Using a Chef Recipe to Append Multiple Lines to a Config File

Using a Chef recipe to append multiple lines to a config file

As you said yourself, the recommended Chef pattern is to manage the whole file.

If you're using Chef 11 you could probably make use of partials for what you're trying to achieve.

There's more info here and on this example cookbook.

As long as you have access to the original config template, just append <%= render "original_config.erb" %> to the top of your parms_to_append.conf template.

Use a Chef recipe to modify a single line in a config file

I never figured out how to modify a single line in a config file using Chef, but here's the recipe I ended up using to disable THP settings for MongoDB.

Recipe: Install MongoDB

# Install MongoDB on Amazon Linux
# http://docs.mongodb.org/manual/tutorial/install-mongodb-on-amazon/

# 1: configure the package management system (yum)

# 2: install mongodb

# 3: configure mongodb settings

# 3.A: give mongod permission to files
# data & log directories (everything in /srv/mongodb)
# http://stackoverflow.com/questions/7948789/mongodb-mongod-complains-that-there-is-no-data-db-folder
execute "mongod_permission" do
    command "sudo chown -R mongod:mongod /srv/mongodb"
    #command "sudo chown mongod:mongod /var/run/mongodb/mongod.pid"
    #command "sudo chown -R $USER /srv/mongodb"
end

# 3.B: edit Transparent Huge Pages (THP) Settings
# get rid of mongod startup warning
# http://docs.mongodb.org/manual/reference/transparent-huge-pages/#transparent-huge-pages-thp-settings

# 3.B.1: disable
execute "disable_thp_khugepaged_defrag" do
    command "echo 0 | sudo tee /sys/kernel/mm/transparent_hugepage/khugepaged/defrag" # different b/c file doesn't have options list
end
execute "disable_thp_hugepage_defrag" do
    command "echo 'never > /sys/kernel/mm/transparent_hugepage/defrag' | sudo tee --append /sys/kernel/mm/transparent_hugepage/defrag"
end
execute "disable_thp_hugepage_enables" do
    command "echo 'never > /sys/kernel/mm/transparent_hugepage/enabled' | sudo tee --append /sys/kernel/mm/transparent_hugepage/enabled"
end

# 3.B.2: verify disabled on reboot
template "/etc/rc.local" do
    source "init-rc.local.erb"
    owner 'root'
    group 'root'
    mode '0775'
end

# 4: use upstart & monit to keep mongod alive

Template: init-rc.local.erb

touch /var/lock/subsys/local

if test -f /sys/kernel/mm/transparent_hugepage/khugepaged/defrag; then
  echo 0 > /sys/kernel/mm/transparent_hugepage/khugepaged/defrag
fi
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
  echo never > /sys/kernel/mm/transparent_hugepage/defrag
fi
if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
  echo never > /sys/kernel/mm/transparent_hugepage/enabled
fi

How can I create a simple text file that contains more than one line of text with CHEF?

You would use either the file resource or template resource, depending on if you wanted simple inline content, or a more complex Erb template:

file '/foo' do
  content "line one\nline two\n"
end

Which Chef resource can I execute multiple lines of BASH code using Chef's sensititve property?

Answered in comments, true and false are lowercase in Ruby. Using True makes Ruby try to look for a const that doesn't exist.

Maintain the file content using chef-client

This isn't what Chef does. It manages the entire content of a file with the file resource. You will need to create your own custom resource if you want a file handling resource that does this. However, given how file manipulation like that would normally work this is going to be pretty specific to the file contents. You really need to encourage that everyone editing a file does so the same way. You shouldn't be partially managing a file with Chef and then letting others manage another part of it a different way. They should update the Chef code appropriately.

If you want people to manage parts individually you can look at partial templates. However, this still requires they manage their portion in a way Chef can import and understand and they aren't manipulating directly on the server.

EDIT: See comments below, this is for the sudoers file and in that case the sudo resource should be used.

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