From 66e411811b8090d1bfd6620fc84472d83f723fa1 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Fri, 15 Mar 2013 16:41:40 +0100 Subject: sd-booted: update sd_booted() check a bit Previously we were testing whether /sys/fs/cgroup/systemd/ was a mount point. This might be problematic however, when the cgroup trees are bind mounted into a container from the host (which should be absolutely valid), which might create the impression that the container was running systemd, but only the host actually is. Replace this by a check for the existance of the directory /run/systemd/system/, which should work unconditionally, since /run can never be a bind mount but *must* be a tmpfs on systemd systems, which is flushed at boots. This means that data in /run always reflects information about the current boot, and only of the local container, which makes it the perfect choice for a check like this. (As side effect this is nice to Ubuntu people who now use logind with the systemd cgroup hierarchy, where the old sd_booted() check misdetects systemd, even though they still run legacy Upstart.) --- man/sd_booted.xml | 9 ++++----- src/core/mount-setup.c | 6 +++++- src/libsystemd-daemon/sd-daemon.c | 15 ++++++--------- 3 files changed, 15 insertions(+), 15 deletions(-) diff --git a/man/sd_booted.xml b/man/sd_booted.xml index 34f2cbfbc..ce5a34dc8 100644 --- a/man/sd_booted.xml +++ b/man/sd_booted.xml @@ -85,11 +85,10 @@ implementation. Internally, this function checks whether the - /sys/fs/cgroup/systemd virtual file - system is mounted, by comparing the st_dev value of - the stat() data of - /sys/fs/cgroup and - /sys/fs/cgroup/systemd. + directory /run/systemd/system/ + exists. A simple check like this can also be + implemented trivially in shell or any other + language. For details about the algorithm check the liberally licensed reference implementation sources: diff --git a/src/core/mount-setup.c b/src/core/mount-setup.c index 42cdc6dc5..ce10be944 100644 --- a/src/core/mount-setup.c +++ b/src/core/mount-setup.c @@ -440,7 +440,11 @@ int mount_setup(bool loaded_policy) { if (mount(NULL, "/", NULL, MS_REC|MS_SHARED, NULL) < 0) log_warning("Failed to set up the root directory for shared mount propagation: %m"); - /* Create a few directories we always want around */ + /* Create a few directories we always want around, Note that + * sd_booted() checks for /run/systemd/system, so this mkdir + * really needs to stay for good, otherwise software that + * copied sd-daemon.c into their sources will misdetect + * systemd. */ mkdir_label("/run/systemd", 0755); mkdir_label("/run/systemd/system", 0755); diff --git a/src/libsystemd-daemon/sd-daemon.c b/src/libsystemd-daemon/sd-daemon.c index 5b92e2e3d..79d8ca370 100644 --- a/src/libsystemd-daemon/sd-daemon.c +++ b/src/libsystemd-daemon/sd-daemon.c @@ -519,18 +519,15 @@ _sd_export_ int sd_booted(void) { #if defined(DISABLE_SYSTEMD) || !defined(__linux__) return 0; #else + struct stat st; - struct stat a, b; + /* We test whether the runtime unit file directory has been + * created. This takes place in mount-setup.c, so is + * guaranteed to happen very early during boot. */ - /* We simply test whether the systemd cgroup hierarchy is - * mounted */ - - if (lstat("/sys/fs/cgroup", &a) < 0) - return 0; - - if (lstat("/sys/fs/cgroup/systemd", &b) < 0) + if (lstat("/run/systemd/system/", &st) < 0) return 0; - return a.st_dev != b.st_dev; + return !!S_ISDIR(st.st_mode); #endif } -- cgit v1.2.3