Unfortunately, pkill doesn't distinguish between kernel and user space
processes, so we need to make sure we don't accidentally kill kernel
threads.
Normally, a kernel thread ignores all signals, but there are a few that
do. A quick grep on the kernel source tree (as of kernel 4.6.0) shows
the following source files which use allow_signal():
drivers/isdn/mISDN/l1oip_core.c
drivers/md/md.c
drivers/misc/mic/cosm/cosm_scif_server.c
drivers/misc/mic/cosm_client/cosm_scif_client.c
drivers/net/wireless/broadcom/brcm80211/brcmfmac/sdio.c
drivers/staging/rtl8188eu/core/rtw_cmd.c
drivers/staging/rtl8712/rtl8712_cmd.c
drivers/target/iscsi/iscsi_target.c
drivers/target/iscsi/iscsi_target_login.c
drivers/target/iscsi/iscsi_target_nego.c
drivers/usb/atm/usbatm.c
drivers/usb/gadget/function/f_mass_storage.c
fs/jffs2/background.c
fs/lockd/clntlock.c
fs/lockd/svc.c
fs/nfs/nfs4state.c
fs/nfsd/nfssvc.c
While not all of these are necessarily kthreads and some functionality
may still be unimpeded, it's still quite harmful and can cause
unexpected side-effects, especially because some of these kthreads are
storage-related (which we obviously don't want to kill during bootup).
During discussion at #15226, @dezgeg suggested the following
implementation:
for pid in $(pgrep -v -f '@'); do
if [ "$(cat /proc/$pid/cmdline)" != "" ]; then
kill -9 "$pid"
fi
done
This has a few downsides:
* User space processes which use an empty string in their command line
won't be killed.
* It results in errors during bootup because some shell-related
processes are already terminated (maybe it's pgrep itself, haven't
checked).
* The @ is searched within the full command line, not just at the
beginning of the string. Of course, we already had this until now, so
it's not a problem of his implementation.
I posted an alternative implementation which doesn't suffer from the
first point, but even that one wasn't sufficient:
for pid in $(pgrep -v -f '^@'); do
readlink "/proc/$pid/exe" &> /dev/null || continue
echo "$pid"
done | xargs kill -9
This one spawns a subshell, which would be included in the processes to
kill and actually kills itself during the process.
So what we have now is even checking whether the shell process itself is
in the list to kill and avoids killing it just to be sure.
Also, we don't spawn a subshell anymore and use /proc/$pid/exe to
distinguish between user space and kernel processes like in the comments
of the following StackOverflow answer:
http://stackoverflow.com/a/12231039
We don't need to take care of terminating processes, because what we
actually want IS to terminate the processes.
The only point where this (and any previous) approach falls short if we
have processes that act like fork bombs, because they might spawn
additional processes between the pgrep and the killing. We can only
address this with process/control groups and this still won't save us
because the root user can escape from that as well.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Fixes: #15226
A user noticed the example for `hosts`, took the `mode` permissions literally, and ended up with surprising behavior on their system. Updating the documentation to not reference a real config file which might have real permissions requirements.
Continuation of 79c3c16dcb. Systemd 229
sets the default RLIMIT_CORE to infinity, causing systems to be
littered with core dumps when systemd.coredump.enable is disabled.
This restores the 15.09 soft limit of 0 and hard limit of infinity.
This reverts commit 45c218f893.
Busybox's modprobe causes numerous "Unknown symbol" errors in the
kernel log, even though the modules do appear to load correctly.
Systemd 229 sets kernel.core_pattern to "|/bin/false" by default,
unless systemd-coredump is enabled. Revert back to the default of
writing "core" in the current directory.
Also add required systemd services for starting/stopping mdmon.
Closes#13447.
abbradar: fixed `mdadmShutdown` service name according to de facto conventions.
Since we don't restart sysinit.service in switch-to-configuration, this
additionally overrides systemd-binfmt.service to depend on
proc-sys-fs-binfmt_misc.automount, which is normally provided by
sysinit.service.
- Enforce that an option declaration has a "defaultText" if and only if the
type of the option derives from "package", "packageSet" or "nixpkgsConfig"
and if a "default" attribute is defined.
- Enforce that the value of the "example" attribute is wrapped with "literalExample"
if the type of the option derives from "package", "packageSet" or "nixpkgsConfig".
- Warn if a "defaultText" is defined in an option declaration if the type of
the option does not derive from "package", "packageSet" or "nixpkgsConfig".
- Warn if no "type" is defined in an option declaration.
This reverts commit b861bf8ddf, because according to @mdorman [1] this
change rendered his NixOS systems unbootable, and we probably don't want that.
[1] b861bf8ddf (commitcomment-16058598)
Allow usage of list of strings instead of a comma-separated string
for filesystem options. Deprecate the comma-separated string style
with a warning message; convert this to a hard error after 16.09.
15.09 was just released, so this provides a deprecation period during
the 16.03 release.
closes#10518
Signed-off-by: Robin Gloster <mail@glob.in>
It's not entirely clear why this happens, but sometimes /proc/1/exe
returns a bogus value, like
/ar3a3j6b9livhy5fcfv69izslhgk4gcz-systemd-217/lib/systemd/systemd. In
any case, we can just conservatively assume that we need to restart
systemd when this happens.
Fixes#10261.
