------- Comment From vcd...@us.ibm.com 2014-10-20 16:04 EDT------- (In reply to comment #8) > This is mandated by POSIX, see > http://pubs.opengroup.org/onlinepubs/9699919799/utilities/crontab.html
Further research explores the problem with shell link: root@ucrypt:/# ls -l /bin/sh lrwxrwxrwx 1 root root 4 Sep 16 10:54 /bin/sh -> dash In other words, it is dash (a slim shell to provide faster boot times) that can not execute a binary command to override itself. You may see the different behaviors of dash vs bash: root@ucrypt:/# /bin/dash -c cat ... ... root@ucrypt:~# ps -ef | grep cat # at another terminal root 6611 6462 0 15:45 pts/0 00:00:00 /bin/dash -c cat root 6612 6611 0 15:45 pts/0 00:00:00 cat root@ucrypt:/# /bin/bash -c cat ... ... root@ucrypt:/# ps -ef | grep cat # at another terminal root 6615 6462 0 15:47 pts/0 00:00:00 cat -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to cron in Ubuntu. https://bugs.launchpad.net/bugs/1337576 Title: dash inability - cron start binary with /bin/sh Status in “cron” package in Ubuntu: New Bug description: -- Problem Description -- CRON uses shell to start a binary executable defined in crontab, which is a waste of the resources for the extra shell process hanging in the system. It's supposed to run it directly with exec system call. *** Here are some command outputs to see the extra process(12327) and relevant information: *** # ps -ef | grep -e CRON -e PMLnx root 12326 771 0 13:59 ? 00:00:00 CRON root 12327 12326 0 13:59 ? 00:00:00 /bin/sh -c /var/perf/pm/bin/daemon_PMLnx <--- extra layer, a waste root 12328 12327 0 13:59 ? 00:00:00 /var/perf/pm/bin/daemon_PMLnx # crontab -l 59 * * * * /var/perf/pm/bin/daemon_PMLnx # file /var/perf/pm/bin/daemon_PMLnx /var/perf/pm/bin/daemon_PMLnx: ELF 64-bit LSB executable, 64-bit PowerPC or cisco 7500, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 3.0.0, BuildID[sha1]=1761d6d97eabb4e52870cb517fe6bf457e5bf89e, stripped # uname -a Linux ubuntu 3.13.0-24-generic #46-Ubuntu SMP Thu Apr 10 19:09:21 UTC 2014 ppc64le ppc64le ppc64le GNU/Linux # dpkg -l cron Name Version Architecture Description +++-=====-==================-=============-========================= ii cron 3.0pl1-124ubuntu2 ppc64el process scheduling daemon *** Expect cron to directly execute a binary like this *** # ps -ef | grep -e CRON -e PMLnx root 2293 2223 0 09:59 ? 00:00:00 /usr/sbin/CRON -n root 2294 2293 0 09:59 ? 00:00:00 /var/perf/pm/bin/daemon_PMLnx # uname -a Linux hulala 3.12.15-3-default #1 SMP Wed Apr 2 17:08:55 UTC 2014 (69c2ea8) ppc64le ppc64le ppc64le GNU/Linux # cat /etc/SuSE-release SUSE Linux Enterprise Server 12 (ppc64le) VERSION = 12 PATCHLEVEL = 0 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cron/+bug/1337576/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
