leaking orphaned processes

01-upstart-normal.sh

root@u1404:~# cat /etc/init/orph.conf
description "orphaned process / process group test"
respawn
script
    sleep 9999 &
    sleep 4444
end script

root@u1404:~# start orph
orph start/running, process 3269

root@u1404:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 3269     1  3269  3269 ?           -1     0 /bin/sh -e /proc/self/fd/9
 3271  3269  3269  3269 ?           -1     0  \_ sleep 9999
 3272  3269  3269  3269 ?           -1     0  \_ sleep 4444

# All processes are in the same process group (3269). Let's trace their signals and stop the upstart job.

root@u1404:~# for p in $(pidof sleep); do strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /" & done
[1] 3282
[2] 3284
root@u1404:~# 3271: Process 3271 attached
3272: Process 3272 attached

# "stop orph" will terminate both sleep processes:

root@u1404:~# stop orph
3272: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
3271: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
3272: +++ killed by SIGTERM +++
3271: +++ killed by SIGTERM +++
orph stop/waiting
[1]-  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"
[2]+  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"

02-upstart-failure.sh

# If the main process gets killed or dies abnormally the background process gets adopted by init and "leaks":

root@u1404:~# start orph
orph start/running, process 3315

root@u1404:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 3315     1  3315  3315 ?           -1     0 /bin/sh -e /proc/self/fd/9
 3317  3315  3315  3315 ?           -1     0  \_ sleep 9999
 3318  3315  3315  3315 ?           -1     0  \_ sleep 4444

root@u1404:~# for p in $(pidof sleep); do strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /" & done
[1] 3443
[2] 3445
root@u1404:~# 3317: Process 3317 attached
3318: Process 3318 attached

root@u1404:~# kill 3318
3318: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1991, si_uid=0} ---
3318: +++ killed by SIGTERM +++
[1]-  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"

root@u1404:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 1314     1  1314  1314 tty1      1314     0 /sbin/getty -8 38400 tty1
 3317     1  3315  3315 ?           -1     0 sleep 9999
 3454     1  3454  3454 ?           -1     0 /bin/sh -e /proc/self/fd/9
 3456  3454  3454  3454 ?           -1     0  \_ sleep 9999
 3457  3454  3454  3454 ?           -1     0  \_ sleep 4444
Raw

03-systemd-normal.sh

root@u1604:~# cat /etc/systemd/system/orph.service 
[Unit]
Description=orphaned process / process group test
[Service]
Restart=on-failure
ExecStart=/bin/sh -ec 'sleep 9999 & sleep 4444'

root@u1604:~# systemctl start orph.service

root@u1604:~# systemctl status orph.service
* orph.service - orphaned process / process group test
   Loaded: loaded (/etc/systemd/system/orph.service; static; vendor preset: enabled)
   Active: active (running) since Sun 2016-05-15 19:29:27 UTC; 4s ago
 Main PID: 14847 (sh)
    Tasks: 3 (limit: 512)
   CGroup: /system.slice/orph.service
           |-14847 /bin/sh -ec sleep 9999 & sleep 4444
           |-14849 sleep 9999
           `-14850 sleep 4444
May 15 19:29:27 u1604 systemd[1]: Started orphaned process / process group test.

root@u1604:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 1398     1  1398  1398 ?           -1     0 /sbin/dhclient -1 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0
14847     1 14847 14847 ?           -1     0 /bin/sh -ec sleep 9999 & sleep 4444
14849 14847 14847 14847 ?           -1     0  \_ sleep 9999
14850 14847 14847 14847 ?           -1     0  \_ sleep 4444

root@u1604:~# for p in $(pidof sleep); do strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /" & done
[1] 14861
[2] 14863
root@u1604:~# 14850: strace: Process 14850 attached
14849: strace: Process 14849 attached

root@u1604:~# service orph stop
14850: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
14850: +++ killed by SIGTERM +++
14849: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
14849: +++ killed by SIGTERM +++
[1]-  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"
[2]+  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"

04-systemd-failure.sh

root@u1604:~# systemctl start orph.service

root@u1604:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 1398     1  1398  1398 ?           -1     0 /sbin/dhclient -1 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0
14895     1 14895 14895 ?           -1     0 /bin/sh -ec sleep 9999 & sleep 4444
14897 14895 14895 14895 ?           -1     0  \_ sleep 9999
14898 14895 14895 14895 ?           -1     0  \_ sleep 4444

root@u1604:~# for p in $(pidof sleep); do strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /" & done
[1] 14907
[2] 14909
root@u1604:~# 14898: strace: Process 14898 attached
14897: strace: Process 14897 attached

root@u1604:~# kill -9 14898
root@u1604:~# 14898: +++ killed by SIGKILL +++
14897: --- SIGTERM {si_signo=SIGTERM, si_code=SI_USER, si_pid=1, si_uid=0} ---
14897: +++ killed by SIGTERM +++
[1]-  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"
[2]+  Done                    strace -f -e trace=signal -p "$p" 2>&1 | sed -e "s/^/$p: /"

root@u1604:~# ps faxo pid,ppid,pgid,sid,tname,tpgid,uid,cmd | tee >(head -n1 >&2) | grep -v grep | grep -C1 sleep
  PID  PPID  PGID   SID TTY      TPGID   UID CMD
 1398     1  1398  1398 ?           -1     0 /sbin/dhclient -1 -v -pf /run/dhclient.eth0.pid -lf /var/lib/dhcp/dhclient.eth0.leases -I -df /var/lib/dhcp/dhclient6.eth0.leases eth0
14914     1 14914 14914 ?           -1     0 /bin/sh -ec sleep 9999 & sleep 4444
14916 14914 14914 14914 ?           -1     0  \_ sleep 9999
14917 14914 14914 14914 ?           -1     0  \_ sleep 4444

root@u1604:~# systemctl status orph.service
* orph.service - orphaned process / process group test
   Loaded: loaded (/etc/systemd/system/orph.service; static; vendor preset: enabled)
   Active: active (running) since Sun 2016-05-15 19:33:21 UTC; 1min 0s ago
 Main PID: 14914 (sh)
    Tasks: 3 (limit: 512)
   CGroup: /system.slice/orph.service
           |-14914 /bin/sh -ec sleep 9999 & sleep 4444
           |-14916 sleep 9999
           `-14917 sleep 4444
May 15 19:33:21 u1604 systemd[1]: Started orphaned process / process group test.