binfmt_misc docker 下 ubuntu 18.04 中的问题

Question

正在尝试在 docker 容器中的 ubuntu:18.04 下获得交叉 chroot 运行。

在尝试安装 binfmt-support（qemu-user-static 的依赖项）时发生这种情况：

~ docker run -it ubuntu:18.04 /bin/bash
root@df5a34a47fe2:/# cd
root@df5a34a47fe2:~# apt-get update
...
root@df5a34a47fe2:~# apt-get install qemu-user-static
...
Setting up qemu-user-static (1:2.11+dfsg-1ubuntu7.9) ...
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
mount: /proc/sys/fs/binfmt_misc: permission denied.
update-binfmts: warning: Couldn't mount the binfmt_misc filesystem on /proc/sys/fs/binfmt_misc.
Setting up binfmt-support (2.1.8-2) ...
invoke-rc.d: could not determine current runlevel
invoke-rc.d: policy-rc.d denied execution of start.
root@df5a34a47fe2:~# echo $?
0

有谁知道这里发生了什么，是否相关以及如何解决？

Answer 1

binfmt 正在尝试将 qemu 注册为二进制加载程序，因此您无需每次需要运行二进制文件时都调用 qemu。为此，它需要容器没有的权限。

忽略这些警告，因为在构建映像时在主机上注册 binfmt 没有意义。

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