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Terminal

Architecture

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Important Locations

Location Description
/etc/issue contains a message or system identification to be printed before the login prompt.
/etc/profile controls system-wide default variables, such as Export variables, File creation mask (umask), Terminal types, Mail messages to indicate when new mail has arrived
/proc/version specifies the version of the Linux kernel
/etc/passwd has all registered user that has access to a system
/etc/shadow contains information about the system's users' passwords
/root/.bash_history contains the history commands for root user
/var/log/dmessage contains global system messages, including the messages that are logged during system startup
/var/mail/root all emails for root user
/root/.ssh/id_rsa Private SSH keys for a root or any known valid user on the server
/var/log/apache2/access.log the accessed requests for Apache  webserver

Understanding /etc/passwd format

The /etc/passwd file contains one entry per line for each user (user account) of the system. All fields are separated by a colon : symbol. Total of seven fields as follows.

test:x:0:0:root:/root:/bin/bash

[as divided by colon (:)]

  1. Username It is used when user logs in. It should be between 1 and 32 characters in length.
  2. Password An x character indicates that encrypted password is stored in /etc/shadow file.
  3. User ID (UID) Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-99 are reserved for other predefined accounts. Further UID 100-999 are reserved by system for administrative and system accounts/groups.
  4. Group ID (GID) The primary group ID (stored in /etc/group file)
  5. User ID Info The comment field. It allow you to add extra information about the users such as user’s full name, phone number etc. This field use by finger command.
  6. Home directory The absolute path to the directory the user will be in when they log in. If this directory does not exists then users directory becomes /
  7. Command/shell The absolute path of a command or shell (/bin/bash). Typically, this is a shell. Please note that it does not have to be a shell.

Enumeration