Quoting Stéphane Graber (stgra...@ubuntu.com):
> From: Serge Hallyn <serge.hal...@ubuntu.com>
>
> Note we still need the function to detect a MS_SHARED /, bc
> if we detect that then we need to umount the chroot tmpfs
> mount which lxc-start created, whose mount was forwarded to
> the host mounts namespace.
Wait I'm confused - I thought this wasn't working for you and you
weren't using it / didn't need it?
For those playing along at home: in a previous patch I detected /
being MS_SHARED, in which case I created a MS_PRIVATE tmpfs chroot
just to pivot_root out of. (technically, the parent of the chroot
needs to be private, hence the tmpfs under which we are chrooted into
/root). This patch moves the creation of a MS_PRIVATE chroot to
much later in the container startup. It does it anytime pivot_root
fails with -EINVAL, because there are other possible causes of that.
In particular, if you are on a system where / is MS_NOUSER.
> Signed-off-by: Serge Hallyn <serge.hal...@ubuntu.com>
> Acked-by: Stéphane Graber <stgra...@ubuntu.com>
> ---
> src/lxc/conf.c | 31 ++++++++++++++++++++-----------
> 1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/src/lxc/conf.c b/src/lxc/conf.c
> index 945c3b8..09cfa9f 100644
> --- a/src/lxc/conf.c
> +++ b/src/lxc/conf.c
> @@ -1163,13 +1163,6 @@ static int setup_rootfs(struct lxc_conf *conf)
> return -1;
> }
>
> - if (detect_shared_rootfs()) {
> - if (chroot_into_slave(conf)) {
> - ERROR("Failed to chroot into slave /");
> - return -1;
> - }
> - }
> -
> if (mount_rootfs(rootfs->path, rootfs->mount)) {
> ERROR("failed to mount rootfs");
> return -1;
> @@ -1180,17 +1173,33 @@ static int setup_rootfs(struct lxc_conf *conf)
> return 0;
> }
>
> -int setup_pivot_root(const struct lxc_rootfs *rootfs)
> +static int setup_pivot_root(struct lxc_conf *conf)
> {
> + const struct lxc_rootfs *rootfs = &conf->rootfs;
> +
> if (!rootfs->path)
> return 0;
>
> - if (setup_rootfs_pivot_root(rootfs->mount, rootfs->pivot)) {
> + if (setup_rootfs_pivot_root(rootfs->mount, rootfs->pivot) == 0)
> + return 0;
> +
> + if (errno != EINVAL) {
> ERROR("failed to setup pivot root");
> return -1;
> }
>
> - return 0;
> + INFO("pivot_root failed. Trying pivot_root under custom chroot.");
> +
> + if (chroot_into_slave(conf)) {
> + ERROR("Failed to chroot into slave /");
> + return -1;
> + }
> +
> + if (setup_rootfs_pivot_root(rootfs->mount, rootfs->pivot) == 0)
> + return 0;
> +
> + ERROR("failed to setup pivot root");
> + return -1;
> }
>
> static int setup_pts(int pts)
> @@ -2649,7 +2658,7 @@ int lxc_setup(const char *name, struct lxc_conf
> *lxc_conf)
> }
> #endif
>
> - if (setup_pivot_root(&lxc_conf->rootfs)) {
> + if (setup_pivot_root(lxc_conf)) {
> ERROR("failed to set rootfs for '%s'", name);
> return -1;
> }
> --
> 1.8.0
>
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