User accounts, authentication and messages
/etc/passwd Local authentication user file
/etc/shadow Local authentication password file
/etc/group Local system groups
/etc/gshadow Local system group authentication password file
/etc/sudoers Config file for SUDO
/etc/issue Text shown before a user logs in
/etc/motd Message of the day shown after a user logs in
/etc/pam.d/ Config files for PAM system authentication
/etc/profile System wide environment
/etc/profile.d/ System wide environment additional files
/etc/bashrc System wide aliases and functions
~./bash_profile User specific environment and startup programs
~/.bashrc User specific aliases and functions
Disks, scheduled tasks and other
/etc/fstab Filesystem table that lists all filesystems to be mounted
/etc/exports Exported filesystems for NFS
/etc/nsswitch.conf Determines name resolution order
/etc/hosts Static name resolution
resolv.conf External DNS servers
/etc/crontab System wide scheduled tasks
/etc/cron.d/ System wide scheduled tasks additional files
/etc/anacrontab System wide anacron scheduled tasks
/etc/cron.allow, /etc/cron.deny Allow/Deny access control for cron jobs
/etc/hosts.allow, /etc/hosts.deny Allow/deny files for ssh (and other tcpwrappers tools)
/etc/ssh/ Config files and keys for ssh
/etc/sysconfig/ System hardware config files