| COMMAND | DESCRIPTION |
| System information |
| arch | show architecture of machine |
| uname -r | show used kernel version |
| dmidecode -q | show hardware system components - (SMBIOS / DMI) |
| hdaparm -i /dev/hda | displays the characteristics of a hard-disk |
| hdparm -tT /dev/sda | perform test reading on a hard-disk |
| 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) |
| lspci -tv | display PCI devices |
| lsusb -tv | show USB devices |
| date | show system date |
| cal 2007 | show the timetable of 2007 |
| date 041217002007.00 | set date and time - MonthDayhoursMinutesYear.Seconds |
clock -w
| save date changes on BIOS |
| Shutdown, Restart of a system and Logout |
| shutdown -h now | shutdown system |
| init 0 |
| telinit 0 |
| shutdown -r hours:minutes & | planned shutdown of the system |
| shutdown -c | cancel a planned shutdown of the system |
| shutdown -r now | reboot |
| reboot |
| logout | leaving session |
| Files and Directory |
| cd /home | enter to directory '/ home' |
| cd .. | go back one level |
| cd ../.. | go back two levels |
| cd | go to home directory |
| cd ~utente | go to home directory |
| cd - | go to previous directory |
| pwd | show the path of work 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 |
| mkdir dir1 | create a directory called 'dir1' |
| mkdir dir1 dir2 | create two directories simultaneously |
| mkdir -p /tmp/dir1/dir2 | create a directory tree |
| rm -f file1 | delete file called 'file1' |
| rmdir dir1 | delete directory called 'dir1' |
| rm -rf dir1 | remove a directory called 'dir1' and contents recursively |
| rm -rf dir1 dir2 | remove two directories and their contents recursively |
| mv dir1 new_dir | rename / move a file or 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 |
| ln -s file1 lnk1 | create a symbolic link to file or directory |
| ln file1 lnk1 | create a physical link to file or directory |
| touch -t 0712250000 fileditest | modify timestamp of a file or directory - (YYMMDDhhmm) |
| File search |
| 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 |
| mount /dev/hda2 /mnt/hda2 | mount disk called hda2 - verify existence of the directory '/ mnt/hda2' |
| umount /dev/hda2 | unmount disk called hda2 - exit from mount point '/ mnt/hda2' first |
| fuser -km /mnt/hda2 | force umount when the device is busy |
| 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 |
| 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 |
| Disk Space |
| df -h | show list of partitions mounted |
| ls -lSr |more | show size of the files and directories ordered by size |
| du -sh dir1 | estimate space used by directory 'dir1' |
| du -sh * | sort -rn | show size of the files and directories sorted by size |
| rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n | show space used by rpm packages installed sorted by size (fedora, redhat and like) |
| dpkg-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n | show space used by deb packages installed sorted by size (ubuntu, debian and like) |
| Users and Groups |
| groupadd group_name | create a new group |
| groupdel group_name | delete a group |
| groupmod -n new_group_name old_group_name | rename a group |
| useradd -c "Nome Cognome" -g admin -d /home/user1 -s /bin/bash user1 | create a new user 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 |
| passwd | change password |
| passwd user1 | change a user password (only by root) |
| chage -E 2005-12-31 user1 | set deadline for user password |
| pwck | check correct syntax and file format of '/etc/passwd' and users existence |
| grpck | check correct syntax and file format of '/etc/group' and groups existence |
| newgrp group_name | log in to a new group to change default group of newly created files |
| Permits on File - use "+" to set permissions and "-" to remove |
| ls -lh | show permits |
| ls /tmp | pr -T5 -W$COLUMNS | divide terminal into 5 columns |
| 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 |
| chown user1 file1 | change owner of a file |
| chown user1 -R directory1 | change user owner of a directory and all the files and directories contained inside |
| chgrp gruppo1 file1 | change group of files |
| chown user1:gruppo1 file1 | change user and group ownership of a file |
| find / -perm -u+s | view all files on the system with SUID configured |
| chmod u+s /bin/file_eseguibile | set SUID bit on a binary file - the user that running that file gets same privileges as owner |
| chmod u-s /bin/file_binario | 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/comune | set STIKY bit on a directory - allows files deletion only to legitimate owners |
| chmod o-t /home/comune | disable STIKY bit on a directory |
| Special Attributes on file - use "+" to set permissions and "-" to remove |
| 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 |
| 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 |
| unrar 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 |
| 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 |
| unzip file1.zip | decompress a zip archive |
| RPM Packages - Fedora, Red Hat and like |
| 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_name.rpm | 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_name | obtain information on a specific package installed |
| rpm -qg "System Environment/Daemons" | show rpm packages of a group software |
| rpm -ql package_name | show list of files provided by a rpm package installed |
| rpm -qc package_name | show list of configuration files provided by a rpm package installed |
| rpm -q package_name --whatrequires | show list of dependencies required for a rpm packet |
| rpm -q package_name --whatprovides | show capability provided by a rpm package |
| rpm -q package_name --scripts | show scripts started during installation / removal |
| rpm -q package_name --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_name | 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 |
| rpm2cpio package.rpm | cpio --extract --make-directories *bin* | extract executable file from a rpm package |
| rpm -ivh /usr/src/redhat/RPMS/`arch`/package.rpm | install a package built from a rpm source |
| rpmbuild --rebuild package_name.src.rpm | build a rpm package from a rpm source |
| YUM packages updater - Fedora, RedHat and like |
| yum install package_name | download and install a rpm package |
| yum update | update all rpm packages installed on the system |
| yum update package_name | upgrade a rpm package |
| yum remove package_name | remove a rpm package |
| yum list | list all packages installed on the system |
| yum search package_name | find a package on rpm repository |
| yum clean packages | 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 |
| dpkg -i package.deb | install / upgrade a deb package |
| dpkg -r package_name | remove a deb package from the system |
| dpkg -l | show all deb packages installed on the system |
| dpkg -l | grep httpd | show all rpm packages with the name "httpd" |
| dpkg -s package_name | obtain information on a specific package installed on system |
| dpkg -L package_name | 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 updater - Debian, Ubuntu e like |
| apt-get install package_name | install / upgrade a deb package |
| apt-cdrom install package_name | install / upgrade a deb package from cdrom |
| apt-get update | update all deb packages installed on system |
| apt-get remove package_name | remove a deb package from system |
| apt-get check | verify correct resolution of dependencies |
| apt-get clean | clean up cache from packages downloaded |
| View file content |
| cat file1 | view the contents of a file starting from the first row |
| tac file1 | view the contents of a file starting from the last line |
| more file1 | view content of a file along |
| less file1 | similar to 'more' command but which allows backward movement in the file as well as forward movement |
| head -2 file1 | view first two lines of a file |
| 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 |
| cat file_test | [operation: sed, grep, awk, grep, etc] > result.txt | syntax to elaborate the text of a file, and write result to a new file |
| cat file_originale | [operazione: sed, grep, awk, grep, etc] >> result.txt | syntax to elaborate the text of a file and append result in existing file |
| 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 |
| sed 's/stringa1/stringa2/g' example.txt | replace "string1" with "string2" in example.txt |
| sed '/^$/d' example.txt | remove all blank lines from example.txt |
| sed '/ *#/d; /^$/d' example.txt | remove comments and blank lines from example.txt |
| echo 'esempio' | tr '[:lower:]' '[:upper:]' | convert from lower case in upper case |
| sed -e '1d' result.txt | eliminates the first line from file example.txt |
| sed -n '/stringa1/p' | view only lines that contain the word "string1" |
| sed -e 's/ *$//' example.txt | remove empty characters at the end of each row |
| sed -e 's/stringa1//g' example.txt | remove only the word "string1" from text and leave intact all |
| sed -n '1,5p;5q' example.txt | view from 1th to 5th row |
| sed -n '5p;5q' example.txt | view row number 5 |
| sed -e 's/00*/0/g' example.txt | replace more zeros with a single zero |
| cat -n file1 | number row of a file |
| 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 |
| 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 |
| 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 |
| 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 |
| Character set and Format file conversion |
| dos2unix filedos.txt fileunix.txt | convert a text file format from MSDOS to UNIX |
| unix2dos fileunix.txt filedos.txt | convert a text file format from UNIX to MSDOS |
| recode ..HTML < page.txt > page.html | convert a text file to html |
| recode -l | more | show all available formats conversion |
| Filesystem Analysis |
| badblocks -v /dev/hda1 | check bad blocks in 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 |
| 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.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 |
| dosfsck /dev/hda1 | repair / check integrity of dos filesystems on disk hda1 |
| Format a Filesystem |
| mkfs /dev/hda1 | create a filesystem type linux on hda1 partition |
| 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 -t vfat 32 -F /dev/hda1 | create a FAT32 filesystem |
| fdformat -n /dev/fd0 | format a floppy disk |
| mkswap /dev/hda3 | create a swap filesystem |
| SWAP filesystem |
| 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 |
| 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 |
| 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 |
| 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 |
| 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 |
| find /var/log -name '*.log' | tar cv --files-from=- | bzip2 > log.tar.bz2 | find all files with '.log' extention and make an bzip archive |
| 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 |
| CDROM |
| cdrecord -v gracetime=2 dev=/dev/cdrom -eject blank=fast -force | clean a rewritable cdrom |
| 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 "Label CD" -iso-level 4 -o ./cd.iso data_cd | create an iso image of a directory |
| 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 |
| mount -o loop cd.iso /mnt/iso | mount an ISO image |
| cd-paranoia -B | rip audio tracks from a CD to wav files |
| cd-paranoia -- "-3" | rip first three audio tracks from a CD to wav files |
| cdrecord --scanbus | scan bus to identify the channel scsi |
| Networking - LAN and WiFi |
| ifconfig eth0 | show configuration of an ethernet network card |
| ifup eth0 | activate an interface 'eth0' |
| ifdown eth0 | disable an interface 'eth0' |
| 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) |
| dhclient eth0 | active interface 'eth0' in dhcp mode |
| route -n | show routing table |
| route add -net 0/0 gw IP_Gateway | configura 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 |
| hostname | show hostname |
| host www.google.com | lookup hostname to resolve name to ip address and viceversa |
| ip link show | show link status of all interfaces |
| mii-tool eth0 | show link status of 'eth0' |
| ethtool eth0 | show statistics of network card 'eth0' |
| netstat -tup | show all active network connections and their PID |
| netstat -tupl | show all network services listening on the system and their PID |
| tcpdump tcp port 80 | show all HTTP traffic |
| iwlist scan | show wireless networks |
| iwconfig eth1 | show configuration of a wireless network card |
| Microsoft Windows networks - SAMBA |
| 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 |
| mount -t smbfs -o username=user,password=pass //winclient/share /mnt/share | mount a windows network share |
| IPTABLES - firewall |
| 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 "DROP INPUT" | logging sulla chain di input Logging on chain input |
| 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 |
| top | display linux tasks using most cpu |
| ps -eafw | displays linux tasks |
| ps -e -o pid,args --forest | displays linux tasks in a hierarchical mode |
| pstree | mostra un albero dei processi sistema Shows a tree system processes |
| kill -9 ID_Processo | force closure of the process and finish it |
| kill -1 ID_Processo | force a process to reload configuration |
| lsof -p $$ | display a list of files opened by processes |
| lsof /home/user1 | displays a list of open files in a given path system |
| strace -c ls >/dev/null | display system calls made and received by a process |
| strace -f -e open ls >/dev/null | display library calls |
| watch -n1 'cat /proc/interrupts' | display interrupts in real-time |
| last reboot | show history reboot |
| lsmod | display kernel loaded |
| free -m | displays status of RAM in megabytes |
| 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 |
| tail /var/log/dmesg | show events inherent to the process of booting kernel |
| tail /var/log/messages | show system events |
| Other useful commands |
| 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 |
| man ping | display the on-line manual pages for example on ping command |
| whatis ...keyword | displays description of what a program does |
| mkbootdisk --device /dev/fd0 `uname -r` | create a boot floppy |
| gpg -c file1 | encrypt a file with GNU Privacy Guard |
| gpg file1.gpg | decrypt a file with GNU Privacy Guard |
| 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 |
| ldd ssh | show shared libraries required by ssh program |
| alias hh='history' | set an alias for a command - hh = history |
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