Basic Linux Commands for freshers.

• check first the history than the last log-ins, system uptime, last reboot,

# history; last ; uptime ; last reboot;

• Checking Linux General system info:

# uname -a;id;uptime;date;free -mtol;who;cat /proc/cpuinfo;echo $PATH;df -m; sysctl vm;

• Checking Linux General network configuration info

# ip addr show ; ip route show ; ip neigh show; ip rule list; head /etc/resolv.conf

This will show the ip address of the interfaces, the routes, the arp cache , list the routing table rules and our DNS’s.

• Monitor the RAM usage of all processes :

ps -eo pid,ppid,rss,vsize,pcpu,pmem,cmd -ww --sort=pid

• Other Specific health checks

df -i; cat /proc/mdstats;

df -i checking Inodes state, and /proc/mdstats if we have RAID on the box.

• Check for big files and where are the most files on the system:

find . -type f -size +30000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
--  (check for files more then 30000kb)

• Check  the logs if there are any warnings or fatal errors, and other important logs.

zcat messages-* | grep -i warning | less
zcat messages-* | grep -i fatal | less
dmesg | less

• Check full system configuration

sysctl -a