Trabajando con discos (II)

 Vamos a ver como añadir/ampliar nuestra memoria swap en 400MB. El swap en un tipo de memoria de intercambio que se almacena en disco. Primero crearemos la partición en /dev/sda de 400MB y del tipo 82 Linux Swap.

[root@gamma ~]# fdisk /dev/sda
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x08e3a6bd.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): p

Disk /dev/sda: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x08e3a6bd

   Device Boot      Start         End      Blocks   Id  System

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-130, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-130, default 130): +400MB

Command (m for help): p

Disk /dev/sda: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x08e3a6bd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          50      401593+  83  Linux

Command (m for help): t
Selected partition 1
Hex code (type L to list codes): L

 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris       
 1  FAT12           39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      41  PPC PReP Boot   85  Linux extended  c7  Syrinx        
 5  Extended        42  SFS             86  NTFS volume set da  Non-FS data   
 6  FAT16           4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS       4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility  
 8  AIX             4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt        
 9  AIX bootable    50  OnTrack DM      93  Amoeba          e1  DOS access    
 a  OS/2 Boot Manag 51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O       
 b  W95 FAT32       52  CP/M            9f  BSD/OS          e4  SpeedStor     
 c  W95 FAT32 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs       
 e  W95 FAT16 (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  GPT           
 f  W95 Ext'd (LBA) 55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor     
12  Compaq diagnost 61  SpeedStor       a9  NetBSD          f4  SpeedStor     
14  Hidden FAT16 <3 63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary 
16  Hidden FAT16    64  Novell Netware  af  HFS / HFS+      fb  VMware VMFS   
17  Hidden HPFS/NTF 65  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
18  AST SmartSleep  70  DiskSecure Mult b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 75  PC/IX           bb  Boot Wizard hid fe  LANstep       
1c  Hidden W95 FAT3 80  Old Minix       be  Solaris boot    ff  BBT           
1e  Hidden W95 FAT1
Hex code (type L to list codes): 82
Changed system type of partition 1 to 82 (Linux swap / Solaris)

Command (m for help): p

Disk /dev/sda: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x08e3a6bd

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          50      401593+  82  Linux swap / Solaris

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Haremos que el kernel refresque el estado de los discos:

 [root@gamma ~]#partx

Formateamos la partición de swap:

[root@gamma ~]# mkswap /dev/sda1
Setting up swapspace version 1, size = 401588 KiB
no label, UUID=a74e9042-da78-4d6b-afcb-91a71d92c78e

Activamos la partición de swap:

[root@gamma ~]# swapon /dev/sda1

Comprobamos que ahora tenemos +400M más de swap:

[root@gamma ~]# free -l
             total       used       free     shared    buffers     cached
Mem:        760752     471884     288868          0      21724     203588
Low:        760752     471884     288868
High:            0          0          0
-/+ buffers/cache:     246572     514180
Swap:      1425576          0    1425576

Añadir la entrada de /etc/fstab para activar la partición de swap en el arranque.

UUID=a74e9042-da78-4d6b-afcb-91a71d92c78e swap                    swap    defaults        0 0

...(Continuará)