Get it Now! mp3 file Contact Details: Email: questions@rootsmart.com Voicemail: (206) 734-4825 Skype: rootsmart Vote for us at Podcast Alley Content: Today we are starting a many part series on running linux we are going to step through linux and show you how to use it, and what it all means today we are going to be talking about users. so when you first start up your linux box you are probably greeted with a login box you login to your user account and everything is good until you have to do any system changes. then you have to login as root do you know why this is? it is mainly a way to keep Linux secure Everything in a Unix environment has permissions these permissions tell the system if you are allowed to access the file if you are allowed to access the file what rights do you have? to view the permissions of a file, if you are running a Desktop environment you can right click on the file and choose properties, or at the command line type ls -l file as you can see in the graphical environment, there are three user types and under each type is three abilities the abilities are read, write, or execute the three user types are User, Group, Other User is the owner of the file or directory that basically means who created it if it is in your home folder you probably created it if it is in the etc folder or any of the system folders root probably created it only the owner can edit permissions all users belong to at least one group by default you belong to your own separate group you can easily put you and a number of other users into a group that way you can have multiple users with the same permissions also the group that has takes effect is the owners group to create a group type groupadd groupname then to add a user to a group type adduser user group it is very easy, just make sure the owner of the file is in that group the last user type is other this is basically everyone else if you are not the owner, or are not in the owners group you are other so now we have three types of group permissions the first is read read means that if it is directory you can see what is in it, but not change anything the second is write this says if a user and create a new file in a directory or delete files or it says if you can edit text files or any other file the last is execute this says if a person can go into the directory, or if a person can execute and program now changing all of these is easy to do if you have a graphical interface in KDE or GNOME just right click on the files, go to permissions and edit away it is that easy with the command line it is a little harder, let me explain first type ls -l filename to see what the current permissions are remember that r is read, w is write, and x is execute you will see something like -rwxr-xr-x the first charecter is whether it is a directory this will have a d if it is the next three are the permissions for the user then after those three are the three permissions for the group then other to edit permissions in the command line we use the chmod command if you want to do something that affects all users, lets say stop anyone from executing it type chmod a-x filename a stands for all and the -x or minus x clears the x bit so if you want to add the ability to read for group type chmod g+r filename as you can see + adds a permission, and - removes a permission also you use u for user, g for group, and o for other if you would like to add more than one permission to more than one user type you just type chmod ug-wx filename this will remove the write and execute bit from the user and group so that is pretty easy, lets go on to these number that you might see if you want permissions of rwxr-xr-x you type chmod 755 filename this works out like this the read bit is worth 4 the write bit is worth 2 and the execute bit is worth 1 so: 4+2+1=7 4+0+1=5 4+0+1=5 that makes sense a very common triplet is 777 this is for all access to all user types it works out like this 4+2+1=7 4+2+1=7 4+2+1=7 so that is all with user permissions. I hope this helped Technorati Tags: Linux, Users, RootSmart.com

[ Sun, 23 Apr 2006 15:46:25 -0400 ]

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