yahoo-eng-team team mailing list archive

[Scott Moser <smoser@xxxxxxxxxx>]

Public bug reported:

output of cloud-init-local.service can get lost in systemd.
The result is that there is no output in /var/log/cloud-init.log from cloud-init-local.service.

There is some information in https://code.launchpad.net/~harlowja/cloud-init/+git/cloud-init/+merge/301729
about how this occurrs and how it used to work.
copying part of that here:


Cloud-init's logging basically employed a "try syslog and fallback to direct log to file".
The proposed "just log to a file" is definitely dramatically simpler and advantageous in some cases.

The way the "try syslog and fallback" works (or worked) on Ubuntu up
until systemd was:

a.) cloud-init init --local
    1. read logging config,
    2. attempt to log to syslog ([ *log_base, *log_syslog ])
    3. that fail, so it log to file directly

b.) cloud-init init
   1.) rsyslog would have /dev/log up functional at this point
   2.) cloud-init logging config read and ends up logging to syslog

Systemd changed some things in teh way /dev/log was handled, and the
above no longer worked well.

Additionally, cloud-init installs a file
/etc/rsyslog.d/21-cloudinit.conf which tells rsyslog to redirect
messages generated by cloud-init to /var/log/cloud-init.log

The value of doing this in this way was that we use syslog, so if the
user had configured the system to log remotely, cloud-init's logs would
go to that remote system as they desired.

If we directly log to a file, then cloud-init's log messages will not
without further configuration go to syslog.

One other thing to be aware of is that cloud-init can itself configure
rsyslog through cloudinit/config/cc_rsyslog.py . So, the user could
provide in user-data some rsyslog configuration, and then the system's
syslog (including cloud-init messages) would start goign to that remote
server as soon as they realistically could.

** Affects: cloud-init
     Importance: Medium
         Status: Fix Committed

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https://bugs.launchpad.net/bugs/1643990

Title:
  cloud-init-local.service messages not written to /var/log/cloud-
  init.log in systemd

Status in cloud-init:
  Fix Committed

Bug description:
  output of cloud-init-local.service can get lost in systemd.
  The result is that there is no output in /var/log/cloud-init.log from cloud-init-local.service.

  There is some information in https://code.launchpad.net/~harlowja/cloud-init/+git/cloud-init/+merge/301729
  about how this occurrs and how it used to work.
  copying part of that here:

  
  Cloud-init's logging basically employed a "try syslog and fallback to direct log to file".
  The proposed "just log to a file" is definitely dramatically simpler and advantageous in some cases.

  The way the "try syslog and fallback" works (or worked) on Ubuntu up
  until systemd was:

  a.) cloud-init init --local
      1. read logging config,
      2. attempt to log to syslog ([ *log_base, *log_syslog ])
      3. that fail, so it log to file directly

  b.) cloud-init init
     1.) rsyslog would have /dev/log up functional at this point
     2.) cloud-init logging config read and ends up logging to syslog

  Systemd changed some things in teh way /dev/log was handled, and the
  above no longer worked well.

  Additionally, cloud-init installs a file
  /etc/rsyslog.d/21-cloudinit.conf which tells rsyslog to redirect
  messages generated by cloud-init to /var/log/cloud-init.log

  The value of doing this in this way was that we use syslog, so if the
  user had configured the system to log remotely, cloud-init's logs
  would go to that remote system as they desired.

  If we directly log to a file, then cloud-init's log messages will not
  without further configuration go to syslog.

  One other thing to be aware of is that cloud-init can itself configure
  rsyslog through cloudinit/config/cc_rsyslog.py . So, the user could
  provide in user-data some rsyslog configuration, and then the system's
  syslog (including cloud-init messages) would start goign to that
  remote server as soon as they realistically could.

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