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[hoyho]

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Hoyho's Blog,to record my coding life;D day

[ql20060101]

博主，我在Ubuntu 18.04.3 LTS上运行的时候遇到Error running pivot_root - invalid argument。 直接在shell上模拟：

# mount --bind /tmp/ns-pro/rootfs /tmp/ns-pro/rootfs

# pivot_root /tmp/ns-pro/rootfs /tmp/ns-pro/rootfs/.oldfs

报错： pivot_root: failed to change root from /tmp/ns-pro/rootfs' to/tmp/ns-pro/rootfs/.oldfs': Invalid argument 根据https://bugzilla.redhat.com/show_bug.cgi?id=1361043， 我尝试在pivot_root前执行“unshare -m”，然后才pass。

代码中是否也应该先进入新的namespace，然后syscall.PivotRoot？

[hoyho]

@ql20060101 博主，我在Ubuntu 18.04.3 LTS上运行的时候遇到Error running pivot_root - invalid argument。 直接在shell上模拟：

# mount --bind /tmp/ns-pro/rootfs /tmp/ns-pro/rootfs

# pivot_root /tmp/ns-pro/rootfs /tmp/ns-pro/rootfs/.oldfs

报错： pivot_root: failed to change root from /tmp/ns-pro/rootfs' to/tmp/ns-pro/rootfs/.oldfs': Invalid argument 根据https://bugzilla.redhat.com/show_bug.cgi?id=1361043， 我尝试在pivot_root前执行“unshare -m”，然后才pass。

代码中是否也应该先进入新的namespace，然后syscall.PivotRoot？

redhat的链接也提到了Yes, due to migration to systemd we use "shared" as the default propagation for mount points.

这里用shell执行mount --bind /tmp/ns-pro/rootfs /tmp/ns-pro/rootfs与demo是有点出入， https://gitee.com/hoyho/ns-proc/blob/mount-5/container-fs.go#L28 这里其实用到了syscall.MS_BIND|syscall.MS_REC,

// BIND remounts a subtree somewhere else.
BIND = unix.MS_BIND

// RBIND remounts a subtree and all possible submounts somewhere else.
RBIND = unix.MS_BIND | unix.MS_REC

   MS_REC (since Linux 2.4.11)
         Used in conjunction with MS_BIND to create a recursive bind
         mount, and in conjunction with the propagation type flags to
         recursively change the propagation type of all of the mounts
         in a subtree.  See below for further details.

这里通过指定mountflag 来改变了default propagation

根据文档描述http://man7.org/linux/man-pages/man8/mount.8.html：

The following commands allow one to recursively change the type of
  all the mounts under a given mountpoint.

        mount --make-rshared mountpoint
         mount --make-rslave mountpoint
         mount --make-rprivate mountpoint
         mount --make-runbindable mountpoint

所以我觉得可以把mount --bind 改为代码里的挂载参数（仅看文档猜测，未经实践🤪)