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Hey guys and welcome back. So in the previous nugget we had discussed the virtual file system

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and at the very end of this nugget, or the end of that nugget should I say, what we did

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was we added a new disk, we partitioned that disk and we actually formatted it with a particular

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file system. Like I say within this nugget right here we're going to be able to use this newly

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created partition and begin practicing how we can manually mount and unmount that file system.

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So the process that I want to walk you through is going to be related to these commands. Now the

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first command I will discuss will be that very first one, the mount command and you can guess

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what this one is going to do. What it's going to do is going to mount a file system but it's also

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going to show you if you just type the command on its own what file systems are currently mounted.

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So it's not just used to make changes i.e. to mount a new file system, this command can also show you

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what is already mounted on the system as well as the corresponding mount options. So let me actually

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just run this command right now, I'll just say the command mount because on its own it's going to

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just simply list the mounted devices. We can see we have a whole bunch of information here. Now let

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me just grep for sd, okay in fact let me just grep for sda so I will clear the screen and do sda

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just so we get a little smaller output so it's easier to focus in on. Now here is the format

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of this output here, we see right here the device in this case here dev sda1 the first partition

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disk one or the one at the top sda5. So that is the first piece of the syntax we're going to see,

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we're going to see the device and then we're going to see the keywords on okay so it doesn't matter

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what we're going to be looking at. The device might change sda1 sda5 but this one here on is going to

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remain the same and I just completely obscured that with my bad drawing on okay. Then what we're

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going to see is the mount point, this is whereabouts in the virtual file system that this device happens

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to be mounted. So if you look at the very top line here and let me just make my pen a little bit

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narrower just so I'm not smudging things up so much notice the first value here you see this

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it just happens to be that forward slash. Now this might be a little bit obscure to you right now

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but it actually just means here this is mounted at this directory here we know that happens to be

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the root directory you know if I happen to go onto my command line and I say cd forward slash and I

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do an ls this is at the root of the tree so let me just go back and I'll reissue my command and then

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we're going to see the keyword type again this is always going to be present so we see it right here

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and we also see it right here in the one below and what the type is going to show us it's going to

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show us the file system type. Now we did talk about some of the file systems that we can actually see

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you mentioned things like ext2 ext3 the top one right here the file system type is ext4 and then

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after this what we're going to see within the brackets we can see right here these are known

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as the mounts options I happen to mention so in this case here we have these different mount options

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what it's saying here is that this is read write meaning that when the system is mounted the disk

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is going to be readable and writable i.e. you can read from the disk and you can maybe create new

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files on this disk because it is writable if there happens to be an error though what is going to

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happen is we're going to try to remount this file system but in read only mode now there are a whole

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bunch of different mount options it's going to be or rather should I say it's going to take

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far too long to cover all of them and you don't have to know all of them in any great depth but

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just understand the basic format of what we're seeing here so if we look at the bottom one here

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we see the device we see the keyword on we see the mount point so in this case here it's in the

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boot directory and within the boot directory it's bootefi to be exact actually so it's not just

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boot it's actually in this directory here if we go into this directory we would be accessing sda1

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now the type of file system mounted here is one called vfat we didn't actually mention this one

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quite just yet again we'll talk about more file systems in a little bit more detail later on

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within this course and then just like we saw before within the brackets we have a whole bunch

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of different mount options that really is the type of format so even if I actually remove the grip

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filter here and just show you the mount look at the format what you see here just take any old one

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here we see the device we see the keywords on we see where it is mounted we see the type and in

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the brackets we see the mount options this is the same for every piece of output we can see here if

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you scroll on up exact same everywhere so that really is the format you can expect when you just

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issue the mount command on its own now here is a very important topic that we really must talk

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about here so when we actually issue the mount command as we know it's showing us what happens to

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be mounted now here is a question how on earth is the mount command getting this information

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does it just know it inherently or is it pulling this information from a particular file well the

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answer is it is indeed pulling that information because all of that information we're talking about

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is stored in a particular location and this is a location we definitely want to be remembering this

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is in the etsy directory and the file is called m tab I like to remember this as the table where

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everything is mounted m tab now whenever a file system is mounted this file right here is updated

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and whenever a file system likewise is unmounted once again this is updated so when we issue this

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mount command and we get this output we're really just pulling information from this file which is

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very frequently updated or I really shouldn't say frequently updated which is updated as soon as

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something is mounted or unmounted so it really just depends how much things have been unmounted

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and mounted now let's actually have a look at this particular file so if we go into the etsy

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directory and I happen to do an ls you can actually see we have m tab right here let me just do an ls

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dash l and scroll on up now you may notice if you have a keen eye the color here is a little bit

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different and we actually have an l at the very end here this means that m tab right here is a sim

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link it's actually pointing to this particular file right here so if I happen to just say cat m tab

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notice this is very close just a slight formatting difference to the output we get with respect to

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the mount command okay again if we happen to look at say for example this one right here we see the

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device we see the mount point we see the type and we also see the mount options again formatted a

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little bit differently we're not going to see the keyword on the keyword type or the brackets around

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the mount point but it really is the same information now if we happen to go into the proc

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directory and I do an ls dash l we're also going to see this other sim link mounts that also points

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to self mounts you see that so we can cat mounts or in fact let me just give it the full name so it's

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a little bit more clear so we cat this file we can see our mount information once again so really

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for the purposes of the examination we want to be remembering that within it say m tab we can get

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mount information as well as from proc forward slash mounts these two locations and we can also get

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mount information directly via the mount command now one thing to just be aware of here because

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this might be a little bit of a gotcha when you happen to use the mount command you can actually

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specify a particular option it's dash n in fact let me just show you here in the man page I say

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man mounts figure down to the n flag we can see here we can use dash n or dash dash no m tab what

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this means is that we can actually mount something without actually updating it say m tab so just be

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aware of this when we happen to use the mount command it is actually possible if someone explicitly

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instructs the mount command to do so to not actually update this particular file so just be aware

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what we see within this file that is a possibility for it to be outdated and again this might be

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when the etsy is a read-only file system that means you actually cannot write within the etsy

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directory therefore you cannot update this particular file if you still want to be able to mount

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something even though you can't write within this directory you could use this particular flag so

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just be aware that that is a possibility now let's get back to the unmounting of a particular file

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now one thing I just want to say directly off the bat because this is a point of confusion very often

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is that the temptation absolutely is to think to use this command here now when I say this command

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I am kind of talking rubbish because this is not a command there is no unmount command the command

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is called you mounts and like I say this can so easily trip people up in the examination you might

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be presented with the syntax of unmounts just drill this into your head that this is not a command

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we want to be using the you mount command the you mount command will unmount something it's just not

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called unmount okay now let's briefly talk about the you mount command now with respect to the you

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mount command it is quite easy to use but you do actually have two different ways you can use this

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command what you can do is once you have a particular file system mounted you can unmount it by saying

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you mount of course and the first option would just be to specify the device you want to unmount

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so let's maybe say forward slash dev forward slash sdb one if that happened to be mounted which right

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now it is not so we could do this specifying the device or depending on where that device was mounted

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let's say it was mounted in a directory called backups within the home ipv0 directory I could

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just see you mount and then the directory home ipv0 and then backups the two different ways to

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unmount either the device we're trying to unmount or the location of where it is currently mounted

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either or will work no problem at all so let's actually see some of this in action then shall we

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now how do we actually see what is mounted and where about the mount point is well we actually do have

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this very useful command this is one you would want to be remembering this is the lsblk command

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this is going to allow it to list our block devices okay now if I happen to use the dash f flag or dash

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dash fs this is also going to give us information about the file system so I can press q and what

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I can do is I can say lsblk dash f check this out right here this is the output we have so we can see

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at the very top we have our first disk sda and we have three different partitions right here on this

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we have sda1 the file type or the file system type should I say is vfat we see the unique or rather

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the universally unique identifier we can see the size how much is in use as well as very crucially

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the mount point like I say if I happen to go into cd boot efi that means transparently we're going

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to be accessing the first partition on this disk now we also have sda5 which would be our first

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logical partition the file system type is ext4 we can see the uuid right here as well as the

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available size how much is in use and notice like I say this is the mount point right here

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in fact let me just redraw that with my squinty line this one right here so the roots file system

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if we go there we are accessing this partition but notice we have sdb this is the disk I created

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and partitioned and happened to format with the as we can see here ext4 file system whereabouts

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is this mounted well in fact as we can see here it is not mounted this command right here can give

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us that information where something is mounted or not mounted now like I say we could if we want we

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could use the mount command and we could grip for sd and try to fish out sdb we can see sda sda1

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sda5 but no sdb me myself I happen to find this output a little bit cleaner so now what I want to

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do is to actually mount this particular file system so some things we have to actually specify here

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so if I just clear the screen and if I go into the mount command I would tell if I could type this

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correctly so have a scroll on down and keep on scrolling there's a lot on this page this is an

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important flag we want to use the t flag or the dash dash types and then we specify the file system

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type so we know from the lsblk command the file system type for this particular device is ext4

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we want to be using that information with the t flag so what I will do here and we want to be using

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super user privileges by the way is you want to say subtle mounts and then the dash t flag and then

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say ext4 that is the file system type now what we want to do is to specify what device do we want

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to mount I will say dev and it's going to be sdb1 and now what I want to do is to give it a mount

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point whereabouts do I want to mount this particular device so what I'm going to do right now just

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by before I issue this command as I will go in to say for example in fact let me just check where

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I am I'm in the home directory here home ipv0 I will make a directory called backups since I've been

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using that in all of my examples I'll go into this and we can see this is an empty directory so I see

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the go back out I will say subtle mounts dash t ext4 the device is dev sdb1 and the location where

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I want to mount this is going to be in home ipv0 and then the backups directory that I've just

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created if I hit enter now I'm going to have to type in my super user password and it seems

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everything is a okay nothing really major has happened but if I do my ls blk command dash f notice

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we have some different outputs here we have information relating to sdb1 we can see the size

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which is available which is one gig how much has been used nothing has been used but more importantly

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whereabouts this is mounted we are in or rather mounted in home ipv0 backups like I say right now

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I am currently on sda5 because I'm working within the root directory if I go in to home ipv0 and then

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into the backups directory and I happen to create a file called file dot txt I do an ls what I've

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actually done is I have ultimately written a file on a different disk on disk 2 partition 1

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you see that and if I go back out I'm now no longer on that disk transparent it doesn't affect our

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experience as the system administrator and like I say if we happen to use the mount command now

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we can see at the very bottom here that indeed mounted we have sdb1 we see the mount points

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we see the type and in brackets we see the mount options similarly if we happen to go into xam tab

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within this one right here same information this is also being updated so like I say if we want to

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unmount this so there is no longer an action we can say sudo you mount in fact let me just show you

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this output one more time remember we have two options we can unmount this by giving the name

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of the device which would be sdb1 or we can specify the location of where it is mounted

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the mount point so I can say sudo you mount dev sdb1 hit enter and notice if I do an lsblk-f

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this is suddenly unmounted and again if I happen to just arrow up I will remount this one more time

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do an lsblk-f we have mounted it once again alternatively as opposed to specifying the actual

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device I can just say sudo you mount and give the mount points to home ipv0 and backups if I

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hit enter same type of deal I can do an lsblk suddenly we have unmounted that file system

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so one thing you'll notice is that what I did is I specified the name of the device as well as where

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I want to mount it what I can also do is just specify the uuid so if I actually just copy this

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value right here as opposed to saying dev sdb1 so I just copy this what I will do is I'll mount it

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using its uuid so I'll say sudo mounts and now I won't have to specify the file system type using

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that dash t flag I can just say dash uppercase u paste in the uuid and then specify whereabouts I

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want to mount this so I can say home ipv0 and then once again in the backups directory if I hit

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enter that should now be mounted I'll do an lsblk dash f and we can see successfully just by using

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the uuid I did not have to specify the file system type or the device the uuid will pull that information

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in automatically now one thing I just want to demonstrate I'll just unmount this device no

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longer mounted if I happen to create a new directory let's just call this new dir and I cd into here

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and what I'll do is I'll create some files in here I'll just say nano my importance file dot

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dxd and just say this is some super important and vital information guess I'll save you okay so

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within this directory right here we have this very important file now what would happen if I try to

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mount a file system into this directory so if I try to mounts I'll say dash t ext4 and I'll mount

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sdb1 and the location is going to be in home ipv0 and into this directory which is not empty notice

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if I do an lsblk dash f it does mount successfully but watch what happens if I go into this directory

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I do an ls where is this important file it's actually gone if I go into my super user and I go

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into lost and found nothing in here either so that important file with that really really important

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information is no longer accessible to me now really the crucial point I want to show you

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is going to lead us into our next video notice we have our file system mounted in this mount

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point right here what would happen if I reboot the system so now I've lost my connection my virtual

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machine is rebooting just give it a moment okay so I've logged back in I'm now going to check my

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mount points once again do an lsblk dash f and look at this you'll notice if you're following along

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you should have the exact same issue suddenly just by rebooting the system the changes we made

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i.e the mounting of this particular partition right here it is no longer mounted that means

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that the changes are not persistent and this is one of the gotchas that you have to be aware of

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when just using the mount command on its own so how on earth are we going to solve this problem

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so that we can make these changes persistent well that's what we're going to be talking about in the

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very next nuggets I hope this has been informative for you and I'd like to thank you for viewing