Table of Contents

System File Examples

Table of Contents

Editing password or group files

To change the password of a system, we need to edit a file. A file is a complex object – once open there is a new world of possible promises to make about its contents. CFEngine has bundles of promises that are specially for editing.

body common control
{
      inputs => { "$(sys.libdir)/stdlib.cf" };
      bundlesequence => { "edit_passwd" };
}
bundle agent edit_passwd
{
  vars:
      "userset" slist => { "user1", "user2", "user3" };

  files:
      "/etc/passwd"
      edit_line => set_user_field("mark","7","/set/this/shell");

      "/etc/group"
      edit_line => append_user_field("root","4","@(main.userset)");
}

Editing password or group files custom

In this example the bundles from the Community Open Promise-Body Library are included directly in the policy instead of being input as a separate file.

body common control
{
      bundlesequence => { "addpasswd" };
}

bundle agent addpasswd
{
  vars:

      # want to set these values by the names of their array keys

      "pwd[mark]" string => "mark:x:1000:100:Mark Burgess:/home/mark:/bin/bash";
      "pwd[fred]" string => "fred:x:1001:100:Right Said:/home/fred:/bin/bash";
      "pwd[jane]" string => "jane:x:1002:100:Jane Doe:/home/jane:/bin/bash";

  files:

      "/tmp/passwd"
      create => "true",
      edit_line => append_users_starting("addpasswd.pwd");

}


bundle edit_line append_users_starting(v)
{
  vars:
      "index"        slist => getindices("$(v)");

  classes:
      "add_$(index)" not => userexists("$(index)");

  insert_lines:
      "$($(v)[$(index)])",
      ifvarclass => "add_$(index)";
}

bundle edit_line append_groups_starting(v)
{
  vars:
      "index"        slist => getindices("$(v)");

  classes:
      "add_$(index)" not => groupexists("$(index)");

  insert_lines:
      "$($(v)[$(index)])",
      ifvarclass => "add_$(index)";
}

Log rotation

body common control
{
      bundlesequence  => { "testbundle" };
}


bundle agent testbundle

{
  files:
      "/home/mark/tmp/rotateme"
      rename => rotate("4");
}


body rename rotate(level)
{
      rotate => "$(level)";
}

Garbage collection

body common control
{
      bundlesequence => { "garbage_collection" };
      inputs => { "cfengine_stdlib.cf" };
}


bundle agent garbage_collection
{
  files:

    Sunday::

      "$(sys.workdir)/nova_repair.log"

      comment => "Rotate the promises repaired logs each week",
      rename => rotate("7"),
      action => if_elapsed("10000");

      "$(sys.workdir)/nova_notkept.log"

      comment => "Rotate the promises not kept logs each week",
      rename => rotate("7"),
      action => if_elapsed("10000");

      "$(sys.workdir)/promise.log"

      comment => "Rotate the promises not kept logs each week",
      rename => rotate("7"),
      action => if_elapsed("10000");

    any::

      "$(sys.workdir)/outputs"

      comment => "Garbage collection of any output files",
      delete => tidy,
      file_select => days_old("3"),
      depth_search => recurse("inf");

      "$(sys.workdir)/"

      comment => "Garbage collection of any output files",
      delete => tidy,
      file_select => days_old("14"),
      depth_search => recurse("inf");

      # Other resources


      "/tmp"

      comment => "Garbage collection of any temporary files",
      delete => tidy,
      file_select => days_old("3"),
      depth_search => recurse("inf");

      "/var/log/apache2/.*bz"

      comment => "Garbage collection of rotated log files",
      delete => tidy,
      file_select => days_old("30"),
      depth_search => recurse("inf");

      "/var/log/apache2/.*gz"

      comment => "Garbage collection of rotated log files",
      delete => tidy,
      file_select => days_old("30"),
      depth_search => recurse("inf");

      "/var/log/zypper.log"

      comment => "Prevent the zypper log from choking the disk",
      rename => rotate("0"),
      action => if_elapsed("10000");

}

Manage a system file

Simple template
Simple versioned template
Macro template
Custom editing

Simple template

bundle agent hand_edited_config_file
{
  vars:
      "file_template" string =>
      "

127.0.0.1       localhost
::1             localhost ipv6-localhost ipv6-loopback
fe00::0         ipv6-localnet
ff00::0         ipv6-mcastprefix
ff02::1         ipv6-allnodes
ff02::2         ipv6-allrouters
ff02::3         ipv6-allhosts
10.0.0.100      host1.domain.tld host1
10.0.0.101      host2.domain.tld host2
10.0.0.20       host3.domain.tld host3
10.0.0.21       host4.domain.tld host4
";
      ##############################################################

  files:
      "/etc/hosts"
      comment => "Define the content of all host files from this master source",
      create => "true",
      edit_line => append_if_no_lines("$(file_template)"),
      edit_defaults => empty,
      perms => mo("$(mode)","root"),
      action => if_elapsed("60");
}

Simple versioned template

The simplest approach to managing a file is to maintain a master copy by hand, keeping it in a version controlled repository (e.g. svn), and installing this version on the end machine.

We'll assume that you have a version control repository that is located on some independent server, and has been checked out manually once (with authentication) in /mysite/masterfiles.

bundle agent hand_edited_config_file
{
  vars:

      "masterfiles"   string => "/mysite/masterfiles";
      "policy_server" string => "policy_host.domain.tld";

  files:

      "/etc/hosts"
      comment => "Synchronize hosts with a hand-edited template in svn",
      perms => m("644"),
      copy_from => remote_cp("$(masterfiles)/trunk/hosts_master","$(policy_server)");

  commands:

      "/usr/bin/svn update"
      comment => "Update the company document repository including manuals to a local copy",
      contain => silent_in_dir("$(masterfiles)/trunk"),
      ifvarclass => canonify("$(policy_server)");
}

Macro template

The next simplest approach to file management is to add variables to the template that will be expanded into local values at the end system, e.g. using variables like ‘$(sys.host)’ for the name of the host within the body of the versioned template.

bundle agent hand_edited_template
{
  vars:

      "masterfiles"   string => "/mysite/masterfiles";
      "policy_server" string => "policy_host.domain.tld";

  files:

      "/etc/hosts"

      comment => "Synchronize hosts with a hand-edited template in svn",
      perms => m("644"),
      create => "true",
      edit_line => expand_template("$(masterfiles)/trunk/hosts_master"),
      edit_defaults => empty,
      action => if_elapsed("60");

  commands:

      "/usr/bin/svn update"

      comment => "Update the company document repository including manuals to a local copy",
      contain => silent_in_dir("$(masterfiles)/trunk"),
      ifvarclass => canonify("$(policy_server)");

}

The macro template file may contain variables, as below, that get expanded by CFEngine.

bundle agent hand_edited_template
{
  vars:

      "masterfiles"   string => "/mysite/masterfiles";
      "policy_server" string => "policy_host.domain.tld";

  files:

      "/etc/hosts"

      comment => "Synchronize hosts with a hand-edited template in svn",
      perms => m("644"),
      create => "true",
      edit_line => expand_template("$(masterfiles)/trunk/hosts_master"),
      edit_defaults => empty,
      action => if_elapsed("60");

  commands:


      "/usr/bin/svn update"

      comment => "Update the company document repository including manuals to a local copy",
      contain => silent_in_dir("$(masterfiles)/trunk"),
      ifvarclass => canonify("$(policy_server)");

}

127.0.0.1 localhost $(sys.host) ::1 localhost ipv6-localhost ipv6-loopback fe00::0 ipv6-localnet ff00::0 ipv6-mcastprefix ff02::1 ipv6-allnodes ff02::2 ipv6-allrouters ff02::3 ipv6-allhosts 10.0.0.100 host1.domain.tld host1 10.0.0.101 host2.domain.tld host2 10.0.0.20 host3.domain.tld host3 10.0.0.21 host4.domain.tld host4

$(definitions.more_hosts) ```

Custom editing

If you do not control the starting state of the file, because it is distributed by an operating system vendor for instance, then editing the final state is the best approach. That way, you will get changes that are made by the vendor, and will ensure your own modifications are kept even when updates arrive.

bundle agent modifying_managed_file
{
  vars:

      "data"   slist => { "10.1.2.3 sirius", "10.1.2.4 ursa-minor", "10.1.2.5 orion"};

  files:

      "/etc/hosts"

      comment => "Append a list of lines to the end of a file if they don't exist",
      perms => m("644"),
      create => "true",
      edit_line => append_if_no_lines("modifying_managed_file.data"),
      action => if_elapsed("60");
}

Another example shows how to set the values of variables using a data-driven approach and methods from the standard library.

body common control
{
      bundlesequence  => { "testsetvar" };
}

bundle agent testsetvar
{
  vars:
      "v[variable_1]" string => "value_1";
      "v[variable_2]" string => "value_2";

  files:
      "/tmp/test_setvar"
      edit_line => set_variable_values("testsetvar.v");
}