如何提供嵌套的overlayfs

Question

我尝试将覆盖层挂载为下一层覆盖层，但经过两层之后它就崩溃了

mount -t overlayfs -o rw,lowerdir=/tmp/test/layers/centos5.6-layer0-lower,upperdir=/tmp/test/layers/centos5.6-layer0-upper overlayfs /tmp/mount/centos5.6-layer0-mount
# remove deleted files into overlayfs
find /tmp/mount/centos5.6-layer0-mount -lname '(overlay-whiteout)' -exec rm -rf {} \;

mount -t overlayfs -o rw,lowerdir=/tmp/mount/centos5.6-layer0-mount,upperdir=/tmp/test/layers/centos5.6-layer1-upper overlayfs /tmp/mount/centos5.6-layer1-mount
# remove deleted files into overlayfs
find /tmp/mount/centos5.6-layer1-mount -lname '(overlay-whiteout)' -exec rm -rf {} \;

mount -t overlayfs -o rw,lowerdir=/tmp/mount/centos5.6-layer1-mount,upperdir=/tmp/test/layers/centos5.6-layer2-upper overlayfs /tmp/mount/centos5.6-layer2-mount
mount: wrong fs type, bad option, bad superblock on overlayfs,
       missing codepage or helper program, or other error
       (for several filesystems (e.g. nfs, cifs) you might
       need a /sbin/mount.<type> helper program)
       In some cases useful info is found in syslog - try
       dmesg | tail  or so
# remove deleted files into overlayfs
find /tmp/mount/centos5.6-layer2-mount -lname '(overlay-whiteout)' -exec rm -rf {} \;

mount -t overlayfs -o rw,lowerdir=/tmp/mount/centos5.6-layer2-mount,upperdir=/tmp/test/layers/centos5.6-layer3-upper overlayfs /tmp/mount/centos5.6-layer3-mount
find /tmp/mount/centos5.6-layer3-mount -lname '(overlay-whiteout)' -exec rm -rf {} \;

如何提供更多的2层以上？

Answer 1

如果您检查dmesg输出，您将看到内核声明试图超过最大堆叠深度：

overlayfs: maximum fs stacking depth exceeded

实际上，堆叠深度仅限于2，请参阅overlayfs开发分支：

• 水深
• 堆垛深度检查

如果您想超越这个深度，可以尝试更改常量并构建自己的内核。但是，请记住堆栈溢出的风险(根据注释)。