Table of Contents

Linux



Commands

Linux Commands Cheat Sheet popular
bash
OpenSSL popular Check SSL Certificate Expiration Date :
openssl s_client -connect example.com:443 </dev/null 2>/dev/null|openssl x509 -text|grep -E "Not|Issuer:|sha"


Configuration

ssh popular Create Key Pair : ssh-keygen -t rsa -C "comment"
- How to use ProxyCommand with ssh
- ssh portfoward
X11 Forwarding
sudo /etc/sudoers
su /etc/pam.d/su
SELinux /etc/selinux/config
Check Command : getenforce
ntp /etc/ntp.conf
/etc/sysconfig/ntpd
ntpdate -b -u IPADDRESS
cron /var/spool/cron/USER
/etc/cron.d/FILE
snmp
LDAP
PAM
iptables


Log

Syslog

syslogd (RHEL5/centos5)
rsyslog (RHEL6,7/centos6,7)
journald (RHE7/centos7)
syslog-ng How to check Configuration:
syslog-ng -s -f file

Log Rotate

logrotate /etc/logrotate.conf
logrotate -d /etc/logrotate.d/httpd ← -d : test. don't lotate

Note


International Configuration

LANG /etc/sysconfig/i18n
TimeZone /etc/localtime
/etc/sysconfig/clock
keyboard /etc/sysconfig/keyboard

Note


Install/Software

tftp Configuration : /etc/xinetd.d/tftp
Check : tftp IPADDR
pxe (preboot execution environment)
kickstart
yum popular
RHN (After RHEL5) LANG=C rhn_register --nox --proxy=http://192.168.0.10:9999


Network

Linux Network Configuration and Command


Disk

Linux Disk Configuration and Command


Performance

Linux Performance


Kernel

Kernel Parameter sysctl -a ← check
/etc/sysctl.conf
User Resource ulimit -a ← check
/etc/security/limits.conf

Note