I came across this SO post:
"You have killed the process, but a dead process doesn't disappear from the process table until its parent process performs a task called "reaping" (essentially calling wait(3) for that process to read its exit status). Dead processes that haven't been reaped are called "zombie processes."
Here is my defunct process:
ps aux | grep ruby 1000 11958 16.3 0.0 0 0 pts/3 Z Jul11 1065:28 [ruby] <defunct>
This is what it was supposed to do:
RAILS_ENV=production bundle exec ruby lib/daemons/db_service_ctl start%
Basically it runs the Rails daemons process. I wanted to restart it so I tried to kill it but it refused to die, and now I have a defunct process.
Here is its parent process:
ps -f 11958 UID PID PPID C STIME TTY STAT TIME CMD 1000 11958 11957 16 Jul11 pts/3 Z 1065:28 [ruby] <defunct>
The parent process is 11957. The proc cmdline looks like this:
/proc/11957 $ cat cmdline /bin/sh./script/db_service.sh%
That looks like the same shell script that I executed as the daemons process!
So how can this be the parent process too?