Processes & Services

Basic Definitions

Application
Script
Process
Daemon
Thread
Job

Monitoring and Management

command	example	function
fdisk	fdisk -l	disk partitioner -l list disks
df	df -h	filesystem capacity
du	du -sh /var/log	size of each item in directory
uptime	uptime -p	shows urrent time, uptime and load usage % past 1, 5, 15 minutes
top	top -h	display linux processes (human readable)
free	free -h	display amount of free and used system memory (human readable)
lsof	lsof -I :80	list open files (using port 80)
tcpdump	tcpdump -i eth0	capture packets flowing through interface eth0
ps	ps -ef --forest	current processes snapshot (tree diagram)
kill	kill 34448	terminates a process (PID)

top

PID

USER

PR

NI

VIRT

RES

SHR

S

%CPU

%MEM

TIME+

COMMAND

top columns

PID	id
USER	owner
PR	focus priority
NI	the nice value
VIRT	amount of virtual memory in use
RES	amount of resident memory in use
SHR	amount of shared memory in use
S	status of the process
%CPU	share of CPU time since last update
%MEM	share of physical memory in use
TIME+	total cpu time used (hundredths of a second)
COMMAND	name of the command or process

Services & Daemons

systemctl --version	Check if systemd is installed
ps -ef \| grep system	check if systemd is running
systemctl --all	check all running services
systemctl status/stop/start/restart application.service	status/start/stop/restart application.service
systemctl reload application.service	reload the config of a service
systemctl enable/disable application.service	enable or disable at boot
systemctl mask/unmask application.service	enable or disable completely (ignore dependencies)

Logs

/var/log

log directory

Log Examples

boot (overwrites upon boot)
chonyd / ntp
cron
maillog
secure
messages
httpd

Technical Support and Analyse Server

sos report	collect logs and configuration file then transfer to Redhat support server enter case ID compressed archive saved to /var/tmp/sosreport-hostname-caseid-yyyy-mm-dd-filename.tar.xz
cockpit	web based server administration tool sponsored by Red Hat can monitor system resources, add/remove accounts, shutdown system and perform other tasks also available centos redhat ubuntu fedora
ping www.google.com	verify internet connectivity
rpm -qa \| grep cockpit	verify cockpit package is installed
yum/dnf install cockpit -y	install cockpit (Red Hat, CentOS)
apt-get install cockpit	install cockpit (Debian, Ubuntu)
systemctl start/enable cockpit.socket	relies on socket activation to start enable socket listener which watches port 9090 and wakes Cockpit up when someone tries to connect
systemctl status cockpit	verify
systemctl status cockpit.socket	verify
https://192.168.50.164:9090	firewall may need to be disabled (safe for labs) or rule created access the web-interface log in with root or system user can be used to manage everything including terminal access

Back to top