Resize swap space on linux

A few times a year I create a new linux VM. I usually do this by using a kickstart server. The kickstart configuration file I normally use is creating a swap partition which is to small for an Oracle database server. Unfortunately, I forget regularly how to resize the swap partition. Ok, I could update my kickstart configuration file before I create the VM, but this gets forgotten as well 😉


I try to limit the size of my VM as good as possible. Disk space on a SSD disk is not yet as cheep as it should be. Therefore I usually create VM disk which can grow to certain limit. For the swap disk I use a 4GB VM disk and define a swap space of about 2G. The VM disk itself will not grow as long as there is not a lot of swapping. But if the VM has at least 2GB memory the Oracle installer is complaining about to low swap space. Ok, you can ignore this 😉 or you can increase the swap space.

Let’s do it

Check the current settings

cat /etc/fstab
LABEL=/                 /                       ext3    defaults        1 1
LABEL=/u00              /u00                    ext3    defaults        1 2
LABEL=/u01              /u01                    ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-sdb1         swap                    swap    defaults        0 0

Switch off the swap device

swapoff -a

Recreate the swap partition with frisk

fdisk /dev/sdb

Command (m for help): m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Delete the old swap partition

Command (m for help): d
Selected partition 1

Command (m for help): d
No partition is defined yet!

Select the partition type

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

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

Create a new partition. I’ll use the full size of the disk /dev/sdb

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
Partition number (1-4): 1
First cylinder (1-522, default 1):
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-522, default 522):
Using default value 522

Write the changes to disk and exit

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

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

Now it’s time to create a new swap filesystem with mkswap. Because I use labels in fstab, I create the new filesystem again with a label.

mkswap /dev/sdb1 -L SWAP-sdb1

Enable the swap device again

swapon -a

Display the new swap info

swapon -s
Filename                                Type            Size    Used    Priority
/dev/sdb1                               partition       4192924 34324   -1