install: linux: add system upgrade recommendation (#688)

Signed-off-by: lecaros <[email protected]>

Author: lecaros

installation/linux/debian.md

@@ -34,6 +34,11 @@ Now let your system update the _apt_ database:
 $ sudo apt-get update
 ```
 
+{% hint style="info" %}
+We recommend upgrading your system (```sudo apt-get upgrade```). This could avoid potential issues with expired certificates.
+{% endhint %}
+
+
 ## Install TD Agent Bit
 
 Using the following _apt-get_ command you are able now to install the latest _td-agent-bit_:

installation/linux/raspbian-raspberry-pi.md

@@ -32,6 +32,11 @@ Now let your system update the _apt_ database:
 $ sudo apt-get update
 ```
 
+{% hint style="info" %}
+We recommend upgrading your system (```sudo apt-get upgrade```). This could avoid potential issues with expired certificates.
+{% endhint %}
+
+
 ## Install TD-Agent Bit
 
 Using the following _apt-get_ command you are able now to install the latest _td-agent-bit_:

installation/linux/ubuntu.md

@@ -40,6 +40,11 @@ Now let your system update the _apt_ database:
 sudo apt-get update
 ```
 
+{% hint style="info" %}
+We recommend upgrading your system (```sudo apt-get upgrade```). This could avoid potential issues with expired certificates.
+{% endhint %}
+
+
 ## Install TD-Agent Bit
 
 Using the following _apt-get_ command you are able now to install the latest _td-agent-bit_: