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Without this patch, it is not possible to allocate PTYs when a generated rootfs image with a recent glibc and systemd is launched as a container on an RHEL7 system via machinectl/systemd-nspawn. The container boots, but `machinectl login mycontainer` fails. The culprit is /dev/pts/ptmx with 0000 perms. On a typical system, there are two `ptmx` devices. One is provided by the devpts at /dev/pts/ptmx and it is typically not directly accessed from userspace. The other one which actually *is* opened by processes is /dev/ptmx. Kernel's documentation says these days that /dev/ptmx should be either a symlink, or a bind mount of the /dev/pts/ptmx from devpts. When a container is launched via machinectl/machined/systemd-nspawn, the container manager prepares a root filesystem so that the container can live in an appropriate namespace (this is similar to what initramfs is doing on x86 desktops). During these preparations, systemd-nspawn mounts a devpts instance using a correct ptmxmode=0666 within the container-to-be's /dev/pts, and it adds a compatibility symlink at /dev/ptmx. However, once systemd takes over as an init in the container, /lib/systemd/systemd-remount-fs applies mount options from /etc/fstab to all fileystems. Because the buildroot's template used to not include the ptmxmode=... option, a default value of 0000 was taking an effect which in turn led to not being able to allocate any pseudo-terminals. The relevant kernel option was introduced upstream in commit 1f8f1e29 back in 2009. The oldest linux-headers referenced from buildroot's config is 3.0, and that version definitely has that commit. Mount options that are not understood by the system are anyway ignored, so backward compatibility is preserved. Signed-off-by: Jan Kundrát <jan.kundrat@cesnet.cz> Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be> [Thomas: fix commit title, adjust commit log.] Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> |
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| board | ||
| boot | ||
| configs | ||
| docs | ||
| fs | ||
| linux | ||
| package | ||
| support | ||
| system | ||
| toolchain | ||
| .defconfig | ||
| .gitignore | ||
| .gitlab-ci.yml | ||
| .gitlab-ci.yml.in | ||
| CHANGES | ||
| Config.in | ||
| Config.in.legacy | ||
| COPYING | ||
| DEVELOPERS | ||
| Makefile | ||
| Makefile.legacy | ||
| README | ||
Buildroot is a simple, efficient and easy-to-use tool to generate embedded Linux systems through cross-compilation. The documentation can be found in docs/manual. You can generate a text document with 'make manual-text' and read output/docs/manual/manual.text. Online documentation can be found at http://buildroot.org/docs.html To build and use the buildroot stuff, do the following: 1) run 'make menuconfig' 2) select the target architecture and the packages you wish to compile 3) run 'make' 4) wait while it compiles 5) find the kernel, bootloader, root filesystem, etc. in output/images You do not need to be root to build or run buildroot. Have fun! Buildroot comes with a basic configuration for a number of boards. Run 'make list-defconfigs' to view the list of provided configurations. Please feed suggestions, bug reports, insults, and bribes back to the buildroot mailing list: buildroot@buildroot.org You can also find us on #buildroot on Freenode IRC. If you would like to contribute patches, please read https://buildroot.org/manual.html#submitting-patches