Process
ps -auwx - Report a snapshot of the current processes
pstree - Display a tree of processes
pmap - Display/examine memory map and libraries
pidof processname - Find the process ID of a running program
pgrep processname - Look up or signal processes based on name and other attributes
ps -eo pcpu,pid,user,args | sort -k 1 -r | head -10
Performance
iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions
vmstat - Report virtual memory statistics
mpstat - Report processors related statistics
netstat - Print network connections, routing tables, interface statistics, masquerade connections and multicast memberships
free - Display amount of free and used memory in the system
top - provides a dynamic real-time view of a running system
slabtop - display kernel slab cache information in real time
sar - Collect, report, or save system activity information
General Info
uname - print system information
uptime - Tell how long the system has been running
cat /proc/meminfo - Show memory size and usage
runlevel - find the current and previous system runlevel
chkconfig - updates and queries runlevel information for system services
ntsysv - simple interface for configuring runlevels
init, telinit - process control initialization
w - Displays currently logged in users and processes they are running
who - show who is logged on
whoami - Displays user id
chsh - change your login shell
login - sign on
/etc/shells is a text file which contains the full pathnames of valid login shells
set - Display all environment variables in your current environment
id - Display user and all group ids
last, lastb - Listing of most recent logins by users.command
history - Shell command to display previously entered commands
sysreport - collect some detailed information about the hardware which will be used to diagnose problems with the system
hostname - show or set the systemâs host name
domainname - show or set the systemâs NIS/YP domain name
dnsdomainname - show the systemâs DNS domain name
nisdomainname - show or set systemâs NIS/YP domain name
ypdomainname - show or set the systemâs NIS/YP domain name
Kernel
ipcs - List share queues, Shared memory, List Semaphores.
cat /proc/modules List all currently loaded kernel modules.
lsmod - List loaded modules
insmod - Inserts a module into the active kernel
rmmod - Remove a loaded module. Just specify the module name. No ".o" or path necessary.
modprobe - High level handling of loadable modules. Loads module and dependencies.
depmod - Creates dependencies file for a module (used by modprobe)
modinfo - Display information about a kernel module
sysctl - configure kernel parameters at runtime
Network
ifconfig - configure a network interface
setting in /etc/sysconfig/network. Command will change entry in /etc/hosts
mii-tool - view, manipulate media-independent interface status
ethtool - Display or change ethernet card settings
route - show / manipulate the IP routing table
Filesystem
proc - process information pseudo-filesystem
fstab - static information about the filesystems
fsck - check and repair a Linux file system
df - report filesystem disk space usage
du - estimate file space usage
mount - mount a file system
umount - unmount file systems
fdisk - Partition table manipulator for Linux
lsof filesystem - list open files
fuser - identify processes using files or sockets
e2label - Change the label on an ext2/ext3 filesystem
mkfs -t ext2 /dev/ram - build a Linux file system
mke2fs - create an ext2/ext3 filesystem
e2fsck - check a Linux ext2/ext3 file system
tune2fs - adjust tunable filesystem parameters on ext2/ext3 filesystems
dumpe2fs - dump ext2/ext3 filesystem information
partprobe - inform the OS of partition table changes
mkswap - set up a Linux swap area
swapon, swapoff - enable/disable devices and files for paging and swapping
NFS
exportfs - maintain list of NFS exported file systems
showmount - show mount information for an NFS server
nfsstat - print NFS statistics
Files
ls - List directory contents. List file information
fuser - Identify processes using files or sockets
file - Identify file type.
File permission
chmod - Change a file's mode or permissions
umask - Set default file permissions
chgrp - Change a file's group
chown - Change a file's owner
chroot - run command or interactive shell with special root directory
ACL
setfacl - set file access control lists
chacl - change the access control list of a file or directory
getfacl - get file access control lists
User
useradd - Create a new user or update default new user information
usermod - Modify a user account
userdel - Delete a user account and related files
passwd - update a userâs authentication tokens(s)
finger - user information lookup program
chfn - change your finger information
chage - change user password expiry information
users - Show all users logged in.
Group
groupadd - Create a new group
groupmod - Modify a group
groupdel - Delete a group
newgrp - log in to a new group
gpasswd - administer the /etc/group file
grpck - verify integrity of group files
groups - Display groups you are part of
Hardware Info
/usr/bin/lsdev - List devices and info on system hardware. Also IRQ's.(RPM package procinfo)
/sbin/lspci - List all PCI devices (result of probe) Also lspci -vvx and cat /proc/pci
cat /proc/interrupts - List IRQ's used by system and the device using the interrupt.
cat /proc/ioports - List I/O ports used by system.
cat /proc/dma - List DMA channels and device used by system.
cat /proc/cpuinfo - List info about CPU.
hdparm -I /dev/hda - get Harddisk info
Debugging
kill - terminate a process
killall - kill processes by name
pkill - will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout
nice - run a program with modified scheduling priority
renice - alter priority of running processes
ulimit
Log files
closelog, openlog, setlogmask, syslog - control system log
/var/log/messages - system messages
/secure - Logging by PAM of network access attempts
/dmesg - Log of system boot. Also see command dmesg
/boot.log - Log of system init process
/xferlog.1 - File transfer log
/lastlog - Requires the use of the lastlog command to examine contents
/maillog - log from sendmail daemon
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