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In this session we are going to learn about RDB persistent. So  I have already logged into the server



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and right now I am in the Home Directory of



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Redis  Admin User



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and if you remember all our Redis File  or Redis Configuration is available under Redis- stable



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Directory. So we are moving inside Redis- stable Directory and here if i do ls-lrt



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I can see Redis.conf File.



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Okay so, this is the file in which we are going to make Configuration related changes to enable RDB



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Snapshotting.  Okay.



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So I'm going to open this file using VI Editor.



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okay.



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So you need to scroll down a bit and you need to reach to the point where it talks about RDB



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okay.



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So right now,  this is the  line which is talking about db file name.



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Okay so this,  db file name is going to be the Snapshot File Name, which is going to get created.



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So by default it is called dumb.rdb.



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So whenever it is going to perform the Snapshotting,



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It is going to create a file which is called dumb.rdb.



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And if you want to change the name you can do that.



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So it is just an Optional Name or if you want to just keep the same name,  you can do that as well.



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So let's say,  I want to change it to



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dump_redis.rdb



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So I have,  I just need to make those changes in the  Configuration File.



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And now you'll be wondering on,  at which location this file is going to get saved.



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Okay.



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So the way to specify that is,  here using these dir parameter.



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So you make a change  here.



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Okay.



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So by default it is pointing to ./



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So by that what it means is,  that whichever place basically you are going to start Redis from,  the



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same directory is going to be used for keeping this dump_redis.rdb



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Now if I do not make any changes and I just want to demonstrate  you,  how it is going to work.



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So let me just save this and exit from here



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and let me go back to the home directory of this user.  Okay.



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If I do pwd,  You can see right now I am in the home directory of Redis Admin and if  i do ls,



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the only directories or  the files you see are, these are the 3 items which you see.



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Okay.



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So I am going to start Redis Server by providing Redis Server and also we need to supply the Configuration



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File Name. So which is available at this location.



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So I'm specifying that and also we are using &



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So start this process as a background.



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Now notice in this case,  the you know, the Redis dump file which is going to be created is,  going to be created



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at this location.



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which  is /home/redisadmin.  Because this is the location from where we are starting Redis



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server and by default for the directory in the Redis.conf  file,  it was specified as./



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So basically it is similar like present working directory.  Okay.



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So once I hit enter and if I do ls,  right now there is nothing available because  Redis has not



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performed any Snapshotting.



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Okay.



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So we also need to specify,  what is this Snapshotting. Mechanism or basically how often Snapshotting should take



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place.



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So if you go and open this file again using VI  editor,  you will also notice,



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I guess we need to go bit up.  Okay.



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All right,  here.



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So by default you see, these are the default configuration which is available here but you can specify



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the configuration based on the approach which you want to follow.



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So in this case using save as a keyword.



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What it is telling to Redis is,  that save or snapshot all the data every 900 seconds.



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If there is at least one key has been changed.



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Okay.



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The second line what it is telling is that  perform a Snapshotting every 300 seconds.



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If there are 10 keys,  which has been added or updated.



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Okay.



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And the third one is telling about



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to perform a snapshot every 60 seconds.



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If there are 10000 Keys has been changed. Okay so all of these three conditions are going to get checked.



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And based on that,  the Snapshotting is going to happen.



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Now what I will do is I'll  create one more piece of line and I will say to



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snapshot every 30 seconds



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and we can save there is 50 keys changed.



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Okay so I have added,  added it as a First Line.



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This can be, you know, any line but usually the practice is you give the higher number on the top and



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then you give  the lower number of Snapshotting at the bottom but that's all about how you want



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to basically document your these things.



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But yeah.



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So that's all for now.



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And if I'm going to save it and again whenever you make any changes in redis.conf



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It is not going to reflect automatically.



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So whatever changes I have done there,  has not been reflected as of now.



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So I need to restart Redis.



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So what I will do is,  I'll just kill this process.



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Now if I see Redis  is not running



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I'll copy paste this Redis  startup command  to start Redis.



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Okay let's do  ls-lrt. So right now,  we do not see any dump file which has been created.



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Now let's start inserting data to Redis



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So I already have a file which is called country code names.



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It is having around 240 plus record. So  I'm going to insert this  to Redis.



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So I'm going to use Mass Insertion Approach or Redis cli  pipe Approach.



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Okay so it has performed the insertion



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and now if I go back to Home Directory and do  ls-lrt. Now you can see we have a dump_redis. rdb File



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Okay so which means,  it has performed the snapshot or taken a snapshot based



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on the



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whatever configuration which we have defined in the Configuration File.



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Okay.



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Now what is the mechanism to restore it.



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So basically our dump file is available here.



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So we need to make sure in this case,  basically when we are starting Redis



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and since in the Redis.conf File, dir property is set to ./   which means present working



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directory.



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So whenever you start Redis, it is going to look for this dump file in the current working directory.



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And then if it is available, it is going to restore everything.



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But if you are starting Redis  from the directory, where this file or dump.rdb file doesn't



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exist,  then it will not be able to restore anything. It would be assuming there is no snapshot available



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and it will not be able to restore any data.



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So let me show you that approach.



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So we'll move to raw_data directory and here if you see, we do not have any



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dump_redis.rdb  file.



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so let me kill  this Redis process.



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Okay.



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We do not have Redis running right now.



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So let's say, if I start Redis from here



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okay.



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So in this case Redis will not be able to restore the data because in the configuration file we have



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defined that dumpfile  is going to be stored at ./ location which is present working directory



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but when I am starting Redis, I am starting from the location where Redis doesn't have or basically there



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is no dump file.  okay or



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There is no snapshot file available, which can be restored.



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So Redis is just going to assume that there is  nothing available to restore and it is just



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going to start without loading any data.



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Okay so let's start this and let's connect to Redis, using Redis cli.  Specify the port



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and if I do dbsize,  you can see I do not have any data and if I do Keys *  you can see we do not have



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any data. The reason being is, we restarted it from a different directory and there was no dumped file available



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to restore.



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So now there are two things which you can do.  Either you can move back to directory where you have this



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dump_redis.rdb file available or let's say you want to restart Redis from any



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other location. In that case you can move this file from this location to the location from where you



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want to start Redis from.



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OK.



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So in this case I'm just going to kill previous  Redis process and then we will be starting Redis from



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this location



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okay.



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So we do not have Redis running  right now and currently I am in the Redis Admin Users Home



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Directory and where we have dump_redis. rdb file available



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So I'm going to start Redis by using Redis-server Command.



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and also going to provide the Configuration File Location and let's start this as a background process.



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So once we do that and when we log in to Redis using Redis cli



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and if I  run dbsize,  this time you can see we have 247 Key Value Pair available in Redis.



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And if I do Keys *  you can see these are the number of keys which are available.



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So basically what it has done is,  it has restored the snapshot which was taken



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OK.



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If you want to see any value available for this key.  You can use Get command and you can see the data



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is available in



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OK.



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So that's one way.



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OK.



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So this is probably not the best approach in the Production.  In the Production,  you always want your



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dump rdb file to be created at a fixed location and also always to be restored from that fixed location



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because in a production you're going to run Redis from a,  through probably some start up Script and you



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don't want all this location to be, you know, Volatile.



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You  want it to be Static.  So let's go back to Redis- stable directory and then move on or  basically



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open the file which we want



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to Edit.



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and then move back to this location,  where it say directory and here you specify the full name or full  path



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of the directory,  where you want to keep all  this snapshotting   file or from where you want to restore



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the snapshot file.



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Okay.



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So here I'm going to specify



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home redis admin.



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So now this is the location or probably I will also specify redis backup.



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Okay,  so this is the  directory  where the Redis is going to basically, you know,  put all the snapshot file or



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this is the location from where it is going to restore the snapshot file.



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I'm not sure if, you know, Redis will automatically create this directory. So let's check that.  I've saved



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it and I'm coming out of this



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Editor and let's kill the existing Redis process.



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Okay so let's remove this dump file,  which was available.



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Okay.



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So we see,  we do not have any of Redis  process running right now.



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And let's start Redis and now I can start Redis from any location.



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It doesn't matter that I need to be on the same location where, you know, Redis  snapshot files



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are going to be kept.



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So I can be in any location,  just to demonstrate you I'm moving to /tmp location.



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You see my current working directory  /tmp and from here we'll be starting that



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Redis.



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So the command is used Redis-server and also specify the location where configuration file



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is available



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and give & in the end



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So this  process runs  as a background process.



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Okay so that's it.



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And if I go back to the, My Home Directory



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and if I do ls-lrt,  here right now we do not see any backup directory created here.



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So let's try to load some data to Redis.



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okay.



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So  there seems to be some issue in starting Redis. So let's check the Logs



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okay.



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So in the Log Directory, we see  there is a error  which is related to,  it cannot find this directory.



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So whatever directory which you provide,  there must exist.



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Redis  is not going to create that directory.



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So let's create this directory



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okay.



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Now if I just clear the screen and show you.



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00:18:20,790 --> 00:18:25,770

So we have created a directory,  which is called Redis_backup



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00:18:27,920 --> 00:18:35,020

and now let's move back to /tmp.  From this location we are going to start Redis Server.



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00:18:52,400 --> 00:18:52,890

okay.



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00:18:52,890 --> 00:18:54,490

Now let's connect to Redis and see if



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00:18:54,560 --> 00:18:55,940

this time we are able to connect



195

00:19:01,030 --> 00:19:01,370

okay.



196

00:19:01,380 --> 00:19:03,600

So this time we can successfully connect to Redis



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00:19:04,250 --> 00:19:07,780

And if I do dbsize,  right now we do not have any data.



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00:19:07,790 --> 00:19:13,590

Because if you remember,  previously we had already removed the dumb file and also we made some Configuration



199

00:19:13,590 --> 00:19:16,150

Changes.



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00:19:16,770 --> 00:19:17,780

OK so



201

00:19:22,230 --> 00:19:23,460

our goal this time is



202

00:19:26,770 --> 00:19:32,380

that once we insert the data,  that snap  or the dumb file should be getting created inside



203

00:19:32,380 --> 00:19:33,440

Redis_backup directory.



204

00:19:33,470 --> 00:19:34,660

So right now if I see



205

00:19:37,530 --> 00:19:39,430

insider  Redis_backup directory,



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00:19:39,440 --> 00:19:40,750

We do not have any file.



207

00:19:40,920 --> 00:19:46,660

OK because we have not performed any insertion or  there is basically no keys have changed and in the



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00:19:46,690 --> 00:19:47,610

Configuration File



209

00:19:47,620 --> 00:19:52,390

We have defined,  how many minimum number of keys should change, before  Redis performs a Snapshot.



210

00:19:52,940 --> 00:19:53,190

OK.



211

00:19:53,230 --> 00:19:56,410

So we have to insert some data



212

00:20:02,900 --> 00:20:06,410

so I'll be inserting data using,  Redis cli pipe method



213

00:20:20,110 --> 00:20:20,380

OK.



214

00:20:20,390 --> 00:20:23,070

So it has inserted around 200.



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00:20:23,390 --> 00:20:28,700

Basically it has made key changes, 249 key changes, and now if I go back to



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Redis_backup  directory,  we can see there is a dumb file is created



217

00:20:46,070 --> 00:20:54,090

and now regardless of the position which we are in,  let's say we move on to, let's say we go back to,



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00:20:54,090 --> 00:21:00,570

/tmp  directory and let's kill the existing Redis process and we will restart Redis.



219

00:21:15,960 --> 00:21:18,460

so right now,  we do not have Redis process running



220

00:21:24,000 --> 00:21:25,740

and I'm going to use this command.



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00:21:28,530 --> 00:21:28,800

OK.



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00:21:28,820 --> 00:21:34,520

So my current working directory is  /tmp and I'm going to start Redis from this location but



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00:21:34,520 --> 00:21:42,740

you will notice unlike the, you know, the way we started previously, when we started previously Redis



224

00:21:42,740 --> 00:21:49,910

from a different location,  then the Redis.dump file present in, we were not able to restore any



225

00:21:49,910 --> 00:21:55,540

data But this time we have specified in Redis.conf directory  that all the backup is going to be



226

00:21:55,540 --> 00:22:01,790

stored in to /home/redisadmin/redis_backup directory.   So it knows



227

00:22:01,790 --> 00:22:07,160

the location and it is going to pick or  scan  for the dump file  from that location and then it is going to



228

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restore.



229

00:22:08,480 --> 00:22:15,820

So let's run this,  to start Redis server and let's connect to Redis  server.



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Okay.



231

00:22:19,650 --> 00:22:24,930

Now if I run dbsize,  you can see I still have 247 keys available



232

00:22:30,320 --> 00:22:37,390

so basically whatever data,  whatever snapshot data was available, it has been successfully restored. Okay



233

00:22:37,440 --> 00:22:43,020

so that's about Redis RDB Approach of Snapshotting



234

00:22:43,260 --> 00:22:47,400

And Restoring.  In next session we are going to learn about AOF