The following is a list of commonly used LINUX/UNIX commands which may be of value during your Telnet sessions. Remember that LINUX/UNIX is case sensitive. Options or flags which can be used with a command are placed in [ ]. The [ ] are not part of the command and should not be included in the command that you type.
| login username | allows you to login for a Telnet session |
| passwd | changes your password |
| logout | logs you out of a Telnet session |
| cd | change directory; cd .. moves you backwards to the next higher subdirectory level; cd / moves you to the highest directory level |
| chmod permissions filenames | changes the permissions for a file; permissions should include a letter designating who gets permissions (u for the user, g for the group, o for others, or a for all) followed by a + or – (to give or take away the permission) followed by the kind of permission (r for read access, w for write access, xfor execute if the file is a program or script); the complete command that you type should look like:chmod g-w filename |
| chown user:group filenames | changes ownership of a file |
| clear | clears the screen |
| cp oldfiles newfiles | copies a file; this leaves the old file intact and makes a new copy with a new filename |
| date | tells you the current date and time |
| df | displays how much space on the disks (harddrive partitions) is free |
| du [-a] [-s] directories | tells you how much disk space your files occupy; the -a option displays the space used by each file, not just each directory; the -s option displays the total space used for each directory but not subdirectory |
| finger username@servername | provides information concerning a user; finger without the username@servername will provide information concerning who is using the server at that time |
| help | provides online help; several topics have been included in the help system available on the servers |
| ls [-l] [-a] [-p] [-r] [-t] [-x] | lists the files in a directory; -l displays detailed informtion about each file and directory, including persmissions, owners, size and time/date when the file was last modified; -a option displays all the files and subdirectories including hidden files (with names that begin with a dot); -p displays a slash at the end of each directory name to distinguish them from filenames; -r displays files in reverse order; -t displays files in order of modification time; -x displays the filenames in columns across the screen. |
| lynx servername or URL | Lynx is a text-based, non-graphical web browser for use in Telnet session |
| man [-k keywords] topic | displays the reference manual page about a LINUX command; the –k keywords option allows you to see all man pages that contain that keyword; topic is the command or topic which you want information about |
| mesg [n|y] | lets you control whether other people can use the talk command to interrupt you with on-screen messaging; mesg n will block the interruptions; mesg y will allow interruptions |
| mkdir new_directory | makes a new subdirectory with the name specified by new_directory |
| mv [-i] oldname newname | renames a file or moves it from one filename or directory to another; the -i option tells mv to prompt you before it replaces an existing filename |
| nslookup IP address or server alias | provides conversion of an IP address to an alias of a computer if it is registered in DNS (Domain Name Service) or will provide the IP address for an alias |
| passwd | changes your password |
| pine | a program which allows you to read and send mail; information concerning the use of pine can be found elsewhere in the documentation or by reading the online manual pages for pine ( man pine ) |
| ping IP address or server alias | sends a ping packet to another server; this provides information concerning the time it takes for information to make the round trip to the other computer; it will also tell you whether the other server is on-line at that time |
| ps | displays information about your processes/jobs/programs which are running on the server |
| rm [-i] [-r] filenames | removes or deletes files; the -i option asks you to confirm that you want to delete each file; the -r option is dangerous because it allow you to delete an entire directory and all of the files it contains |
| rmdir directory | removes a directory; you can use the -i and -r options which are described in the rm command |
| tail [-r] [-lines] filename | displays the last few lines of a file; -r displays the lines in reverse order; -lines specifies the number of lines, starting at the end of the file, you want to see |
| talk username@servername | allows you to talk to another user by typing messages to each other on-screen; to prevent someone from talking to you, see the mesg n command |
| touch [-a] [-c] [-m] [date] filenames | changes the date and time for a file without changing the content of the file; -a changes onlyt the date and time the file was last accessed; -c doesn’t create a file if it does not already exist; -m changes only the date and time the file was last modified; date specifies the date and time to give the file in the mmddhhnn format (month, day, hour, minute); touch with a new filename with create a new, empty file. |
| traceroute IP address or server alias | provides information concerning the route which packets must take to get from your computer (the server in this case) to a remote computer/server; typically used to diagnose possible problems in packet routing |
| vi | VI is a text editor. Further information concerning the editing commands for VI can be found in the help document. |
| w | provides information concerning who is logged into the system and some details on how they are connected |
| who | tells you who is using the server at that time |
| write username | sends a message to another person using the system; to prevent someone from writing to you, see the mesg n command |
