Linux Essentials - Managing Users

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now let's get started with today's video [Music] [Music] hello again everyone and welcome back to learn linux tv in today's video we're going to take a look at user management in linux one of the most important things that you'll learn how to do because well you have to keep track of your users on your linux servers and that's exactly what i'm going to show you the basics of in this video i'll show you how to add users how to remove users how to set their password and some other stuff as well so let's go ahead and get started alright so here i am on my popos system this is my thinkpad x1 extreme laptop but it doesn't really matter which distribution you're using or what computer you have there will be some variations here and there but for the most part when it comes to adding and removing users it's the same on each distribution now if i do run across something that i think might be different from one distro to another i'll be sure to point it out let's go ahead and open up a terminal and get started and here's my terminal complete with a ridiculously large font i just want to make sure that everyone is able to see the content and understand what i'm doing let's go ahead and get started just like with most things when it comes to linux there's more than one way that we can do just about everything and adding users is no exception to that especially in my case considering i'm using desktop linux i don't even need to use the command line at all however using the command line is completely universal there's many different desktop environments and each one is going to have a different process for adding users but each linux distribution is going to have access to the user add command which is the command that we'll be using for the majority of this video and when it comes to servers it's very common that linux servers won't have a desktop environment another reason to learn the command line anyway like i mentioned the command that we will use to add a new user to our system is the user add command and considering that we'll be making changes to the system we'll either need to be logged in as root or we can simply use sudo in order to run this command with root privileges which is required for any command that's going to make changes to the server and of course adding a user is making a system-wide change so of course we're going to need root privileges or we could just use sudo if we have that installed and most of you should after we type user add we type the name of the user that we actually want to add to the system and that will complete the command before we actually add a new user let's take a look at some foundational concepts first before we get started on that and the first thing that i recommend you do is understand which users you have on your system already what some people do is they will simply list the contents of the home directory because generally speaking most users will have his or her own home directory underneath home and you can see mine right here so i have a home directory and we can glean from this that my user j is on the system now you probably already knew that because well you can see my username right here in the prompt so you already knew that at least my user account existed here and here it is but checking the contents of the home directory is not really the best way to find out how many users or which users in particular you have already on your server i mean from the output here you'd probably assume that my user account is the only user on the system but actually that's not true what i want to do right now is make sure that you're aware of the existence of a very special file and that's the etsy password file password is abbreviated that's not a typo that's actually what the file is named but i'll refer to it as etsy password which is common in the linux community even though it's abbreviated so the cat command is just going to show me the contents of that file and you can see that the text is wrapped here so what i'm going to do is just lower the font size a bit and as you can see we have quite a few users on this system not just mine we have many more we see my user right here and each user is on their own line so for example if i was to again cap the contents of the etsy password file and then i pipe it into the wc command which stands for word count and that's a bonus command it wasn't even supposed to be part of the video but you're welcome anyway what i'm going to do is add the dash l option to the word count command what that's going to do is give me the count of how many lines there are so as you can see from the output there's 44 users on the system so definitely a lot more than the one you saw earlier when i listed the contents of slash home and in this file every user on the system has its own line in this file the first column shows the name of the user and then there's other columns that follow after that i'll go over this file in a little bit more detail later on but at this point in the video i want to make sure that you're aware of this file that you're aware that it exists and that you're aware of what its purpose is its purpose is to contain a listing and the options that are associated with the user accounts on your server but either way it's just a good idea to know whether or not the user is on the system already and by checking the contents of this file we can determine that now one of the things i'm going to do is cap this out again that i'm going to grep so that way the only line of output that it's going to produce is just the one line that contains my user account and what i want to point you to is this number right here where it shows 1000. now again i'll go over this file in more detail later i think it's a good idea to understand what this number is that number refers to the user id aka uid every user has his or her own uid as you can see here the uid of my user is 1000. most distributions of linux actually ask you to create a user account during the installation process and that first user is well pretty much almost always given the uid of 1000. i'll talk more about uids a bit later but that's just another thing that i wanted you to be aware of anyway let's go back to the user ad command after all that's why we're here in the first place we want to know how to add and remove users and the user add command as the name would imply is the command that we would use to add a user to the system i'm logged in as j so i can't really use this command like i mentioned earlier without sudo or just logging in as root so i'm going to add sudo to the command and then at the end i'm going to give it the name of a user i want to create so i'm going to tell it to create a user with the name of foxmolder so for all of you x-files fans out there yes that was an easter egg and the x-files was actually my favorite sci-fi series growing up i loved watching that every sunday night great times anyway what i'm going to do right now is press enter and now it's asking me for my password my user password to verify that i have access to the sudo command and it didn't say anything but it also doesn't appear to have failed either so if i cap the contents of etsy password again let's see what happens and as you can see the very last line in this file shows that user was created now if you recall the uid for my user was uid 1000 for fox moulder that user got uid 1001. now something to keep in mind is that when you add a user to a linux system it's going to assign the next available uid to that user now my user already had assigned the uid of 1000. so that uid is no longer available when i created the account fox molder it just incremented it by one 1001 that's the uid that it was provided as you can see here now you'll notice from the output that there's some uids here that are much lower than 1000 for example 122 121 and so on on most distributions of linux normal user accounts basically user accounts that are associated with interactive logins or basically user ids that are going to be used by a human those are given uids 1000 and above uids below 1000 are considered system accounts and i'll talk a little bit more about system accounts in a few minutes but i just wanted you to be aware of that distinction we have user accounts we also have system user accounts and the user add command by default adds normal user accounts now i added a user for foxmolder we did that with the previous command that we entered let's also list the contents of the home directory and see whether or not that user has a home directory underneath home and it doesn't why is that now depending on your distribution it might have actually created a home directory for that user on my end it didn't this is one thing that actually does differ from one distribution to another each distribution is going to set their own defaults for the user add command so on your end it might have created a home directory on my end well i wasn't so fortunate so let's take a quick detour here and what i'm going to do is point you to another file and that file is the etsy default user ad file now i'm not going to go over this particular file in too much detail but basically what it does is sets the defaults for user ad each distribution is free to supply their own version of this particular file so as you can see here we have shell equals slash bin slash sh if you want to use a different default shell then you'll change it right here but basically this file just sets the defaults and again it's going to be different from one distribution to another and it's entirely possible that on your distribution you may not even have this file at all now all i want at this point is for you to be aware that this file exists what you might think that i'm going to recommend is that you customize this file with the defaults that you prefer but i'm not going to do that instead i recommend that you be explicit say what you mean and mean what you say so even if your distribution did create a home directory here i still recommend that you tell the user add command specifically that you want a home directory now on your end that might be redundant if it already created a home directory for the user that you created then why should you bother and add a redundant option to tell it to create a home directory when it already did now it's a good idea to basically be explicit when it comes to linux include all the options that's especially true when you're writing scripts because you want your scripts to be portable maybe you have a script that you want to run on multiple distributions if that's the case you'll probably want the same output every time that script runs so if you are using the user add command as part of a script you'll probably want to add all the appropriate options to ensure that all the user accounts that you create are always created the same way and i recommend that you be explicit not just when you're creating scripts but basically just get in the habit of always doing that so what i want to do is re-add the user but i want to add the user with a home directory this time but that requires another detour because the user already exists i could create another user but what i'm going to do instead is take this opportunity to show you how to remove a user account so to remove a user account you can use the user dell command the user delete command however you want to say it we'll need to use sudo and then we give it the name of the user that we want to delete but be very careful here when you run a command like this on a linux system the linux system is going to make the assumption that you know what you're doing so just make sure that you're typing the username that's actually the user you want to delete just be very careful so we created a user earlier named foxmolder i'm going to delete that user account maybe moulder got abducted by aliens or something i don't know but we're going to remove them from the system and that's it now that user didn't even have a home directory to begin with but the thing is though if that user did have a home directory they would probably still have a home directory here because of the user delete command that doesn't delete the home directory for the user when you delete a user by default just keep that in mind we'll return to that in a few minutes but anyway we can see here that that particular user account is gone so let's go ahead and add that user back to the system and at the same time make sure that a home directory is also created for that user when we create the user itself and this is the command right here that we used earlier so what i'm going to do is add the dash m option i'll press enter no output just like last time but the difference at least in my case is that the user actually has a home directory right now we see that right here the line is wrapped a bit you get the idea that user does indeed have a home directory we added the dash m option which is what you see here that specifically tells user ad that we want a home directory when we create this user so let's talk about removing the user again but this time also removing the home directory as well and again we see that user does indeed have a home directory and earlier when we remove this account the first time this is the command that we used right here so to remove a home directory we add the dash r option to this command that's going to like i mentioned remove the user account and also their home directory now before i actually press enter here i do want to mention that before you start removing a home directory for a user for example if you are working at a company you'll want to make sure that you should remove their home directory before you actually do it for example if an employee leaves the company that employee supervisor might need access to their files in order to finish any projects that they might have been working on but if you delete their files well they can't do that perhaps more importantly a lot of companies out there they have requirements for how long to retain their employees data and if you're actually working in a company it's extremely important that you ask hr or whoever it is you ask there what the retention policy is for employee data you'll want to make sure that you are in compliance with any policies that might exist maybe a company might have a policy where they have to retain user records for a few years if you delete a user account with their home directory then you are not in compliance now if your company does not have a policy when it comes to user data retention or data retention in general it's actually one of those things that should definitely be drafted let somebody know anyway i'm going to press enter we can ignore this message right here about the mail spool that's beyond the scope of this video that is a normal message though so nothing to be concerned with we can check the contents of the home directory again and that home directory is in fact gone another thing that i want to show you guys is how to set a password for a user because when we added the fox molder user it didn't even ask us what we wanted the password to be for that user in fact the user had no password at all now what i'm going to do is just add the user back to the system i'm going to add it with the home directory so nothing different i'll just press enter user has a home directory and the user is on the system so let's take a look at how we set a password for the user and to set a password for a user or even change our own password for that matter we have a dedicated command the past wd command now if i entered this by itself right now it's going to assume that i want to change the password for the user that i'm currently logged in with so if you had a user for example that came to you and said how do i change my password you would ask them to run the passwd command you don't even need to get involved they can change their own password there's nothing for you as the administrator to do in this regard other than to know that the passwd command exists and i'm going to actually use it right now i'm going to make it fail on purpose though and the reason why is because i don't want to change my password right now but the first thing that it does is it asks you for your current password which i've entered and then it asks you for your new password what do you want your new password to be which i've entered and then you enter it again and it's telling me that the passwords don't match and that was intentional if the passwords did match then the password i chose right then and there would become my password so that's how you change the password for the user that you're logged in with but actually i brought that up in regards to setting a password for another user so for example if you have someone that's going to start logging into your linux server you can set a temporary password for them and then ask them to change it in a future video we'll be going over password expiration but we're going to omit that right now just to keep things simple so to change a password for another user you can type sudo because in order to change a password for another user you do need root privileges or at least access to sudo in order to be able to do that then you can run passwd and then the name of the user that you want to change the password for or in this case you want to set the password so i'll type the name of the user right here now notice that it didn't ask me for the user's current password you might think that the reason why it didn't ask me was because the user didn't even have a password we didn't even set a password but if you have access to sudo or the root user it's never going to ask you for the user's current password i mean root is pretty much like god mode if you've ever played doom for example it's the all-powerful account that can do basically everything so root doesn't need to know the password of the user to change or set the password so even if the user already had a password it doesn't care you're setting the password and anyone that has access to root has permission to set a password for another user so i'm going to type it in right now and again and it said password updated successfully so i was able to add a password for the fox motor user now let's go ahead and see an example of creating a system user a system user is very useful when you are doing any kind of automation for example maybe you have an accounting department and you need to run a financial report for them every week that sounds tedious to me and to be honest with you doing a financial report that doesn't really excite me and if you're like me you'll probably want to automate that report so you'll never be bothered to do it but if you're going to automate something like a process or some sort of task then it makes sense to not use your user account for it create a system user and actually you can use a system user with cron to run a scheduled job which is the best way to do it now i'll be covering kron in a future video in this series go ahead and check the playlist to see if it's already there but for now just keep in mind that system users are useful when you want something to run in the background and it's not something that's associated to any one person so let's go ahead and add a system user right now so again it's sudo and then user add and we're going to use dash r and that dash r option actually allows us to designate that we want to create a system user specifically not a normal user and what i'm going to do is call the system user assist user just like that i'll press enter and what i'm going to do is cap the contents of etsy password again and i'm going to grep for sysuser because i only want to see that one line and we see it right here now notice that the uid is 998. it doesn't start with 1000. earlier when we created a user that user was assigned uid 1001 but this user was actually assigned a uid of less than a thousand and that's generally the case normal user accounts will be provided a uid of a thousand or greater and then system users will generally be provided a uid of less than one thousand and that distinction doesn't really matter so much other than you can deduce that a user is most likely a system user based on the uid in my case i'm using a desktop distribution of linux and most of the time desktop distributions will not show a system user on the login screen now that does vary from one distribution to another but generally speaking most distributions will not show you ids on the login screen that are under 1000. that's important because if it did show you ids that are under a thousand then in my case there would be probably around 44 user accounts shown on the login screen and that's very messy but anyway at this point i just want you to be aware of the dash r option and just keep in mind that that allows you to create a system user and a system user again is a user that generally doesn't log in interactively and is used for things that are going to run in the background schedule tasks processes things like that now that actually completes the main part of this video the whole goal was to show you the basics of user management and i've already showed you how to add a user how to remove a user and some options with the user add command now of course you could just type man and then user add and then you get a bunch of options here as far as some of the additional things that you can do with that command but as far as the basics are concerned which was the actual purpose of this entire video were covered there but i'm not going to end the video just yet there's one more thing that i want to show you guys and as i promised earlier in the video i told you that i would go over the contents of the etsy password file to help you guys understand it better let's go ahead and do that right now now as you recall the etsy password file that contains a listing of all the users on the system there's quite a few lines there so what i'm going to do is lower the font size a bit just to make sure you can see everything hopefully that's not too small we have several different columns on each line and each column is separated by a colon now the first column is the username no surprise there the second column which is this one right here that just refers to the password actually it's a little bit more complicated than that but it essentially means that we have an encrypted password in use here and nowadays we don't really use any other kind of password we always use hashed passwords which is what this refers to it just means that the password for this user is hashed it's not shown here in some ways that's a carryover from the olden days which is why i'm not going to go into too much detail on that but you'll probably almost if not always see an x in that field continuing we have the uid right here as i talked about earlier the next field is the group id i've already explained what a uid is earlier in the video and a gid or group id is essentially the same thing but for groups i'll be covering groups in a separate video so don't worry about that right now this field here that is the user information field and you might see that referred to as the geckos field g-e-c-o-s so it looks like that but i like to refer to it as the user information field and it's most commonly used for the first and last name as you see here that user information field is completely optional it's perfectly fine to go ahead and skip it and you'll actually see it skipped in other user accounts and other lines you'll see like two colons together that just means that that information isn't there it's blank continuing on we have the home directory for the user in my case slash home slash j that's where my home directory is so it's essentially telling the linux system where to find the home directory for that user the last column here that refers to the shell that is designated for that user when a user logs in their shell is activated in my case slash bin slash bash that's the shell that i'm going to be using when i log in so for example if i type echo then dollar sign and then shell in all caps you can see that my shell is slash bin slash bash and that was set right here and again this is the shell that's going to start up as soon as i log in now you will see other things here instead of slash bin sh or bin bash for example user s bin no login and you'll see other variations of this as well user aspen no login means well that user is not going to be able to log in and when it comes to system users we really don't want them to log in and generally speaking system users are not associated to a human being so there's no reason for them to interactively log in and they don't have to log in in order to run reports run command scripts or anything like that often people will use system accounts to automate things like i mentioned earlier and that's essentially all this is user spin no login means basically what it says when that user tries to log in even if you did set a password for that user they'll be denied it's going to attempt to run user spin no login which is basically going to deny the login now let's go ahead and take a look at the etsy shadow file now real quick you'll recall that i mentioned that we have an x rate here for most if not all the users and that x refers to the fact that that user has a hashed password it's almost always going to be the case we really don't want to store the user's password in plain text in the etsy password file we would rather hash it and store it somewhere else so if we take a look at the etsy shadow file now as an aside you will need sudo in order to view this file unlike the etsy password file as you can see i was able to run cat etsy password with no sudo at all but i can't get away with that when it comes to etsy shadow so i will add sudo now just like with the etsy password file with the etsy shadow file we have a bunch of different columns on each line and each column is separated by a single colon on the left we have the username and that's the username right here and to make it a little bit easier i'm going to grep for my user account here just to get it down to one line makes it a little bit easier but in the first column again we have the username in the second column which is actually ridiculously long we have the actual hash for the password now this isn't my actual password it's just a hash of my password that's an important distinction so moving on we have this field right here and that number refers to the number of days since the unix epoch that the password was last changed for those that aren't already aware the unix epoch is january 1st of 1970. therefore we could read that column as a password having last been changed that many days after the unix epoch so in this case 18 807 days the fourth column tells us how many days are required to pass before the user will be able to change their password again in this example the user can change their password well anytime and they can do that because the number of days is set to zero zero means any time this column right here refers to how many days until a password change is required in this case 99 999 days since the unix epoch will pass until i'm required to change my password so i guess it may as well be infinite in a future video we'll explore user password expiration so don't worry about that too much right now so here we have number seven and this field refers to how many days until the user will be reminded to change their password so in this case if the user's password is going to expire within seven days it's going to show them a message on the shell but well i mean there's quite a few days until this password is going to expire so even though it shows 7 i'm probably never going to see that message now here we have several columns that are not set at all so the next field would have showed us how many days until the user password is going to be locked i never actually set a time for the password to be locked so that's not set we also have a field that would normally show us how many days until the account is disabled but that's not set either now i went over the last fields here fairly quickly and that's because you really don't need to memorize that i mean you can if you want to but we have a dedicated command that we would use to lock a user account to set a password expiration and things like that and more importantly a dedicated command we can use to check that information without having to remember those fields so i wouldn't worry about it too much we'll get to that when we cover password expiration in a future video so there you go there's actually additional concepts that we could have gone over in this video when it comes to user management but i decided to save those for future videos again check the playlist for this series because other videos on user management might already exist and if they don't i will create those for you very soon make sure you subscribe so you'll be the first to see those videos as soon as they're out regardless thank you so much for watching i really appreciate it and i'll see you next time [Music] you

Channel: LearnLinuxTV

Views: 10,172

Rating: 4.9788361 out of 5

Keywords: Linux, Tutorial, Howto, Guide, Learn Linux, open source, gnu/linux, users, linux users, user management, add user, remove user, useradd, userdel, /etc/passwd, /etc/shadow, linux commands, linux tutorial, user tutorial, linux tutorial for beginners, command line, linux essentials, linux command line tutorial, gnu/linux (operating system), linux tutorial for beginners 2021, linux tutorial 2021, linux command to know, open source software, linux permissions, linux command line, how to

Id: 19WOD84JFxA

Length: 32min 58sec (1978 seconds)

Published: Wed Jul 14 2021