Ubuntu环境下Nagios集成check_postgres插件遇Peer认证失败求助

Hey there! I’ve run into this exact issue before, so let’s break down why this is happening and how to fix it quickly.

Why the Error Happens #

PostgreSQL’s peer authentication checks if your system username matches the PostgreSQL username you’re trying to connect as. When you run su postgres and execute the plugin, you’re using the postgres system user which maps directly to the default postgres PostgreSQL user—so it works. But Nagios runs all its checks under the nagios system user, which doesn’t have a matching PostgreSQL user or permission to connect via peer auth.

Step-by-Step Fixes #

1. Create a PostgreSQL User for Nagios

First, we need a PostgreSQL user that matches the nagios system user:

• Switch to the postgres system user:

  su postgres
  

• Create the nagios PostgreSQL user (add -P if you want to set a password right away, which we’ll need for password-based auth later):

  createuser -P nagios
  

• Grant basic connection permissions to the user (adjust based on what checks you need):

  psql -c "GRANT CONNECT ON DATABASE postgres TO nagios;"
  

2. Update PostgreSQL's pg_hba.conf

Next, tell PostgreSQL to allow the nagios user to connect. Open the pg_hba.conf file (location varies by PostgreSQL version, usually /etc/postgresql/<your-version>/main/pg_hba.conf):

sudo nano /etc/postgresql/14/main/pg_hba.conf

Add this line near the top of the local connections section:

local   all             nagios                                  md5

Note: Using md5 means PostgreSQL will use password authentication. If you strictly want peer auth, ensure the nagios system user exists (it should if Nagios is installed) and replace md5 with peer.

Save the file and restart PostgreSQL to apply changes:

sudo systemctl restart postgresql

3. Configure the Plugin in Nagios

Update your Nagios command definition to use the new nagios PostgreSQL user. For example:

define command {
    command_name    check_postgres
    command_line    $USER1$/check_postgres -U nagios -d postgres
}

To avoid hardcoding passwords, create a .pgpass file for the nagios user:

• Switch to the nagios user:

  su nagios
  

• Create the file:

  nano ~/.pgpass
  

• Add this line (replace <your-password> with the one you set earlier):

  localhost:5432:*:nagios:<your-password>
  

• Set strict permissions (required by PostgreSQL):

  chmod 600 ~/.pgpass
  

4. Test the Check

Before reloading Nagios, verify the plugin works as the nagios user:

su nagios
/usr/lib/nagios/plugins/check_postgres -U nagios -d postgres

If it returns a normal status (like POSTGRES_CONNECT OK), you’re ready to go.

5. Reload Nagios

Finally, apply the command changes by reloading Nagios:

sudo systemctl reload nagios

That should resolve the peer authentication error! Let me know if you hit any snags.

内容的提问来源于stack exchange，提问作者Mat