Linux Command Line

System information Command Description # arch show architecture of machine(1) # cal 2007 show the timetable of 2007 # cat /proc/cpuinfo show information CPU info # cat /proc/interrupts show interrupts # cat /proc/meminfo verify memory use # cat /proc/swaps show file(s) swap # cat /proc/version show version of the kernel # cat /proc/net/dev show network adpters and statistics # cat /proc/mounts show mounted file system(s) # clock -w save date changes on BIOS # date show system date # date 041217002007.00 set date and time - MonthDayhoursMinutesYear.Seconds # dmidecode -q show hardware system components - (SMBIOS / DMI) # hdparm -i /dev/hda displays the characteristics of a hard-disk # hdparm -tT /dev/sda perform test reading on a hard-disk # lspci -tv display PCI devices # lsusb -tv show USB devices # uname -m show architecture of machine(2) # uname -r show used kernel version

Shutdown, Restart and Logout of a system Command Description # init 0 shutdown system(2) # logout leaving session # reboot reboot(2) # shutdown -h now shutdown system(1) # shutdown -h 16:30 & planned shutdown of the system at 16:30 # shutdown -c cancel a planned shutdown of the system # shutdown -r now reboot(1) # telinit 0 shutdown system(3)

Files and Directory Command Description # cd /home enter to directory '/ home' # cd .. go back one level # cd ../.. go back two levels # cd go to home directory # cd ~user1 go to home directory # cd - go to previous directory # cp file1 file2 copying a file # cp dir/* . copy all files of a directory within the current work directory # cp -a /tmp/dir1 . copy a directory within the current work directory # cp -a dir1 dir2 copy a directory # cp file file1 outputs the mime type of the file as text # iconv -l lists known encodings # iconv -f fromEncoding -t toEncoding inputFile > outputFile converting the coding of characters from one format to another # find . -maxdepth 1 -name *.jpg -print -exec convert batch resize files in the current directory and send them to a thumbnails directory (requires convert from Imagemagick) # ln -s file1 lnk1 create a symbolic link to file or directory # ln file1 lnk1 create a physical link to file or directory # ls view files of directory # ls -F view files of directory # ls -l show details of files and directory # ls -a show hidden files # ls *[0-9]* show files and directory containing numbers # lstree show files and directories in a tree starting from root(2) # mkdir dir1 create a directory called 'dir1' # mkdir dir1 dir2 create two directories simultaneously # mkdir -p /tmp/dir1/dir2 create a directory tree # mv dir1 new_dir rename / move a file or directory # pwd show the path of work directory # rm -f file1 delete file called 'file1' # rm -rf dir1 remove a directory called 'dir1' and contents recursively # rm -rf dir1 dir2 remove two directories and their contents recursively # rmdir dir1 delete directory called 'dir1' # touch -t 0712250000 file1 modify timestamp of a file or directory - (YYMMDDhhmm) # tree show files and directories in a tree starting from root(1)

File search Command Description # find / -name file1 search file and directory into root filesystem from '/' # find / -user user1 search files and directories belonging to 'user1' # find /home/user1 -name \*.bin search files with '. bin' extension within directory '/ home/user1' # find /usr/bin -type f -atime +100 search binary files are not used in the last 100 days # find /usr/bin -type f -mtime -10 search files created or changed within 10 days # find / -name *.rpm -exec chmod 755 '{}' \; search files with '.rpm' extension and modify permits # find / -xdev -name \*.rpm search files with '.rpm' extension ignoring removable partitions as cdrom, pen-drive, etc.… # locate \*.ps find files with the '.ps' extension - first run 'updatedb' command # whereis halt show location of a binary file, source or man # which halt show full path to a binary / executable

Mounting a Filesystem Command Description # fuser -km /mnt/hda2 force umount when the device is busy # mount /dev/hda2 /mnt/hda2 mount disk called hda2 - verify existence of the directory '/ mnt/hda2' # mount /dev/fd0 /mnt/floppy mount a floppy disk # mount /dev/cdrom /mnt/cdrom mount a cdrom / dvdrom # mount /dev/hdc /mnt/cdrecorder mount a cdrw / dvdrom # mount /dev/hdb /mnt/cdrecorder mount a cdrw / dvdrom # mount -o loop file.iso /mnt/cdrom mount a file or iso image # mount -t vfat /dev/hda5 /mnt/hda5 mount a Windows FAT32 file system # mount /dev/sda1 /mnt/usbdisk mount a usb pen-drive or flash-drive # mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share mount a windows network share # umount /dev/hda2 unmount disk called hda2 - exit from mount point '/ mnt/hda2' first # umount -n /mnt/hda2 run umount without writing the file /etc/mtab - useful when the file is read-only or the hard disk is full

Disk Space Command Description # df -h show list of partitions mounted # dpkg-query -W -f='${Installed-Size;10}t${Package}n' | sort -k1,1n show the used space by installed deb packages, sorting by size (debian, ubuntu and alike) # du -sh dir1 estimate space used by directory 'dir1' # du -sk * | sort -rn show size of the files and directories sorted by size # ls -lSr |more show size of the files and directories ordered by size # rpm -q -a --qf '%10{SIZE}t%{NAME}n' | sort -k1,1n show the used space by rpm packages installed sorted by size (fedora, redhat and alike)

Users and Groups Command Description # chage -E 2005-12-31 user1 set deadline for user password # groupadd [group] create a new group # groupdel [group] delete a group # groupmod -n moon sun rename a group from moon to sun # grpck check correct syntax and file format of '/etc/group' and groups existence # newgrp - [group] log into a new group to change default group of newly created files # passwd change password # passwd user1 change a user password (only by root) # pwck check correct syntax and file format of '/etc/passwd' and users existence # useradd -c "User Linux" -g admin -d /home/user1 -s /bin/bash user1 create a new user "user1" belongs "admin" group # useradd user1 create a new user # userdel -r user1 delete a user ( '-r' eliminates home directory) # usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1 change user attributes as description, group and other

Permits on Files Command Description # chgrp group1 file1 change group of files # chmod ugo+rwx directory1 set permissions reading (r), write (w) and (x) access to users owner (u) group (g) and others (o) # chmod go-rwx directory1 remove permits reading (r), write (w) and (x) access to users group (g) and others (or # chmod u+s /bin/file1 set SUID bit on a binary file - the user that running that file gets same privileges as owner # chmod u-s /bin/file1 disable SUID bit on a binary file # chmod g+s /home/public set SGID bit on a directory - similar to SUID but for directory # chmod g-s /home/public disable SGID bit on a directory # chmod o+t /home/public set STIKY bit on a directory - allows files deletion only to legitimate owners # chmod o-t /home/public disable STIKY bit on a directory # chown user1 file1 change owner of a file # chown -R user1 directory1 change user owner of a directory and all the files and directories contained inside # chown user1:group1 file1 change user and group ownership of a file # find / -perm -u+s view all files on the system with SUID configured # ls -lh show permits on files # ls /tmp | pr -T5 -W$COLUMNS divide terminal into 5 columns

Special Attributes on files Command Description # chattr +a file1 allows write opening of a file only append mode # chattr +c file1 allows that a file is compressed / decompressed automatically by the kernel # chattr +d file1 makes sure that the program ignores Dump the files during backup # chattr +i file1 makes it an immutable file, which can not be removed, altered, renamed or linked # chattr +s file1 allows a file to be deleted safely # chattr +S file1 makes sure that if a file is modified changes are written in synchronous mode as with sync # chattr +u file1 allows you to recover the contents of a file even if it is canceled # lsattr show specials attributes

Archives and compressed files Command Description # bunzip2 file1.bz2 decompress a file called 'file1.bz2' # bzip2 file1 compress a file called 'file1' # gunzip file1.gz decompress a file called 'file1.gz' # gzip file1 compress a file called 'file1' # gzip -9 file1 compress with maximum compression # rar a file1.rar test_file create an archive rar called 'file1.rar' # rar a file1.rar file1 file2 dir1 compress 'file1', 'file2' and 'dir1' simultaneously # rar x file1.rar decompress rar archive # tar -cvf archive.tar file1 create a uncompressed tarball # tar -cvf archive.tar file1 file2 dir1 create an archive containing 'file1', 'file2' and 'dir1' # tar -tf archive.tar show contents of an archive # tar -xvf archive.tar extract a tarball # tar -xvf archive.tar -C /tmp extract a tarball into / tmp # tar -cvfj archive.tar.bz2 dir1 create a tarball compressed into bzip2 # tar -xvfj archive.tar.bz2 decompress a compressed tar archive in bzip2 # tar -cvfz archive.tar.gz dir1 create a tarball compressed into gzip # tar -xvfz archive.tar.gz decompress a compressed tar archive in gzip # unrar x file1.rar decompress rar archive # unzip file1.zip decompress a zip archive # zip file1.zip file1 create an archive compressed in zip # zip -r file1.zip file1 file2 dir1 compress in zip several files and directories simultaneously

RPM Packages ( Fedora, Red Hat and like) Command Description # rpm -ivh [package.rpm] install a rpm package # rpm -ivh --nodeeps [package.rpm] install a rpm package ignoring dependencies requests # rpm -U [package.rpm] upgrade a rpm package without changing configuration files # rpm -F [package.rpm] upgrade a rpm package only if it is already installed # rpm -e [package] remove a rpm package # rpm -qa show all rpm packages installed on the system # rpm -qa | grep httpd show all rpm packages with the name "httpd" # rpm -qi [package] obtain information on a specific package installed # rpm -qg "System Environment/Daemons" show rpm packages of a group software # rpm -ql [package] show list of files provided by a rpm package installed # rpm -qc [package] show list of configuration files provided by a rpm package installed # rpm -q [package] --whatrequires show list of dependencies required for a rpm packet # rpm -q [package] --whatprovides show capability provided by a rpm package # rpm -q [package] --scripts show scripts started during installation / removal # rpm -q [package] --changelog show history of revisions of a rpm package # rpm -qf /etc/httpd/conf/httpd.conf verify which rpm package belongs to a given file # rpm -qp [package.rpm] -l show list of files provided by a rpm package not yet installed # rpm --import /media/cdrom/RPM-GPG-KEY import public-key digital signature # rpm --checksig [package.rpm] verify the integrity of a rpm package # rpm -qa gpg-pubkey verify integrity of all rpm packages installed # rpm -V [package] check file size, permissions, type, owner, group, MD5 checksum and last modification # rpm -Va check all rpm packages installed on the system - use with caution # rpm -Vp [package.rpm] verify a rpm package not yet installed # rpm -ivh /usr/src/redhat/RPMS/`arch`/[package.rpm] install a package built from a rpm source # rpm2cpio [package.rpm] | cpio --extract --make-directories *bin* extract executable file from a rpm package # rpmbuild --rebuild [package.src.rpm] build a rpm package from a rpm source

YUM packages tool (Fedora, RedHat and alike) Command Description # yum -y install [package] download and install a rpm package # yum localinstall [package.rpm] That will install an RPM, and try to resolve all the dependencies for you using your repositories. # yum -y update update all rpm packages installed on the system # yum update [package] upgrade a rpm package # yum remove [package] remove a rpm package # yum list list all packages installed on the system # yum search [package] find a package on rpm repository # yum clean [package] clean up rpm cache erasing downloaded packages # yum clean headers remove all files headers that the system uses to resolve dependency # yum clean all remove from the cache packages and headers files

DEB packages (Debian, Ubuntu and like) Command Description # dpkg -i [package.deb] install / upgrade a deb package # dpkg -r [package] remove a deb package from the system # dpkg -l show all deb packages installed on the system # dpkg -l | grep httpd show all deb packages with the name "httpd" # dpkg -s [package] obtain information on a specific package installed on system # dpkg -L [package] show list of files provided by a package installed on system # dpkg --contents [package.deb] show list of files provided by a package not yet installed # dpkg -S /bin/ping verify which package belongs to a given file

APT packages tool (Debian, Ubuntu and alike) Command Description # apt-cache search [package] returns list of packages which corresponds string "searched-packages" # apt-cdrom install [package] install / upgrade a deb package from cdrom # apt-get install [package] install / upgrade a deb package # apt-get update update the package list # apt-get upgrade upgrade all of the installed packages # apt-get remove [package] remove a deb package from system # apt-get check verify correct resolution of dependencies # apt-get clean clean up cache from packages downloaded

Pacman packages tool (Arch, Frugalware and alike) Command Description # pacman -S name Install package 'name' with dependencies # pacman -R name Delete package 'name' and all files of it

View file content Command Description # cat file1 view the contents of a file starting from the first row # head -2 file1 view first two lines of a file # less file1 similar to 'more' command but which allows backward movement in the file as well as forward movement # more file1 view content of a file along # tac file1 view the contents of a file starting from the last line # tail -2 file1 view last two lines of a file # tail -f /var/log/messages view in real time what is added to a file

Text Manipulation Command Description # cat example.txt | awk 'NR%2==1' remove all even lines from example.txt # echo a b c | awk '{print $1}' view the first column of a line # echo a b c | awk '{print $1,$3}' view the first and third column of a line # cat -n file1 number row of a file # comm -1 file1 file2 compare contents of two files by deleting only unique lines from 'file1' # comm -2 file1 file2 compare contents of two files by deleting only unique lines from 'file2' # comm -3 file1 file2 compare contents of two files by deleting only the lines that appear on both files # diff file1 file2 find differences between two files # grep Aug /var/log/messages look up words "Aug" on file '/var/log/messages' # grep ^Aug /var/log/messages look up words that begin with "Aug" on file '/var/log/messages' # grep [0-9] /var/log/messages select from file '/var/log/messages' all lines that contain numbers # grep Aug -R /var/log/* search string "Aug" at directory '/var/log' and below # paste file1 file2 merging contents of two files for columns # paste -d '+' file1 file2 merging contents of two files for columns with '+' delimiter on the center # sdiff file1 file2 find differences between two files and merge interactively alike "diff" # sed 's/string1/string2/g' example.txt replace "string1" with "string2" in example.txt # sed '/^$/d' example.txt remove all blank lines from example.txt # sed '/ *#/d; /^$/d' example.txt remove comments and blank lines from example.txt # sed -e '1d' exampe.txt eliminates the first line from file example.txt # sed -n '/string1/p' view only lines that contain the word "string1" # sed -e 's/ *$//' example.txt remove empty characters at the end of each row # sed -e 's/string1//g' example.txt remove only the word "string1" from text and leave intact all # sed -n '1,5p' example.txt print from 1th to 5th row of example.txt # sed -n '5p;5q' example.txt print row number 5 of example.txt # sed -e 's/00*/0/g' example.txt replace more zeros with a single zero # sort file1 file2 sort contents of two files # sort file1 file2 | uniq sort contents of two files omitting lines repeated # sort file1 file2 | uniq -u sort contents of two files by viewing only unique line # sort file1 file2 | uniq -d sort contents of two files by viewing only duplicate line # echo 'word' | tr '[:lower:]' '[:upper:]' convert from lower case in upper case

Character set and Format file conversion Command Description # dos2unix filedos.txt fileunix.txt convert a text file format from MSDOS to UNIX # recode ..HTML <> page.html convert a text file to html # recode -l | more show all available formats conversion # unix2dos fileunix.txt filedos.txt convert a text file format from UNIX to MSDOS

Filesystem Analysis Command Description # badblocks -v /dev/hda1 check bad blocks on disk hda1 # dosfsck /dev/hda1 repair / check integrity of dos filesystems on disk hda1 # e2fsck /dev/hda1 repair / check integrity of ext2 filesystem on disk hda1 # e2fsck -j /dev/hda1 repair / check integrity of ext3 filesystem on disk hda1 # fsck /dev/hda1 repair / check integrity of linux filesystem on disk hda1 # fsck.ext2 /dev/hda1 repair / check integrity of ext2 filesystem on disk hda1 # fsck.ext3 /dev/hda1 repair / check integrity of ext3 filesystem on disk hda1 # fsck.vfat /dev/hda1 repair / check integrity of fat filesystem on disk hda1 # fsck.msdos /dev/hda1 repair / check integrity of dos filesystem on disk hda1

Format a Filesystem Command Description # fdformat -n /dev/fd0 format a floppy disk # mke2fs /dev/hda1 create a filesystem type linux ext2 on hda1 partition # mke2fs -j /dev/hda1 create a filesystem type linux ext3 (journal) on hda1 partition # mkfs /dev/hda1 create a filesystem type linux on hda1 partition # mkfs -t vfat 32 -F /dev/hda1 create a FAT32 filesystem # mkswap /dev/hda3 create a swap filesystem

Filesystem SWAP Command Description # mkswap /dev/hda3 create a swap filesystem # swapon /dev/hda3 activating a new swap partition # swapon /dev/hda2 /dev/hdb3 activate two swap partitions

Backup Command Description # find /var/log -name '*.log' | tar cv --files-from=- | bzip2 > log.tar.bz2 find all files with '.log' extention and make an bzip archive # find /home/user1 -name '*.txt' | xargs cp -av --target-directory=/home/backup/ --parents find and copy all files with '.txt' extention from a directory to another # dd bs=1M if=/dev/hda | gzip | ssh user@ip_addr 'dd of=hda.gz' make a backup of a local hard disk on remote host via ssh # dd if=/dev/sda of=/tmp/file1 backup content of the harddrive to a file # dd if=/dev/hda of=/dev/fd0 bs=512 count=1 make a copy of MBR (Master Boot Record) to floppy # dd if=/dev/fd0 of=/dev/hda bs=512 count=1 restore MBR from backup copy saved to floppy # dump -0aj -f /tmp/home0.bak /home make a full backup of directory '/home' # dump -1aj -f /tmp/home0.bak /home make a incremental backup of directory '/home' # restore -if /tmp/home0.bak restoring a backup interactively # rsync -rogpav --delete /home /tmp synchronization between directories # rsync -rogpav -e ssh --delete /home ip_address:/tmp rsync via SSH tunnel # rsync -az -e ssh --delete ip_addr:/home/public /home/local synchronize a local directory with a remote directory via ssh and compression # rsync -az -e ssh --delete /home/local ip_addr:/home/public synchronize a remote directory with a local directory via ssh and compression # tar -Puf backup.tar /home/user make a incremental backup of directory '/home/user' # ( cd /tmp/local/ && tar c . ) | ssh -C user@ip_addr 'cd /home/share/ && tar x -p' copy content of a directory on remote directory via ssh # ( tar c /home ) | ssh -C user@ip_addr 'cd /home/backup-home && tar x -p' copy a local directory on remote directory via ssh # tar cf - . | (cd /tmp/backup ; tar xf - ) local copy preserving permits and links from a directory to another

CDROM Command Description # cd-paranoia -B rip audio tracks from a CD to wav files # cd-paranoia -- rip first three audio tracks from a CD to wav files # cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force clean a rewritable cdrom # cdrecord -v dev=/dev/cdrom cd.iso burn an ISO image # gzip -dc cd_iso.gz | cdrecord dev=/dev/cdrom - burn a compressed ISO image # cdrecord --scanbus scan bus to identify the channel scsi # dd if=/dev/hdc | md5sum perform an md5sum on a device, like a CD # mkisofs /dev/cdrom > cd.iso create an iso image of cdrom on disk # mkisofs /dev/cdrom | gzip > cd_iso.gz create a compressed iso image of cdrom on disk # mkisofs -J -allow-leading-dots -R -V create an iso image of a directory # mount -o loop cd.iso /mnt/iso mount an ISO image

Networking (LAN / WiFi) Command Description # dhclient eth0 active interface 'eth0' in dhcp mode # ethtool eth0 show network statistics of eth0 # host www.example.com lookup hostname to resolve name to ip address and viceversa # hostname show hostname of system # ifconfig eth0 show configuration of an ethernet network card # ifconfig eth0 192.168.1.1 netmask 255.255.255.0 configure IP Address # ifconfig eth0 promisc configure 'eth0' in promiscuous mode to gather packets (sniffing) # ifdown eth0 disable an interface 'eth0' # ifup eth0 activate an interface 'eth0' # ip link show show link status of all network interfaces # iwconfig eth1 show wireless networks # iwlist scan wifi scanning to display the wireless connections available # mii-tool eth0 show link status of 'eth0' # netstat -tup show all active network connections and their PID # netstat -tupl show all network services listening on the system and their PID # netstat -rn show routing table alike "route -n" # nslookup www.example.com lookup hostname to resolve name to ip address and viceversa # route -n show routing table # route add -net 0/0 gw IP_Gateway configure default gateway # route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1 configure static route to reach network '192.168.0.0/16' # route del 0/0 gw IP_gateway remove static route # echo "1" > /proc/sys/net/ipv4/ip_forward activate ip routing temporarily # tcpdump tcp port 80 show all HTTP traffic # whois www.example.com lookup on Whois database

Microsoft Windows networks (samba) Command Description # mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share mount a windows network share # nbtscan ip_addr netbios name resolution # nmblookup -A ip_addr netbios name resolution # smbclient -L ip_addr/hostname show remote shares of a windows host # smbget -Rr smb://ip_addr/share like wget can download files from a host windows via smb

IPTABLES (firewall) Command Description # iptables -t filter -L show all chains of filtering table # iptables -t nat -L show all chains of nat table # iptables -t filter -F clear all rules from filtering table # iptables -t nat -F clear all rules from table nat # iptables -t filter -X delete any chains created by user # iptables -t filter -A INPUT -p tcp --dport telnet -j ACCEPT allow telnet connections to input # iptables -t filter -A OUTPUT -p tcp --dport http -j DROP block HTTP connections to output # iptables -t filter -A FORWARD -p tcp --dport pop3 -j ACCEPT allow POP3 connections to forward chain # iptables -t filter -A INPUT -j LOG --log-prefix Logging on input chain # iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE configure a PAT (Port Address Traslation) on eth0 masking outbound packets # iptables -t nat -A PREROUTING -d 192.168.0.1 -p tcp -m tcp --dport 22 -j DNAT --to-destination 10.0.0.2:22 redirect packets addressed to a host to another host

Monitoring and debugging Command Description # free -m displays status of RAM in megabytes # kill -9 process_id force closure of the process and finish it # kill -1 process_id force a process to reload configuration # last reboot show history reboot # lsmod display kernel loaded # lsof -p process_id display a list of files opened by processes # lsof /home/user1 displays a list of open files in a given path system # ps -eafw displays linux tasks # ps -e -o pid,args --forest displays linux tasks in a hierarchical mode # pstree Shows a tree system processes # smartctl -A /dev/hda monitoring reliability of a hard-disk through SMART # smartctl -i /dev/hda check if SMART is active on a hard-disk # strace -c ls >/dev/null display system calls made and received by a process # strace -f -e open ls >/dev/null display library calls # tail /var/log/dmesg show events inherent to the process of booting kernel # tail /var/log/messages show system events # top display linux tasks using most cpu # watch -n1 'cat /proc/interrupts' display interrupts in real-time

Others useful commands Command Description # alias hh='history' set an alias for a command - hh = history # apropos ...keyword display a list of commands that pertain to keywords of a program , useful when you know what your program does, but you don't know the name of the command # chsh change shell command # chsh --list-shells nice command to know if you have to remote into another box # gpg -c file1 encrypt a file with GNU Privacy Guard # gpg file1.gpg decrypt a file with GNU Privacy Guard # ldd /usr/bin/ssh show shared libraries required by ssh program # man ping display the on-line manual pages for example on ping command - use '-k' option to find any related commands # mkbootdisk --device /dev/fd0 `uname -r` create a boot floppy # wget -r www.example.com download an entire web site # wget -c www.example.com/file.iso download a file with the ability to stop the download and resume later # echo 'wget -c www.example.com/files.iso' | at 09:00 start a download at any given time # whatis ...keyword displays description of what a program does # who -a show who is logged on, and print: time of last system boot, dead processes, system login processes, active processes spawned by init, current runlevel, last system clock change