Linux References
A running guide of Linux commands focused on Red Hat Based Distros that I often forget.
SSH Control Characters
As with all SSH control characters all commands must follow a return character.
~.
Kill the current SSH connect. Great for when something hangs and you’re waiting for a timeout.~#
List all forwarded SSH connections.
Logging
journal --since 9:00 --until 12:00
Show system logs between those timesjournal -u postfix --since yesterday -f
Show all postfix logs since yesterday and follows logsjournal -k -n 20
Kernel messages since last boot limiting to 20 messages
tmux
<c-b> :setw synchronize-panes (on/off)
Synchronize text input on all panes.
sysstat
sar -d -f /var/log/sa/sa15 -s 19:00:00 -e 21:00:00
Get diskstats on the last 15th of the month between the hours of 7pm and 9pm.
nmap
nmap -sP -oG scan-results.txt 10.0.0.0/24,10.0.1.0/24
Quick ping scan of two subnets with greppable outputs written to a file.nmap -sA -F -Pn <host>
TCP ACK scan common ports without an initial ping scan. Good for mapping out a stateful firewall.nmap -sU -A -v <host>
Scan all UDP ports with an additional service discovery scan and with verbose output. Can be combined with a TCP scan using the-sS
flag.nmap --iflist
Wrapper around ifconfig and ip. Very useful for quick access to important info.nmap --script ssl-enum-ciphers -p 443 <hostname>
Cycles through all the ciphers the webserver will respond too on port 443. Ensuring vulnerable SSL protocols aren’t used.
tcpdump
tcpdump 'host 10.0.1.2 and (dst port 80 or 443)' -w dump.pcap
Capture traffic destine for 80/443 for host IP 10.0.1.2 writing raw output to a file.src
andnet
can be used as well.
Git
Merging in other’s changes
git fetch # Checkout repo metadata
git checkout <feature/branch> # Change working HEAD to branch to be merged
git fetch # Fetch branch to be merged
git rebase master # Flatten branch and set master as base. Use -i squash or delete commits.
git checkout master # Change head to master branch
git merge <feature/branch> # Move master branch up to HEAD
git push origin master # Push new rebased master to origin server
Rebase onto master
git checkout -b <feature/new_branch> # Create new feature branch
... Do Some Work ...
git pull --rebase origin master # Shortcut for fetch + rebase
Often Forgotten Linux Utilities
lsof -c ssh -i TCP:22
Filter to TCP port 22 and command strings with ssh.lsblk
andfindmnt
Tools for finding hardware block devices and filesystems.dmesg -n 1
ordmesg -D
Suspend logging to console until next reboot. Change can be made permanent inrc.local
.
Related References
Selinux Guide
How to manage Selinux at scale