Unix Tools
Bash Commands
uname -a ## Get the Kernel Version
lsb_release -a # Release or Distibution info
cat /etc/SuSE-release # Suse Linux Version Check
cat /etc/debian_version # Debian Version check
Basic Commands to know the Server status
uptime # it will shows how long the system has been running
hostname # System Host Name
hostname -i # To Display to the ip address of the Host, Linux based distribution
man hier # File system hierarchy Description
last reboot # to know the system reboot history
Hardware informations
Kernel Detected HW
dmesg # Detect Hardware and Boot messages
lsdev # Info about the installed Hardware like PCI Card
dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8 # Read BIOS
Linux
cat /proc/cpuinfo # CPU Model
cat /proc/meminfo # Hardware Memory
grep MemTotal /proc/meminfo # Physical Memory
watch -n1 'cat /proc/interrupts' # watch changecable interrupts
free -m # To know the used & free memory ( -m for MB)
cat /proc/devices # Configured devices
lspci -tv # PCI Device info
lsusb -tv # USB Device info
lshal # List all devices with properties
dmidecode # DMI/SMBIOS: hw info from the BIOS
Free BSD
sysctl hw.model # CPU Model
sysctl hw # More information about hardware
sysctl hw.ncpu # No. of active CPU's Installed
sysctl vm # Memory Usage
sysctl hw.realmem # Hardware Memory (Physical)
sysctl -a | grep mem # Kernel memory settings and info
sysctl dev # Configured devices
pciconf -l -cv # PCI Device info
usbdevs -v # USB Device info
atacontrol list # ATA Device info
camcontrol devlist -v # SCSI Device info
Load, Statistics and Messages
Folowing Commands are useful to find out what is going on the system realtime.
top # display & update the top CPU processes
mpstat 1 # display processors related statistics
vmstat 2 # virtual memory statistics
iostat 2 # I/O statistics - 2sec intervals
systat -vmstat 1 # system statistics - 1sec intervals
systat -tcp 1 # tcp connections (try also -ip)
systat -netstat 1 # active network connections - BSD
systat -ifstat 1 # network traffic through active interfaces - BSD
systat -iostat 1 # CPU and Disk throughput - BSD
ipcs -a # info on system V interprocess
tail -n 500 /var/log/messages # Last 500 Kernel/syslog messages
tail /var/log/warn # System Warnings messages see syslog.conf
Users
id # To display the active user ID with login & group
last # To know the last logins on the server
who or w # Who is logged on the server currently in simple type "w"
groupadd admin # Adding group "admin"
useradd -c "Dhanesh Kumar" -g admin -m colin # Creating user "Dhanesh Kumar", with "admin" group
usermod -a -G <group> <user> # Adding existing user to the group - Debian Based
groupmod -A <user> <group> # Adding existing user to the group - Suse Linux
userdel dhanesh # delete the user "dhanesh" (linux / Solaris)
adduser dhanesh # FreeBSD add user joe (interactive)
rmuser dhanesh # FreeBSD delete user joe (interactive)
pw groupadd admin # Use pw on FreeBSD
pw groupmod admin -m newmember # Add a new member to a group
pw useradd dhanesh -c "Dhanesh Kumar" -g admin -m -s /bin/tcsh
pw userdel dhanesh; pw groupdel admin
/etc/shadow - Encrypted passwords are stored
Temporarily prevent system logings for all user except ROOT user, with nologin.
echo "Apologies no login now" > /etc/nologin #(linux)
echo "Apologies no login now" > /var/run/nologin #(FreeBSD)
Limits in Linux
Some application requires higer limits on open files and sockets (like a proxy web server, database). The default limits are usually too low.
Shell/Script
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