1 00:00:00,300 --> 00:00:02,009 In this lesson, we're going to learn 2 00:00:02,009 --> 00:00:03,600 about partitions and their use 3 00:00:03,600 --> 00:00:05,880 in the Linux operating system. 4 00:00:05,880 --> 00:00:08,910 Aside from managing user access to your Linux systems, 5 00:00:08,910 --> 00:00:10,710 one of the most foundational tasks 6 00:00:10,710 --> 00:00:13,020 is the management of data storage. 7 00:00:13,020 --> 00:00:15,570 There are many different ways to divide, format, 8 00:00:15,570 --> 00:00:17,250 or otherwise organize the data 9 00:00:17,250 --> 00:00:18,990 that's going to be stored on your systems. 10 00:00:18,990 --> 00:00:22,050 And Linux gives you many different tools for doing this. 11 00:00:22,050 --> 00:00:24,750 Using these tools, you'll ultimately make it easier 12 00:00:24,750 --> 00:00:27,720 for authorized users to work with data. 13 00:00:27,720 --> 00:00:30,030 There are many different types of storage devices 14 00:00:30,030 --> 00:00:32,670 that are supported by the Linux operating system. 15 00:00:32,670 --> 00:00:34,770 Common types include hard disk drives, 16 00:00:34,770 --> 00:00:37,470 they use magnetic storage technology to store your data. 17 00:00:37,470 --> 00:00:38,760 Solid-state drives, 18 00:00:38,760 --> 00:00:40,950 they use non-mechanical, solid-state technology 19 00:00:40,950 --> 00:00:42,300 to store your data. 20 00:00:42,300 --> 00:00:45,120 USB thumb drives, they use flash memory technology 21 00:00:45,120 --> 00:00:46,290 to store your data. 22 00:00:46,290 --> 00:00:47,880 And external storage drives, 23 00:00:47,880 --> 00:00:50,010 they use several different types of technologies, 24 00:00:50,010 --> 00:00:51,540 and usually connect to the computer 25 00:00:51,540 --> 00:00:52,860 through a peripheral interface 26 00:00:52,860 --> 00:00:55,410 rather than being internally connected. 27 00:00:55,410 --> 00:00:57,060 In Linux, devices are referred to 28 00:00:57,060 --> 00:00:59,790 as either block or character devices. 29 00:00:59,790 --> 00:01:02,580 Block devices are things like storage devices, 30 00:01:02,580 --> 00:01:04,230 these are things like hard drives, 31 00:01:04,230 --> 00:01:06,720 solid-state drives, and USB drives. 32 00:01:06,720 --> 00:01:08,520 And all of these can be read from 33 00:01:08,520 --> 00:01:11,130 or written to in blocks of data. 34 00:01:11,130 --> 00:01:13,410 Character devices on the other hand are devices 35 00:01:13,410 --> 00:01:16,200 like keyboards, mice, serial ports, 36 00:01:16,200 --> 00:01:18,630 and other things like that that can read from 37 00:01:18,630 --> 00:01:21,993 or write to streams of data one character at a time. 38 00:01:22,860 --> 00:01:24,900 A file system is a data structure 39 00:01:24,900 --> 00:01:26,940 that's going to be used by an operating system 40 00:01:26,940 --> 00:01:30,240 to store, retrieve, organize, and manage files 41 00:01:30,240 --> 00:01:32,910 and directories on a given storage device. 42 00:01:32,910 --> 00:01:35,670 It also maintains information about the data 43 00:01:35,670 --> 00:01:37,020 such as the date of creation 44 00:01:37,020 --> 00:01:39,330 and the modification of individual files, 45 00:01:39,330 --> 00:01:41,820 the size of the files on that storage device, 46 00:01:41,820 --> 00:01:42,960 the type of files, 47 00:01:42,960 --> 00:01:45,540 and the permissions associated with those files. 48 00:01:45,540 --> 00:01:48,060 But the operating system does not interpret 49 00:01:48,060 --> 00:01:50,310 the data contained in the files itself 50 00:01:50,310 --> 00:01:54,090 because this task is handled by specific applications. 51 00:01:54,090 --> 00:01:57,240 The file systems vary depending on several different things, 52 00:01:57,240 --> 00:01:59,130 such as the purpose of the file systems, 53 00:01:59,130 --> 00:02:01,740 the information they store about the individual files, 54 00:02:01,740 --> 00:02:03,210 and the way they store data 55 00:02:03,210 --> 00:02:05,100 as well as the data security mechanisms 56 00:02:05,100 --> 00:02:06,930 that are going to be implemented. 57 00:02:06,930 --> 00:02:09,870 Linux systems support several different types of systems, 58 00:02:09,870 --> 00:02:14,870 including FAT, ext2, ext3, ext4, XFS, and BTRFS. 59 00:02:17,340 --> 00:02:20,220 These file systems can be used for varying situations 60 00:02:20,220 --> 00:02:22,590 depending on your specific user needs. 61 00:02:22,590 --> 00:02:24,960 FAT or the File Allocation Table 62 00:02:24,960 --> 00:02:27,120 is an older file system that is compatible 63 00:02:27,120 --> 00:02:29,070 with many different operating systems, 64 00:02:29,070 --> 00:02:33,600 including all versions of Unix, Windows, and Mac OS X. 65 00:02:33,600 --> 00:02:35,580 It does not provide the same capabilities 66 00:02:35,580 --> 00:02:37,350 as more modern file systems, 67 00:02:37,350 --> 00:02:38,550 and it's typically going to be used 68 00:02:38,550 --> 00:02:40,380 when you need to maintain compatibility 69 00:02:40,380 --> 00:02:43,200 between all these different operating systems. 70 00:02:43,200 --> 00:02:46,257 Ext2 on the other hand is a native Linux file system, 71 00:02:46,257 --> 00:02:48,180 and it's using some older releases 72 00:02:48,180 --> 00:02:51,150 and it's still supported in your current Linux releases. 73 00:02:51,150 --> 00:02:55,470 Ext3 is a more modern version of a native Linux file system. 74 00:02:55,470 --> 00:02:58,260 Ext3 is much faster in recovering data, 75 00:02:58,260 --> 00:03:01,170 and it does a better job of ensuring data integrity 76 00:03:01,170 --> 00:03:05,040 in the case of abrupt system shutdowns than ext2 did. 77 00:03:05,040 --> 00:03:09,000 Another default file system in Linux distributions is ext4, 78 00:03:09,000 --> 00:03:11,280 and this supports really large volumes, 79 00:03:11,280 --> 00:03:13,440 up to one exabytes of data, 80 00:03:13,440 --> 00:03:14,970 and it also supports file sizes 81 00:03:14,970 --> 00:03:18,570 of up to 16 terabytes in one file. 82 00:03:18,570 --> 00:03:22,710 XFS is a 64-bit, high-performance journaling file system 83 00:03:22,710 --> 00:03:24,240 that provides fast recovery 84 00:03:24,240 --> 00:03:27,390 and can handle really large files efficiently as well. 85 00:03:27,390 --> 00:03:31,110 The last type of file system we have is known as BTRFS. 86 00:03:31,110 --> 00:03:34,860 BTRFS is a modern, copy-on-right file system for Linux 87 00:03:34,860 --> 00:03:36,360 that's designed with advanced features 88 00:03:36,360 --> 00:03:38,760 in order to provide fault tolerance, repair, 89 00:03:38,760 --> 00:03:41,490 and easy administration of your file system. 90 00:03:41,490 --> 00:03:45,630 BTRFS supports volumes of up to 16 exabytes in size, 91 00:03:45,630 --> 00:03:48,150 files of up to 16 exabytes in size, 92 00:03:48,150 --> 00:03:49,590 and it supports a maximum 93 00:03:49,590 --> 00:03:52,323 of 18 quintillion files on each volume. 94 00:03:53,160 --> 00:03:56,430 Some file systems function as network protocols as well, 95 00:03:56,430 --> 00:03:59,310 and this enables the sharing of data over a network. 96 00:03:59,310 --> 00:04:01,740 For example, the SMB protocol, 97 00:04:01,740 --> 00:04:03,690 also known as Server Message Block, 98 00:04:03,690 --> 00:04:06,270 is going to allow users to share access to files 99 00:04:06,270 --> 00:04:09,090 and other resources over a local area network 100 00:04:09,090 --> 00:04:10,920 which is known as a LAN. 101 00:04:10,920 --> 00:04:14,700 SMB clients make requests for resources to SMB servers, 102 00:04:14,700 --> 00:04:16,290 and these servers will respond 103 00:04:16,290 --> 00:04:18,930 and provide the appropriate level of access. 104 00:04:18,930 --> 00:04:23,490 In addition to SMB, we also have something known as CIFS. 105 00:04:23,490 --> 00:04:26,457 CIFS is the Common Internet File System 106 00:04:26,457 --> 00:04:28,410 and it's a specific implementation 107 00:04:28,410 --> 00:04:31,290 of SMB that is rarely in use today. 108 00:04:31,290 --> 00:04:33,090 Instead, Microsoft designed it 109 00:04:33,090 --> 00:04:35,670 as a successor to SMB version 1, 110 00:04:35,670 --> 00:04:39,270 but SMB version two and three have long since replaced 111 00:04:39,270 --> 00:04:42,240 version one and CIFS. 112 00:04:42,240 --> 00:04:44,970 However, some Linux distributions will still use 113 00:04:44,970 --> 00:04:47,760 the name CIFS in some of the tools 114 00:04:47,760 --> 00:04:50,400 when they're referring to tools that support SMB, 115 00:04:50,400 --> 00:04:52,860 so it is something you need to be aware of. 116 00:04:52,860 --> 00:04:56,340 Another protocol you need to be aware of is NFS, 117 00:04:56,340 --> 00:04:59,220 NFS stands for the Network File System. 118 00:04:59,220 --> 00:05:03,060 The Network File System offers similar functionality to SMB, 119 00:05:03,060 --> 00:05:07,650 but NFS and SMB are not compatible with each other. 120 00:05:07,650 --> 00:05:09,720 If you're going to be using all Linux clients 121 00:05:09,720 --> 00:05:11,130 and servers in an environment, 122 00:05:11,130 --> 00:05:13,110 then you'll probably want to use NFS 123 00:05:13,110 --> 00:05:15,870 because it actually has some better features than SMB. 124 00:05:15,870 --> 00:05:17,520 But if you're going to use a mixture 125 00:05:17,520 --> 00:05:19,230 of Windows and Linux systems, 126 00:05:19,230 --> 00:05:21,060 you want to rely on SMB 127 00:05:21,060 --> 00:05:24,150 because SMB is the default inside of Windows 128 00:05:24,150 --> 00:05:25,980 and is supported right out the bat, 129 00:05:25,980 --> 00:05:28,983 where NFS is not supported by Windows by default. 130 00:05:29,850 --> 00:05:31,080 Another thing we need to talk about 131 00:05:31,080 --> 00:05:33,120 is something known as an index node, 132 00:05:33,120 --> 00:05:35,821 this is also abbreviate as an Inode. 133 00:05:35,821 --> 00:05:38,430 An index node is an object that stores metadata 134 00:05:38,430 --> 00:05:41,850 about a file or directory on a given file system. 135 00:05:41,850 --> 00:05:44,460 This metadata can include time-based values 136 00:05:44,460 --> 00:05:47,100 like when the file was created and last modified, 137 00:05:47,100 --> 00:05:49,350 it can have permission and ownership information. 138 00:05:49,350 --> 00:05:50,730 It can have the block locations 139 00:05:50,730 --> 00:05:52,860 of the files data on a storage device 140 00:05:52,860 --> 00:05:55,650 and other pieces of miscellaneous information. 141 00:05:55,650 --> 00:05:58,440 In instances where there is an unexpected interruption, 142 00:05:58,440 --> 00:06:01,110 the file system can actually quickly recover itself 143 00:06:01,110 --> 00:06:03,300 through journaling because it records changes 144 00:06:03,300 --> 00:06:04,980 to those files that have not been made 145 00:06:04,980 --> 00:06:08,370 to the file system yet inside of this Inode. 146 00:06:08,370 --> 00:06:10,410 The journaling process involves describing 147 00:06:10,410 --> 00:06:12,900 all the changes that must be made to the drive, 148 00:06:12,900 --> 00:06:14,220 the background processing, 149 00:06:14,220 --> 00:06:16,350 performing pending changes when rebooting, 150 00:06:16,350 --> 00:06:18,990 and discarding incomplete entries. 151 00:06:18,990 --> 00:06:21,060 Another type of file system you need to be aware of 152 00:06:21,060 --> 00:06:24,960 is known as a Virtual File System or VFS. 153 00:06:24,960 --> 00:06:27,240 A Virtual File System is going to be created 154 00:06:27,240 --> 00:06:29,490 as a common software interface that sits 155 00:06:29,490 --> 00:06:32,250 between the kernel and the real file system. 156 00:06:32,250 --> 00:06:34,740 In effect, the VFS is going to translate 157 00:06:34,740 --> 00:06:37,890 a real file systems details over to the kernel. 158 00:06:37,890 --> 00:06:40,560 That way, the file system appears to be identical 159 00:06:40,560 --> 00:06:42,360 to any other file system. 160 00:06:42,360 --> 00:06:44,940 With VFS, you can mount many different types 161 00:06:44,940 --> 00:06:47,550 of file systems on the same Linux installation, 162 00:06:47,550 --> 00:06:49,950 and they're all going to appear uniform to the user 163 00:06:49,950 --> 00:06:52,350 and all the applications on that system. 164 00:06:52,350 --> 00:06:54,180 File system labels are going to be assigned 165 00:06:54,180 --> 00:06:57,810 to those file systems for easy identification by VFS. 166 00:06:57,810 --> 00:07:00,780 These labels may be up to 16 characters long, 167 00:07:00,780 --> 00:07:02,580 and they can be displayed or changed 168 00:07:02,580 --> 00:07:06,210 using the e2label command for ext-based file systems, 169 00:07:06,210 --> 00:07:11,210 and the xfs_admin command for XFS-based file systems. 170 00:07:11,280 --> 00:07:13,140 The first task in managing storage 171 00:07:13,140 --> 00:07:14,820 is to partition a storage device 172 00:07:14,820 --> 00:07:18,000 and format the partition with one of these file systems. 173 00:07:18,000 --> 00:07:19,560 This will make the section of the device 174 00:07:19,560 --> 00:07:21,930 available for reading and writing of the data 175 00:07:21,930 --> 00:07:23,820 once you've formatted it. 176 00:07:23,820 --> 00:07:25,350 When I use the term, partition, 177 00:07:25,350 --> 00:07:28,110 this simply means it's a section of the storage drive 178 00:07:28,110 --> 00:07:30,840 that is logically acting as a separate drive. 179 00:07:30,840 --> 00:07:32,760 It enables you to convert a large drive 180 00:07:32,760 --> 00:07:34,980 into smaller, more manageable chunks 181 00:07:34,980 --> 00:07:37,920 leading to a better organization of your data. 182 00:07:37,920 --> 00:07:40,140 There are three types of partitions you can use 183 00:07:40,140 --> 00:07:42,390 and each one has specific features. 184 00:07:42,390 --> 00:07:43,980 We have primary partitions, 185 00:07:43,980 --> 00:07:47,160 extended partitions, and logical partitions. 186 00:07:47,160 --> 00:07:50,850 Primary partitions contain one file system or logical drive, 187 00:07:50,850 --> 00:07:53,460 and it's sometimes referred to as a volume. 188 00:07:53,460 --> 00:07:55,800 The swap file system and the boot partition 189 00:07:55,800 --> 00:07:58,620 are normally created in the primary partition. 190 00:07:58,620 --> 00:08:01,380 Linux likes to push some of its unused files from RAM 191 00:08:01,380 --> 00:08:04,680 to the swap space to free up actual physical memory, 192 00:08:04,680 --> 00:08:06,990 this goes to what we call the swap space. 193 00:08:06,990 --> 00:08:10,290 This swap space is simply a partition on the storage device 194 00:08:10,290 --> 00:08:12,000 that's going to be used when the system runs out 195 00:08:12,000 --> 00:08:14,700 of physical RAM or physical memory. 196 00:08:14,700 --> 00:08:16,530 An extended partition can contain 197 00:08:16,530 --> 00:08:18,450 several file systems as well, 198 00:08:18,450 --> 00:08:21,180 these are referred to as logical drives. 199 00:08:21,180 --> 00:08:23,910 This partition type does not contain any data, 200 00:08:23,910 --> 00:08:26,280 and it has a separate partition table. 201 00:08:26,280 --> 00:08:29,280 The logical partition is a part of the physical drive 202 00:08:29,280 --> 00:08:30,510 that's been partitioned off 203 00:08:30,510 --> 00:08:32,610 and allocated as an independent unit 204 00:08:32,610 --> 00:08:35,010 and functions as a separate drive. 205 00:08:35,010 --> 00:08:36,210 There's also going to be times 206 00:08:36,210 --> 00:08:38,400 when you need to create a new partition table 207 00:08:38,400 --> 00:08:41,610 or modify existing entries on the partition table, 208 00:08:41,610 --> 00:08:44,820 to do this, you're going to use the fdisk utility. 209 00:08:44,820 --> 00:08:47,370 This is a text-based, menu-driven program 210 00:08:47,370 --> 00:08:49,050 that's used to create, modify, 211 00:08:49,050 --> 00:08:52,200 or delete partitions on a given storage drive. 212 00:08:52,200 --> 00:08:54,180 Fdisk will also enable you to specify 213 00:08:54,180 --> 00:08:56,580 the size of those partitions. 214 00:08:56,580 --> 00:08:59,940 The fdisk utility supports a number of command line options 215 00:08:59,940 --> 00:09:02,430 including things like option -b. 216 00:09:02,430 --> 00:09:05,550 If you use option -b and then the sector size, 217 00:09:05,550 --> 00:09:08,730 you're going to be able to specify the number of drive sectors. 218 00:09:08,730 --> 00:09:11,400 If you use option -H, heads, 219 00:09:11,400 --> 00:09:14,490 this will be used to specify the number of drive heads. 220 00:09:14,490 --> 00:09:17,010 If you use option -S, sectors, 221 00:09:17,010 --> 00:09:18,450 this is going to be used to specify 222 00:09:18,450 --> 00:09:20,430 the number of sectors per track. 223 00:09:20,430 --> 00:09:23,400 If you use option -s, with a lowercase s, 224 00:09:23,400 --> 00:09:25,350 and then the partition, this will be used 225 00:09:25,350 --> 00:09:28,410 to print out the partition size in blocks. 226 00:09:28,410 --> 00:09:30,870 The option -l is going to be used to list 227 00:09:30,870 --> 00:09:33,870 all the partition tables for a given device. 228 00:09:33,870 --> 00:09:36,360 Aside from supplying different command line options, 229 00:09:36,360 --> 00:09:38,220 you can also choose various options 230 00:09:38,220 --> 00:09:40,770 when you're working in the fdisk menu itself 231 00:09:40,770 --> 00:09:45,770 including the options of N, D, P, W, and Q. 232 00:09:46,110 --> 00:09:49,380 Option N is going to be used to create new partitions. 233 00:09:49,380 --> 00:09:50,970 Option D is going to be used 234 00:09:50,970 --> 00:09:53,130 to delete or remove a partition. 235 00:09:53,130 --> 00:09:56,400 Option P is used to list out the existing partitions, 236 00:09:56,400 --> 00:09:58,920 almost like a print-to-screen function. 237 00:09:58,920 --> 00:10:01,650 Option W is going to be used to write the changes 238 00:10:01,650 --> 00:10:04,140 to the drive and exit the utility. 239 00:10:04,140 --> 00:10:07,350 Option Q is going to be used to cancel the changes made 240 00:10:07,350 --> 00:10:09,480 and exit the utility as well. 241 00:10:09,480 --> 00:10:10,980 Now, in addition to fdisk, 242 00:10:10,980 --> 00:10:14,250 there's another utility we can use to manage our partitions, 243 00:10:14,250 --> 00:10:17,697 this is known as the GNU Parted command. 244 00:10:17,697 --> 00:10:20,820 The GNU Parted command is going to be particularly useful 245 00:10:20,820 --> 00:10:23,700 when you're creating partitions on new storage drives. 246 00:10:23,700 --> 00:10:25,350 This tool can be used to create, 247 00:10:25,350 --> 00:10:27,900 destroy, and resize partitions. 248 00:10:27,900 --> 00:10:31,290 The Parted command runs the GNU Parted utility, 249 00:10:31,290 --> 00:10:32,790 and just like fdisk, 250 00:10:32,790 --> 00:10:35,490 Parted includes a menu-driven interactive mode 251 00:10:35,490 --> 00:10:37,590 where you can input various options. 252 00:10:37,590 --> 00:10:39,360 The option, select, is going to be used 253 00:10:39,360 --> 00:10:42,540 to choose which device or partition you want to modify. 254 00:10:42,540 --> 00:10:45,810 The option, mkpart, is going to be used to create a partition 255 00:10:45,810 --> 00:10:49,560 or make a partition with a specific file system type. 256 00:10:49,560 --> 00:10:51,240 Option, print, is going to be used 257 00:10:51,240 --> 00:10:53,910 to list out the partition table to the screen. 258 00:10:53,910 --> 00:10:56,730 Option, resizepart, is going to be used to resize 259 00:10:56,730 --> 00:10:59,910 or modify the end position of a given partition. 260 00:10:59,910 --> 00:11:02,850 Option, rm, is going to be used to delete a partition. 261 00:11:02,850 --> 00:11:04,650 And option, quit, is going to be used 262 00:11:04,650 --> 00:11:07,560 to exit the GNU Parted utility. 263 00:11:07,560 --> 00:11:09,090 After you create a partition, 264 00:11:09,090 --> 00:11:11,550 you can't add a file system to that partition 265 00:11:11,550 --> 00:11:14,790 unless the kernel can read it from the partition table. 266 00:11:14,790 --> 00:11:16,980 So, instead of rebooting the system, 267 00:11:16,980 --> 00:11:19,650 it's better to run the command, partprobe, 268 00:11:19,650 --> 00:11:23,100 after you run fdisk or the Parted command. 269 00:11:23,100 --> 00:11:25,140 If you do this, it makes the kernel aware 270 00:11:25,140 --> 00:11:28,320 of your new partition configurations that you just made. 271 00:11:28,320 --> 00:11:30,150 The partprobe command is going to be used 272 00:11:30,150 --> 00:11:31,920 to update the kernel with the changes 273 00:11:31,920 --> 00:11:34,650 that now exist within the given partition table. 274 00:11:34,650 --> 00:11:36,810 The command first checks the partition table, 275 00:11:36,810 --> 00:11:38,040 and if there's any changes, 276 00:11:38,040 --> 00:11:41,490 it automatically updates the kernel with those changes. 277 00:11:41,490 --> 00:11:43,140 Another important command to know 278 00:11:43,140 --> 00:11:47,970 is the make file system command which is written as mkfs. 279 00:11:47,970 --> 00:11:51,630 The mkfs command is used to build a Linux file system 280 00:11:51,630 --> 00:11:55,650 on a device which is normally going to be a drive partition. 281 00:11:55,650 --> 00:11:57,270 We're going to talk about some of the options 282 00:11:57,270 --> 00:11:59,160 of the mkfs command here, 283 00:11:59,160 --> 00:12:01,110 and give you some of their basic descriptions. 284 00:12:01,110 --> 00:12:04,740 If you want to learn more, you can always type, man mkfs, 285 00:12:04,740 --> 00:12:07,470 at your command prompt and learn more about it. 286 00:12:07,470 --> 00:12:10,560 First, we have option -v, 287 00:12:10,560 --> 00:12:12,810 this is used to produce verbose output 288 00:12:12,810 --> 00:12:14,820 where the output message is going to keep updating 289 00:12:14,820 --> 00:12:17,460 constantly as the program is processing. 290 00:12:17,460 --> 00:12:20,580 If instead you use option -V, 291 00:12:20,580 --> 00:12:22,680 this will produce verbose output as well, 292 00:12:22,680 --> 00:12:25,860 but it'll also include all the file system specific commands 293 00:12:25,860 --> 00:12:27,750 that are being executed. 294 00:12:27,750 --> 00:12:31,470 If you use option -t and the file system type, 295 00:12:31,470 --> 00:12:33,630 you're going to be specifying the type of file system 296 00:12:33,630 --> 00:12:35,760 you want built on this computer. 297 00:12:35,760 --> 00:12:39,630 If you use option, fs -options, it's going to be used to pass 298 00:12:39,630 --> 00:12:43,560 the file system specific options to the file system builder. 299 00:12:43,560 --> 00:12:46,980 If you use option -c, it's going to be used to check the device 300 00:12:46,980 --> 00:12:50,460 for any bad blocks before it builds the file system. 301 00:12:50,460 --> 00:12:53,250 If you use option -l and the file name, 302 00:12:53,250 --> 00:12:54,690 it's going to actually read the list 303 00:12:54,690 --> 00:12:56,940 of bad blocks from a specified file 304 00:12:56,940 --> 00:12:59,220 that you've already run this command against. 305 00:12:59,220 --> 00:13:01,950 So, when it comes down to the make file system command, 306 00:13:01,950 --> 00:13:03,780 there's really two ways to run it. 307 00:13:03,780 --> 00:13:07,770 The first is to type mkfs, set up your options, 308 00:13:07,770 --> 00:13:09,480 and then enter your device name. 309 00:13:09,480 --> 00:13:14,160 The second way is to use mkfs putting your file system type, 310 00:13:14,160 --> 00:13:16,113 your options, and the device name. 311 00:13:17,220 --> 00:13:20,940 Another thing we need to cover is the fstab file. 312 00:13:20,940 --> 00:13:23,850 The fstab file is a configuration file 313 00:13:23,850 --> 00:13:27,120 that stores information about storage devices and partitions 314 00:13:27,120 --> 00:13:30,150 and where and how those partitions should be mounted. 315 00:13:30,150 --> 00:13:34,740 The fstab file is going to be located in the /etc directory. 316 00:13:34,740 --> 00:13:37,620 It's going to be read by the system during the boot up process 317 00:13:37,620 --> 00:13:40,560 and it can be edited only by your root user. 318 00:13:40,560 --> 00:13:43,620 The fstab file consists of a number of lines, 319 00:13:43,620 --> 00:13:46,710 one for each file system that the system knows about. 320 00:13:46,710 --> 00:13:48,360 Each line has six fields 321 00:13:48,360 --> 00:13:51,360 that are going to be separated by spaces or tabs. 322 00:13:51,360 --> 00:13:54,150 The first field is the Device or Partition Name, 323 00:13:54,150 --> 00:13:55,770 and it specifies the name of the device 324 00:13:55,770 --> 00:13:57,900 or file system that you want to mount. 325 00:13:57,900 --> 00:13:59,550 The Default Mount Point indicates 326 00:13:59,550 --> 00:14:01,890 where the file system is going to be mounted, 327 00:14:01,890 --> 00:14:03,480 so it might be, slash, 328 00:14:03,480 --> 00:14:05,970 for the root file system as an example. 329 00:14:05,970 --> 00:14:08,160 The File System Type will also specify 330 00:14:08,160 --> 00:14:11,760 the type of file system used by that device or partition. 331 00:14:11,760 --> 00:14:14,070 The Mount Options field specifies a set 332 00:14:14,070 --> 00:14:16,890 of comma-separated options that will be activated 333 00:14:16,890 --> 00:14:18,990 when the file system is mounted. 334 00:14:18,990 --> 00:14:20,820 The Dump Options field indicates 335 00:14:20,820 --> 00:14:23,970 if the Dump utility should back up the file system. 336 00:14:23,970 --> 00:14:26,910 The fsck Options field will specify the order 337 00:14:26,910 --> 00:14:30,840 in which the fsck utility or the File System Checker utility 338 00:14:30,840 --> 00:14:32,970 should check the file system. 339 00:14:32,970 --> 00:14:34,620 Another file we need to talk about 340 00:14:34,620 --> 00:14:36,810 is located in the /etc directory 341 00:14:36,810 --> 00:14:41,493 and it's known as C-R-Y-P-T-T-A-B, or crypttab. 342 00:14:42,749 --> 00:14:45,330 The /etc/crypttab file performs 343 00:14:45,330 --> 00:14:47,850 a similar function to the fstab file, 344 00:14:47,850 --> 00:14:50,220 but its purpose is to store information 345 00:14:50,220 --> 00:14:52,380 about encrypted devices and partitions 346 00:14:52,380 --> 00:14:55,530 that have to be unlocked and mounted on system boot. 347 00:14:55,530 --> 00:14:58,470 Its format is going to be similar to the fstab file, 348 00:14:58,470 --> 00:15:00,690 but it includes an optional password field 349 00:15:00,690 --> 00:15:03,540 for unlocking encrypted devices. 350 00:15:03,540 --> 00:15:05,910 As we've talked about all these different utilities, 351 00:15:05,910 --> 00:15:07,680 the overall process of setting up 352 00:15:07,680 --> 00:15:10,020 storage devices for use on Linux machines 353 00:15:10,020 --> 00:15:12,960 includes just a few key things you need to do. 354 00:15:12,960 --> 00:15:15,570 First, you need to partition the storage device 355 00:15:15,570 --> 00:15:18,240 using a tool like fdisk or Parted. 356 00:15:18,240 --> 00:15:21,840 Then, you need to format the partition using a file system, 357 00:15:21,840 --> 00:15:23,040 and this will be done using something 358 00:15:23,040 --> 00:15:26,760 like mkfs or the Make File System tool. 359 00:15:26,760 --> 00:15:29,460 Then, you need to add the format of partition 360 00:15:29,460 --> 00:15:31,890 to the fstab file so it can be configured 361 00:15:31,890 --> 00:15:34,320 by the system to run at boot up. 362 00:15:34,320 --> 00:15:37,290 In Linux, everything is going to be treated as a file, 363 00:15:37,290 --> 00:15:41,250 even a directory or an entire disk volume or partition. 364 00:15:41,250 --> 00:15:43,500 When you look at a file system, you're going to see it 365 00:15:43,500 --> 00:15:48,115 written out as a directory known as /dev, for device. 366 00:15:48,115 --> 00:15:50,700 A /dev directory is a special file 367 00:15:50,700 --> 00:15:52,740 that contains details about all the files 368 00:15:52,740 --> 00:15:55,320 and subdirectories that are housed within it. 369 00:15:55,320 --> 00:15:57,030 Linux uses naming conventions 370 00:15:57,030 --> 00:16:00,150 so that storage devices are easily located by the system 371 00:16:00,150 --> 00:16:02,850 whenever they're attached and when the system boots up. 372 00:16:02,850 --> 00:16:05,040 For storage devices, the naming convention 373 00:16:05,040 --> 00:16:07,590 is typically expressed in three parts, 374 00:16:07,590 --> 00:16:09,270 let's take a look at an example. 375 00:16:09,270 --> 00:16:13,680 If I have a device called /dev/sda1, 376 00:16:13,680 --> 00:16:16,560 this actually tells me a lot about this device. 377 00:16:16,560 --> 00:16:19,020 The first part of that, the sd portion, 378 00:16:19,020 --> 00:16:20,583 refers to the specific type of controller 379 00:16:20,583 --> 00:16:22,830 that that device is using. 380 00:16:22,830 --> 00:16:24,720 The second portion, the a, 381 00:16:24,720 --> 00:16:27,120 is going to refer to the first whole drive 382 00:16:27,120 --> 00:16:30,030 because, a, is the first letter of the alphabet. 383 00:16:30,030 --> 00:16:32,400 Then, if we had a second drive, it would be b, 384 00:16:32,400 --> 00:16:35,580 if we had a third drive, it would be c, and so on. 385 00:16:35,580 --> 00:16:37,890 The third part of this is the number one, 386 00:16:37,890 --> 00:16:39,030 and the number one refers 387 00:16:39,030 --> 00:16:41,250 to the first partition on this drive. 388 00:16:41,250 --> 00:16:43,740 If we had two partitions or three partitions, 389 00:16:43,740 --> 00:16:46,080 we would have a two or a three here. 390 00:16:46,080 --> 00:16:50,340 So, when I have something like /dev/sda1, 391 00:16:50,340 --> 00:16:52,890 we know we have the first storage device 392 00:16:52,890 --> 00:16:55,620 and the first partition on that storage device 393 00:16:55,620 --> 00:16:57,603 because it is sda1. 394 00:16:58,620 --> 00:17:00,810 In addition to using this naming convention, 395 00:17:00,810 --> 00:17:03,630 Linux also has several different persistent naming schemes 396 00:17:03,630 --> 00:17:05,640 to help us identify devices. 397 00:17:05,640 --> 00:17:08,190 Controller-based naming can sometimes be problematic 398 00:17:08,190 --> 00:17:11,520 in systems with more than one type of the same controller. 399 00:17:11,520 --> 00:17:15,030 So, instead, we can use a persistent naming scheme 400 00:17:15,030 --> 00:17:17,910 to overcome this and make it more predictable. 401 00:17:17,910 --> 00:17:20,010 If I'm using a persistent naming scheme 402 00:17:20,010 --> 00:17:22,589 that's based on the device's hardware serial number, 403 00:17:22,589 --> 00:17:27,589 I'm going to do this by using /dev/disk/ID number. 404 00:17:28,170 --> 00:17:30,240 If I'm using a persistent naming scheme 405 00:17:30,240 --> 00:17:31,530 that refers to an identifier 406 00:17:31,530 --> 00:17:34,050 based on the shortest physical path to the device, 407 00:17:34,050 --> 00:17:39,050 I might use something like /dev/disk/path. 408 00:17:39,120 --> 00:17:41,880 Finally, if I'm going to use a persistent naming scheme 409 00:17:41,880 --> 00:17:45,660 based on the universally unique identifier, or UUID, 410 00:17:45,660 --> 00:17:50,660 I would write this as /dev/disk/UUID. 411 00:17:50,730 --> 00:17:53,580 And this would refer to that universal unique identifier 412 00:17:53,580 --> 00:17:54,720 that's assigned to the device 413 00:17:54,720 --> 00:17:57,000 when the file system was first created on it. 414 00:17:57,000 --> 00:17:58,380 The last thing we need to discuss 415 00:17:58,380 --> 00:17:59,790 is some special character devices 416 00:17:59,790 --> 00:18:02,280 that exist under the /dev directory. 417 00:18:02,280 --> 00:18:07,280 This includes a /dev/null, /dev/zero, and /dev/urandom. 418 00:18:08,340 --> 00:18:10,200 As I mentioned earlier in this lesson, 419 00:18:10,200 --> 00:18:12,030 everything in Linux is created as a file 420 00:18:12,030 --> 00:18:13,980 and mounted on the file system. 421 00:18:13,980 --> 00:18:15,480 Just like we can mount a hard drive 422 00:18:15,480 --> 00:18:18,630 to the /dev/sda1 directory in the file system 423 00:18:18,630 --> 00:18:20,130 in order to interact with it, 424 00:18:20,130 --> 00:18:23,026 we can also use things like /dev/null, 425 00:18:23,026 --> 00:18:26,340 and /dev/zero, and /dev/urandom 426 00:18:26,340 --> 00:18:28,020 which are special character devices 427 00:18:28,020 --> 00:18:31,050 that are installed by default in most Linux distributions. 428 00:18:31,050 --> 00:18:33,870 And each of these are used for a specific purpose. 429 00:18:33,870 --> 00:18:36,450 The /dev/null special character device 430 00:18:36,450 --> 00:18:38,370 is a special type of virtual device 431 00:18:38,370 --> 00:18:39,870 that allows you to discard anything 432 00:18:39,870 --> 00:18:42,480 that you send to it or redirect into it. 433 00:18:42,480 --> 00:18:45,810 Think of the /dev/null as a big black hole, 434 00:18:45,810 --> 00:18:47,670 and any data streams or character streams 435 00:18:47,670 --> 00:18:50,220 that you don't want to deal with or save to a file, 436 00:18:50,220 --> 00:18:53,460 you can simply redirect those into the /dev/null 437 00:18:53,460 --> 00:18:55,380 and it's going to disappear forever. 438 00:18:55,380 --> 00:18:58,140 If you try to read from the /dev/null device, 439 00:18:58,140 --> 00:19:00,450 you're simply going to receive an End of File message 440 00:19:00,450 --> 00:19:02,700 because you've effectively reached the end of that file 441 00:19:02,700 --> 00:19:06,270 because that file is always empty and contains nothing. 442 00:19:06,270 --> 00:19:08,910 The /dev/zero special character device 443 00:19:08,910 --> 00:19:11,550 is going to be used as a special type of virtual device 444 00:19:11,550 --> 00:19:14,700 that'll return a null character anytime you read from it. 445 00:19:14,700 --> 00:19:17,970 If you redirect the output to the /dev/zero device, 446 00:19:17,970 --> 00:19:19,170 it is going to discard the data 447 00:19:19,170 --> 00:19:21,870 just like the /dev/null device did. 448 00:19:21,870 --> 00:19:23,520 But the big difference is, 449 00:19:23,520 --> 00:19:26,190 when you try to read from /dev/zero, 450 00:19:26,190 --> 00:19:29,550 it's going to act differently than /dev/null did. 451 00:19:29,550 --> 00:19:32,310 You're not going to get that End of File back immediately. 452 00:19:32,310 --> 00:19:34,050 But instead, it's going to send you back 453 00:19:34,050 --> 00:19:39,050 the ASCII null character of the hexadecimal value of 0x00. 454 00:19:39,750 --> 00:19:43,350 Why might you use /dev/zero if all it does is send you back 455 00:19:43,350 --> 00:19:46,260 an endless stream of zeros whenever you read from it? 456 00:19:46,260 --> 00:19:47,910 Well, this is actually useful 457 00:19:47,910 --> 00:19:49,770 when you're trying to sanitize a hard drive 458 00:19:49,770 --> 00:19:52,110 by overriding it with a bunch of zeros. 459 00:19:52,110 --> 00:19:54,870 To do this, you can simply use the dd command 460 00:19:54,870 --> 00:19:56,850 which stands for disk duplicator. 461 00:19:56,850 --> 00:20:01,850 You enter, dd if=/dev/zero of=dev/sda1 bs=1GB count=1024. 462 00:20:12,300 --> 00:20:15,690 And this command will overwrite a one-terabyte hard disk 463 00:20:15,690 --> 00:20:18,810 that is mounted as sda1 with a series of zeros 464 00:20:18,810 --> 00:20:22,650 across the entire drive for the entire one terabyte in size 465 00:20:22,650 --> 00:20:25,890 using block sizes of one gigabyte each. 466 00:20:25,890 --> 00:20:27,150 The next special character device 467 00:20:27,150 --> 00:20:29,163 we need to discuss is the /dev/urandom, 468 00:20:30,882 --> 00:20:34,590 /dev/urandom is a special type of virtual device 469 00:20:34,590 --> 00:20:37,770 that'll return a randomized series of pseudorandom numbers. 470 00:20:37,770 --> 00:20:39,360 For example, if you're creating 471 00:20:39,360 --> 00:20:40,947 a program or a script on a Linux system, 472 00:20:40,947 --> 00:20:43,530 and you want to generate random numbers for something 473 00:20:43,530 --> 00:20:45,480 like determining which side of a rolled dice 474 00:20:45,480 --> 00:20:47,250 would be returned by your program, 475 00:20:47,250 --> 00:20:50,730 you can use /dev/urandom to do that. 476 00:20:50,730 --> 00:20:52,590 For example, let's say I wanted to get 477 00:20:52,590 --> 00:20:54,150 five random characters. 478 00:20:54,150 --> 00:20:59,150 I can enter, head -c5 /dev/urandom, 479 00:20:59,730 --> 00:21:00,960 and then hit Enter. 480 00:21:00,960 --> 00:21:02,850 This will return five random characters 481 00:21:02,850 --> 00:21:07,260 from that special character device called /dev/urandom. 482 00:21:07,260 --> 00:21:09,540 As you can see, there are multiple different ways for us 483 00:21:09,540 --> 00:21:12,690 to reference block and character devices on a Linux system 484 00:21:12,690 --> 00:21:14,440 depending on what your use case is.