Migrate a 32-bit debian installation to 64-bit one (i386 to x86_64)
• Check wether your Intel/AMD processor supports the 64-bit "long mode"
• Install a 64-bit kernel
• Create a 64-bit mini system
• Create a list of the 64-bit binaries of the mini system
• Upgrade your 32-bit system closest to the mini system
• Boot your rescue disk
• Overwrite your 32-bit base system
• Reboot to your 64-bit system
• Reinstall all the packages
• Resinstall all remained 32-bit packages
以下250行ほど
大変面倒 10

11. KernelだけUpdate
• # apt-get install lib64z1 lib64ncurses5 linux-image-amd64
• Reading package lists... Done
• Building dependency tree
• Reading state information... Done
• The following extra packages will be installed:
• lib64tinfo5 libc6-amd64 linux-image-3.16.0-4-amd64
• Suggested packages:
• linux-doc-3.16 debian-kernel-handbook
• The following NEW packages will be installed:
• lib64ncurses5 lib64tinfo5 lib64z1 libc6-amd64 linux-image-3.16.0-4-amd64 linux-image-
amd64
• 0 upgraded, 6 newly installed, 0 to remove and 0 not upgraded.
• Need to get 36.6 MB of archives.
• After this operation, 173 MB of additional disk space will be used.
• (中略)
• Generating grub configuration file ...
• Found linux image: /boot/vmlinuz-3.16.0-4-686-pae
• Found initrd image: /boot/initrd.img-3.16.0-4-686-pae
• Found linux image: /boot/vmlinuz-3.16.0-4-amd64
• Found initrd image: /boot/initrd.img-3.16.0-4-amd64 11

12. grubで64bit版Kernelを選んでboot
• # uname -m
• x86_64
• # uname -a
• Linux sc440 3.16.0-4-amd64 #1 SMP Debian
3.16.7-ckt2-1 (2014-12-08) x86_64 GNU/Linux
12

13. それ以降は
• 面倒なので省略
• Kernelだけ64bit(x86_64)
• Userlandは32bit
# file /bin/ls
/bin/ls: ELF 32-bit LSB executable, Intel 80386,
version 1 (SYSV), dynamically linked (uses
shared libs), for GNU/Linux 2.6.32
13

14. 結果
• # docker run -i -t ubuntu /bin/bash
• root@7144e1a34412:/# cat /etc/lsb-release
• DISTRIB_ID=Ubuntu
• DISTRIB_RELEASE=14.04
• DISTRIB_CODENAME=trusty
• DISTRIB_DESCRIPTION="Ubuntu 14.04.1 LTS"
問題なし
以上14