Linux 101 : Gathering information about our system

Linux 101 : Gathering information about our system - whoami, id, ss, ps, ... -

The command "whoami" displays the username we are logged in as:

To be able to see all the users in a Linux system, we can have a look in the "/etc/passwd" file, using the command:

To check the information about the system we are running, we could use the below command:

We could also view the contents of the "/etc/issue" file:

To see more information about the system, we could use the below command:

To check the CPU architecture of the machine, we use:

On Linux, we can display system processes using the below command:

To list all the network interfaces and their IP addresses, we use the below command:

To list all the network connections, including the ports they are listening on and the programs that opened them, we use the below:

We could check the scheduled tasks in a Linux system by looking at the "/etc/cron.*" directories.

The "*" sign is the frequency a task is executed at - daily, weekly, monthly -.

The daily tasks for example are in "/etc/cron.daily".

Remark:

Administrators may also put their scheduled tasks in the "/etc/crontab" file.

To list the applications installed on a system, we could use the below command:

To list all the mounted filesystems on a machine, we use the below command:

To list all the disks on our system, we use the below command:

To display the loaded kernel modules, we use the below command:

To get more information about the above module "e1000", we could use the below command:

To find the SUID programs that running a machine, we could use the below command:

-type f : the command looks for files.

Remark:

The "2>/dev/null" command sends the error messages to the "null" device so they don't appear on the screen.

The SUID bit - when set on a program - allows a user to run a program with the permissions of the owner of the program.

For example, to allow users to change their password, the "passwd" program - which has root privileges - has the SUID bit set.

IT hands-on