Symbolic notations used to identify patterns in text literal characters # metacharacters # ^ $ . [ ] { } - ? * + ( ) | \ Most of these have meaning to the shell and must be quoted Metacharacters Character Meaning Usage . Any character ^ Anchor Beginning of the line $ End of the line [ ] Bracket Expression Specify a set of characters at a position ‘^’ negation within brackets ‘-’ range of something within brackets POSIX Character Classes ...
RHCSA Notes # Basic System Management # Linux Filesystem File Permissions Linux Utilities User Management Local User Authentication Files Configuring Networking # 202404240919-private-network 202010261345-subnetting Operating Running Systems # Package Management 20220525072458-rpm 202403200951-dnf 202405121207-systemd 202405081005-cron
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Shell Startup # Shell Startup Files # System-wide Shell Startup Files # /etc/bashrc /etc/profile /etc/profile.d Per-user Shell Startup Files # .bashrc .bash_profile
Sysadmin # OS # Linux Unix Windows Notes # 20220525072201-unix-and-linux-sa-handbook Resources # System Administrator Leveling Matrix Test Your Sysadmin Skills The Operations Report Card Books # The Practice of System and Network Administration Learning # Homelab # Homelab Misc # IT Aphorisms
Syslog # Standard for message logging. Severity Levels # Number Name Description 7 Debug Debug information 6 Information Informational messages 5 Notice Issues of concern that don’t represent a problem 4 Warning Issues that, if not addressed, could become a problem 3 Error Non-urgent errors that need to be addressed when possible 2 Critical Serious errors in secondary subsystem that should be addressed immediatly 1 Alert Serious errors in primary subsystem that should be addressed immediately 0 Emergency Errors that will cause the system to become unusable
systemd # The service manager on most modern Linux distributions. Systemd is the very first process that starts after the kernel is loaded, and it takes care of starting all other processes and services on a Linux system. unit # An item that is managed by Systemd. Different types of units exist: [root@rocky9 ~]# systemctl -t help Available unit types: service mount swap socket target device automount timer path slice scope Overview of units # systemctl Unit Overview Commands ...
systemd-journald # Writes system logging to a binary file. By default only logs since the last boot. journalctl # Most useful journalctl options: Option Use -f Follow the end of journal in real-time, like tail -f -b Show the boot logs -x Explain each log entry in detail -u Filter logs for a specific systemd unit -p Filter logs for messages with a specific priority -e Go to end of logs Conf # Systemd-journald conf: /etc/systemd/journald. ...
Source: The Practice of System and Network Administration Notes # Climbing out of the Hole # Climbing out of the Hole
tree # tree Option Description -a Includes hidden files in the output -d Excludes files from the output -h Displays file sizes in human-friendly format -f Prints the full path for each file -p Includes file permissions in the output