Linux: Useful files

Local user’s database:
/etc/passwd

Local group’s database:
/etc/passwd

SUDO configuration:
/etc/sudoers

Per group SUDO configuration directory SUDO configuration:
/etc/sudoers.d

Per user configuration profile:
$HOME/.profile

Host name IP mapping file:
/etc/hosts

Filesystems mount configuration:
/etc/fstab

SAMBA configuration:
/etc/samba/smb.conf

SSH server configuration:
/etc/ssh/sshd_config

LIBC users/group mapping order:
/etc/nsswitch.conf

TCP/IP services and ports mapping (per IANA):
/etc/protocols
/etc/services

SSSD configuration:
/etc/sssd/sssd.conf 

Kerberos configuration:
/etc/krb5.conf

Kerberos keytab (do not edit, this is automatically generated by Kerberos):
/etc/krb5.keytab

LinuxSecPol cache (do not edit, changes will be re-enforced from the management server if differences are found in any files in the cache):
/dev/shm/linuxsecpol/cache