2

On an Amazon Linux (RHEL + CentOS fusion) OS server (this is actually an EC2 instance within a EMR cluster 4.5.0 AMI if that helps), we can see –

$ ls /etc/init.d/
acpid                        cloud-init-local             instance-controller          ntpd
…..

$ ls /etc/init/
control-alt-delete.conf              hadoop-yarn-resourcemanager.conf       hive-metastore.conf              
…..

Further we can also see the following –

$ sudo stat /proc/1/exe
  File: ‘/proc/1/exe’ -> ‘/sbin/init’

$ /sbin/init --version
init (upstart 0.6.5)    

which tells us that the Amazon Linux based EC2 hosts are using upstart init system during boot process.[1]

Based on this, my understanding is that –

  1. Different daemons or services on this host are using either upstart or systemd.
  2. systemd and upstart init systems coexist together and both of them are active at any given time. Is this possible? Is this understanding correct (including the verbiage)?

If yes, can you please let me know how can we achieve this (I do not see any ‘systemd’ named script on any of the EC2 hosts)?

Note : I think this might be a classic repeated question, but I am a little confused with multiple articles with inconclusive answers.

Ref – [1] https://forums.aws.amazon.com/message.jspa?messageID=731256 (“Systemd is not a one-to-one drop-in replacement.“)

4

Different daemons or services on this host are using either upstart or systemd.

I suspect your system is using upstart exclusively. What makes you think systemd is involved?

systemd and upstart init systems coexist together and both of them are active at any given time. Is this possible? Is this understanding correct (including the verbiage)?

Different init systems do not coexist, and you would certainly not have more than one active at any time. They can coexist only in the limited sense that configurations might exist for both, but only one is in use at any given time.

  • 1
    In case anyone says "But Ubuntu 15 ...!": Ubuntu 15 runs systemd and upstart side by side, but only inasmuch as systemd is the system-wide service manager and upstart is the per-session service manager(s). askubuntu.com/questions/778785 askubuntu.com/questions/613366 – JdeBP Nov 25 '16 at 8:46
  • 3
    The presence of init.d does not mean systemd. The init.d scripts are SysV style which upstart and systemd are both backwards compatible. – ChristopherB Nov 27 '16 at 16:16

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