Servers: Ubuntu Swap
Written by Rich Banks on 8th Mar, 2016
I recently had a problem where my Laravel Simple Backup task was being killed by Ubuntu due to a "Cannot Allocate Memory" issue. Composer was also running extremely slowly and sometimes showing a 'proc_open(): fork failed - Cannot allocate memory' error.
After a little Googling, I found that a simple fix would be to enable swap space on the server. I am running an Amazon t2.micro EC2 instance which only has 1GB of RAM so for me 1GB swap space should be sufficient. You may find you would like to have a larger swap file.
Firstly you should check if your system already has any configured swap.
free -mThe output shoule be similar to below. If you do not have swap configured 'Sawp:' should show 0 0 0 like below.
total used free shared buffers cached
Mem: 992 921 71 44 3 130
-/+ buffers/cache: 787 205
Swap: 0 0 0
It is now a good idea to check that you have enough hard disk space for you swap file.
df -h
Filesystem Size Used Avail Use% Mounted on
/dev/xvda1 7.8G 2.0G 5.5G 27% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
udev 492M 8.0K 492M 1% /dev
tmpfs 100M 344K 99M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 497M 0 497M 0% /run/shm
none 100M 0 100M 0% /run/user
If you are happy you have enough space for your swap file you can create the file and enable it.
/bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=1024/sbin/mkswap /var/swap.1/sbin/swapon /var/swap.1If you encounter any errors when running the above commands, try running them as sudo. You can change the size of the swap file by editing 'bs=' and 'count='
Swap should now be enabled. You can check by running.
free -m
total used free shared buffers cached
Mem: 992 905 86 44 3 114
-/+ buffers/cache: 787 205
Swap: 1023 0 1023
This has worked well for me on Ubuntu 14.04.2.
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