Hi, Emily. I propose this solution: in very beginning of your initramfs's init do equivalent of this: mkdir root mount --bind / root cd root mount --move . / chroot . And then everything else. This will create second mount of initramfs. Everything will look same, but pivot_root will work. Also, you can do this: create file named, say, "preinit" and put it to initramfs. Write to this file code above and put to the end of the file "exec /init". Of course, "preinit" could be written in shell or C or any other language. Add "rdinit=/preinit" to kernel command line. This will execute preinit at first, preinit will duplicate initramfs mount and then execute actual initramfs's init. I didn't test this, but I'm nearly sure it will work. If you want, I can test this. Also you can put "rdinit=/preinit" to CONFIG_CMDLINE. As well as I understand, CONFIG_CMDLINE will be merged with command line provided by bootloader, but I'm not sure. Also you can link small initramfs with /preinit to kernel image. Again, as well as I understand it will be merged with initramfs provided by bootloader. Thus, kernel with CONFIG_CMDLINE and with linked in initramfs with /preinit will behave very similarly to kernel with your patch. Of course, initial mount will not be empty, but I think this is a minor point. Of course, instead of that "mount --bind" trick you can do the same with "cp + rm" solution. Also, I remember I saw patch similar to yours in Linux mailing lists. It was rejected, too. If you want I can try to find it. I suggest solution described above. But let me also provide some alternative solutions. You can implement patch similar to yours, but which will work unconditionally, always. This will solve the problem once and for all. Ideally initial mount will be nullfs as suggested by Rob. I. e. file system, which has no state at all. To make sure containers cannot exchange data. I think such filesystem is easy to create. All operations will be no-ops. Look at "fs" directory in kernel tree and write something similar. Another way is to make pivot_root work with initial mount. I think this will be hard. Note that Rob Landley is absent from MAINTAINERS file ( https://elixir.bootlin.com/linux/latest/source/MAINTAINERS ), so he doesn't decide whether a patch will be accepted. (I doesn't decide, too. I'm not a kernel developer, I just occasionally found this thread and decided to answer.) If you ever want to start new discussion or sent new patch, then, please, sent it to LKML, not to initramfs@xxxxxxxxxxxxxxx . As you can see here: https://lore.kernel.org/initramfs/ , new discussions are started nearly once a month at initramfs@xxxxxxxxxxxxxxx , so I think very few people will see your message. Ask me any questions. -- Askar Safin
