RHEL imporatnt file cheatsheet

The following document is designed to act as a centralized source for all relevant files and some important settings for the RHCSA exam.

General files/Env files

/etc/profile - mother of all environment files
/etc/bashrc - file for all functions and aliases
~/.bash_profile - user specific file where login shell variables can be defined
~/.bashrc - user specific file where subshell variables can be defined
/etc/shadow - file that stores the encrypted password of users among other user information
/etc/passwd - file that stores user info such as id, groups and shell
/etc/login.defs - contains information regarding

sudo

etc/sudoers - file that specifies who can use sudo command. Edit using visudo
/etc/sudoers.d/ - location for dropping in files[username for filename to give specific perms]
/etc/skel/ - files that need to be created for new users

General Networking

/etc/resolv.conf - file that configures the domain name resolver
/etc/hostname - contains the hostname
/etc/hosts - static table lookip for hostnames/maps hostnames to ipaddresses
/etc/nsswitch.conf - config file that determines loop destination and order

NetworkManager

/etc/NetworkManager/NetworkManager.conf - main config file for NetworkManager
/etc/NetworkManager/system-connections/ - The location of persistent profiles.

dnf

/etc/yum.repos.d/ - location for .repos file for establishting repos
/var/log/dnf.rpm.log - history file
/var/log/dnf.log - log file for the dnf command

crond

/etc/cron.allow - if present, specifies which users can access cron services
/etc/cron.deny - if present, specifies which users cannot access cron services

tuned

/etc/tuned - location for all the profiles for the tuned service.

systemd

/etc/systemd/system/ - location for creating a custom file for a custon timers and services
/usr/lib/systemd/system/ - location for all systemd services.

Task Scheduling

systemd timers
- /etc/systemd/system/ - Location for creating .service and .timer files
cron
- /etc/crontab - Location for the main managed config file
- /etc/cron.d/ - Location for drop in files
- /etc/cron.{hourly, daily, weekly, monthly} - Location used for scripts that need to be scheduled on a regular basis
- /var/log/cron - cron logs
anacron /etc/anacrontab - Config file

Temporary file management

systemd-tmpfiles
- /usr/lib/tmpfiles.d/ - rpm provided files for tmp management
- /etc/tempfiles.d/ - custom config
- /run/tmpfiles.d/ - system generated configs

Logging

rsyslog
- /etc/rsyslog.conf - main config file for rsyslog
- /etc/rsyslog.d/ - location for drop-in files
- /var/logs/ - location for most logs
systemd journal settings - /var/log/journal - location for journals to be stored after persistence is enabled. Set ownership to 2755
- For persistence
  - /etc/systemd/journal.conf
    - Storage=auto
      - /var/log/journal
    - Storage=volatile
      - /run/log/journal
    - Storage=none
logrotate
- /etc/logrotate.conf - main config files for logrotate
- /etc/logrotate.d/

disk management

fstab
- /etc/fstab - file for configuring mounting permanence
/etc/systemd/generator - location for all the mount files that are being generated by systemd

boot files

/etc/default/grub - file specifying boot properties
/boot/efi/EFI/redhat/grub.cgf - file containing boot information for a RHEL installation using EFI
/boot/grub2/grub.cfg - file containing boot information for a RHEL installion using mbr
/.autorelabel - file used by SELinux for relabeling the filesystem.

ssh

/etc/ssh/sshd_config - main config file for sshd

SELiux

/etc/systemconfig/seliux - config file for SELinux . Link to config file in /etc/selinux/
/var/log/audit/audut.log - contains SELinux permission logs. Look for AVC

containers

/etc/containers/registeries.conf - config file for containers
/proc/self/uid_map - used along with podman unshare to verify UID mapping
~/.config/systemd/user - directory to generate a .service file from podman in.