How do you add swap to an EC2 instance

Question

I m currently running an ec2 micro instance and i ve been finding that the instance occasionally runs out of memory   Other than using a larger instance size  what else can be done

User · Answer

After applying the steps mentioned by ajtrichards you can check if your amazon free tier instance is using swap using this command

cat /proc/meminfo

result:

ubuntu@ip-172-31-24-245:/$ cat /proc/meminfo
MemTotal:         604340 kB
MemFree:            8524 kB
Buffers:            3380 kB
Cached:           398316 kB
SwapCached:            0 kB
Active:           165476 kB
Inactive:         384556 kB
Active(anon):     141344 kB
Inactive(anon):     7248 kB
Active(file):      24132 kB
Inactive(file):   377308 kB
Unevictable:           0 kB
Mlocked:               0 kB

SwapTotal: 1048572 kB

SwapFree: 1048572 kB

Dirty:                 0 kB
Writeback:             0 kB
AnonPages:        148368 kB
Mapped:            14304 kB
Shmem:               256 kB
Slab:              26392 kB
SReclaimable:      18648 kB
SUnreclaim:         7744 kB
KernelStack:         736 kB
PageTables:         5060 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     1350740 kB
Committed_AS:     623908 kB
VmallocTotal:   34359738367 kB
VmallocUsed:        7420 kB
VmallocChunk:   34359728748 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      637952 kB
DirectMap2M:           0 kB

User · Answer

You can create swap space using the following steps Here we are creating swap at  home    dd if  dev zero of  home swapfile1 bs 1024 count 8388608 Here count is kilobyte count of swap space mkswap  home swapfile1 vi  etc fstab make entry    home swapfile1 swap swap defaults 0 0 run  swapon -a

User · Answer

If you are on t2 instances  t2 micro  t2 medium  t2 small   there is no ephemeral or instance storage available to you  So you need to just create your swap in EBS which depending on your use case may or maynot be a good idea  Otherwise follow  David  s answer  and create your swap on the ephemeral storage to avoid paying EBS costs    More info  http   docs aws amazon com AWSEC2 latest UserGuide InstanceStorage html there is a table that shows how much ephemeral storage you get for each instance type

User · Answer

Try swapspace http   pqxx org development swapspace   Most distros have it packaged   On EC2 you might want to change  swappath  to  mnt or high-iops disk

User · Answer

You can use the following script to add swap on Amazon Linux   https   github com chetankapoor swap  Download the script using wget   wget https   raw githubusercontent com chetankapoor swap master swap sh -O swap sh   Then run the script with the following format   sh swap sh 2G   For a complete tutorial you can visit   https   installvirtual com shell-script-to-create-swap

User · Answer

You can add a 1 GB swap to your instance with these commands   sudo dd if  dev zero of  swapfile bs 1M count 1024 sudo mkswap  swapfile sudo swapon  swapfile   To enable it by default after reboot  add this line to  etc fstab    swapfile swap swap defaults 0 0

User · Answer

A fix for this problem is to add swap  i e  paging  space to the instance   Paging works by creating an area on your hard drive and using it for extra memory  this memory is much slower than normal memory however much more of it is available   To add this extra space to your instance you type   sudo  bin dd if  dev zero of  var swap 1 bs 1M count 1024 sudo  sbin mkswap  var swap 1 sudo chmod 600  var swap 1 sudo  sbin swapon  var swap 1   If you need more than 1024 then change that to something higher   To enable it by default after reboot  add this line to  etc fstab    var swap 1   swap    swap    defaults        0   0

User · Answer

Using David s Instance Storage answer initially worked for me  on a m5d 2xlarge  however  after stopping the EC2 instance and turning it back on  I was unable to ssh in to the instance again    The instance logs reported   You are in emergency mode  After logging in  type  journalctl -xb  to view system logs   systemctl reboot  to reboot   systemctl default  or  exit  to boot into default mode  Press Enter for maintenance   I instead followed the AWS instructions in this link and everything worked perfectly  including after turning the instance off and on again   https   aws amazon com premiumsupport knowledge-center ec2-memory-swap-file   sudo dd if  dev zero of  swapfile bs 1G count 4  sudo chmod 600  swapfile  sudo mkswap  swapfile  sudo swapon  swapfile  sudo swapon -s  sudo vi  etc fstab  swapfile swap swap defaults 0 0

User · Answer

Swap should take place on the Instance Storage  ephemeral  disk and not an EBS device  Swapping will cause a lot of IO and will increase cost on EBS  EBS is also slower than the Instance Store and the Instance Store comes free with certain types of EC2 Instances   It will usually be mounted to  mnt but if not run  sudo mount  dev xvda2  mnt   To then create a swap file on this device do the following for a 4GB swapfile  sudo dd if  dev zero of  mnt swapfile bs 1M count 4096   Make sure no other user can view the swap file  sudo chown root root  mnt swapfile sudo chmod 600  mnt swapfile   Make and Flag as swap  sudo mkswap  mnt swapfile sudo swapon  mnt swapfile   Add Make sure the following are in your  etc fstab   dev xvda2       mnt    auto    defaults nobootwait comment cloudconfig 0   2  mnt swapfile swap swap defaults 0 0   lastly enable swap  sudo swapon -a

User · Answer

We can add swap space in any server  create a file using dd command     dd if  dev zero of  swapfile bs 1M count 2048                     or   dd if  dev zero of  swapfile bs 1024M count 2   bs is blocksize and count refers to the size in MB or GB     we can use vice versa   After creation change the permission of file      chmod 600  swapfile    Then makeswap the file      mkswap  swapfile    Then enable the swap file with swapon command      swapon   swapfile    Check with free command whether swap is enabled or not      free -h   swapon -s

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