Linux commands

disk space (See also FSlint)
•	ls -lSr	Show files by size, biggest last
•	du -s * | sort -k1,1rn | head	Show top disk users in current dir. See also dutop
•	df -h	Show free space on mounted filesystems
•	df -i	Show free inodes on mounted filesystems
•	fdisk -l	Show disks partitions sizes and types (run as root)
•	rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n	List all packages by installed size (Bytes) on rpm distros
•	dpkg-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n	List all packages by installed size (KBytes) on deb distros
•	dd bs=1 seek=2TB if=/dev/null of=ext3.test	Create a large test file (taking no space). See also truncate
•	> file	truncate data of file or create an empty file

system information (see also sysinfo) ('#' means root access is required)
•	uname -a	Show kernel version and system architecture
•	head -n1 /etc/issue	Show name and version of distribution
•	cat /proc/partitions	Show all partitions registered on the system
•	grep MemTotal /proc/meminfo	Show RAM total seen by the system
•	grep "model name" /proc/cpuinfo	Show CPU(s) info
•	lspci -tv	Show PCI info
•	lsusb -tv	Show USB info
•	mount | column -t	List mounted filesystems on the system (and align output)

file searching
•	alias l='ls -l --color=auto'	quick dir listing
•	ls -lrt	List files by date. See also newest and find_mm_yyyy
•	ls /usr/bin | pr -T9 -W$COLUMNS	Print in 9 columns to width of terminal
	find -name '*.[ch]' | xargs grep -E 'expr'	Search 'expr' in this dir and below. See also findrepo
	find -type f -print0 | xargs -r0 grep -F 'example'	Search all regular files for 'example' in this dir and below
	find -maxdepth 1 -type f | xargs grep -F 'example'	Search all regular files for 'example' in this dir
	find -maxdepth 1 -type d | while read dir; do echo $dir; echo cmd2; done	Process each item with multiple commands (in while loop)
•	find -type f ! -perm -444	Find files not readable by all (useful for web site)
•	find -type d ! -perm -111	Find dirs not accessible by all (useful for web site)
•	locate -r 'file[^/]*\.txt'	Search cached index for names. This re is like glob *file*.txt
•	look reference	Quickly search (sorted) dictionary for prefix
•	grep --color reference /usr/share/dict/words	Highlight occurances of regular expression in dictionary

monitoring/debugging
•	tail -f /var/log/messages	Monitor messages in a log file
•	strace -c ls >/dev/null	Summarise/profile system calls made by command
•	strace -f -e open ls >/dev/null	List system calls made by command
•	ltrace -f -e getenv ls >/dev/null	List library calls made by command
•	lsof -p $$	List paths that process id has open
•	lsof ~	List processes that have specified path open
•	tcpdump not port 22	Show network traffic except ssh. See also tcpdump_not_me
•	ps -e -o pid,args --forest	List processes in a hierarchy
•	ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'	List processes by % cpu usage
•	ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS	List processes by mem usage. See also ps_mem.py
•	ps -C firefox-bin -L -o pid,tid,pcpu,state	List all threads for a particular process
•	ps -p 1,2	List info for particular process IDs
•	last reboot	Show system reboot history
•	free -m	Show amount of (remaining) RAM (-m displays in MB)
•	watch -n.1 'cat /proc/interrupts'	Watch changeable data continuously