How to add swap file to Azure Linux VM

Login to your VM

Run the following command to edit the config file

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 sudo vi /etc/waagent.conf

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ResourceDisk.Format=y  

ResourceDisk.EnableSwap=y    

ResourceDisk.SwapSizeMB=4000

I set the swap file to 4000M as my vm only 4000M available

use df -h to check avaialbe disk space on the temp drive /dev/sdb1

[bash]

df -h

Filesystem      Size  Used Avail Use% Mounted on

udev            952M     0  952M   0% /dev

tmpfs           193M  1.2M  192M   1% /run

/dev/sda1        29G  3.1G   26G  11% /

tmpfs           964M  992K  963M   1% /dev/shm

tmpfs           5.0M     0  5.0M   0% /run/lock

tmpfs           964M     0  964M   0% /sys/fs/cgroup

/dev/sda15      105M  3.6M  101M   4% /boot/efi

/dev/sdb1       3.9G  3.9G     0 100% /mnt

tmpfs           193M     0  193M   0% /run/user/1000

/dev/loop0       90M   90M     0 100% /snap/core/6818

/dev/loop1       98M   98M     0 100% /snap/docker/372

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Then run free -m to check your new swap file 

[bash]

 free -m

              total        used        free      shared  buff/cache   available

Mem:           1927         930         211           1         786         759

Swap:          3934          16        3917

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use cat /var/log/waagent.log

 to check the log

if you see the following log, means you need to reduce your swap file size as there is no enough space on the temp drive.

[bash]  

2019/05/07 02:10:37.103906 INFO Daemon fallocate unsuccessful, falling back to dd

2019/05/07 02:11:57.305341 INFO Daemon Azure Linux Agent Version:2.2.32.2

2019/05/07 02:11:57.344161 INFO Daemon OS: ubuntu 18.04

2019/05/07 02:11:57.363692 INFO Daemon Python: 3.6.7

2019/05/07 02:11:57.397202 INFO Daemon Add daemon process pid 31642 to walinuxagent systemd cgroup

2019/05/07 02:11:57.425906 INFO Daemon CGroups: ok

2019/05/07 02:11:57.496881 INFO Daemon Run daemon

2019/05/07 02:11:57.507329 INFO Daemon Activate resource disk

2019/05/07 02:11:57.614996 INFO Daemon Resource disk [/dev/sdb1] is already mounted [/mnt]

2019/05/07 02:11:57.642478 WARNING Daemon Failed to write data loss warning:[Errno 1] Operation not permitted: '/mnt/DATALOSS_WARNING_README.txt'

2019/05/07 02:11:57.670093 INFO Daemon Enable swap

2019/05/07 02:11:57.707961 INFO Daemon Remove old swap file

2019/05/07 02:11:58.531786 INFO Daemon Create swap file

2019/05/07 02:11:58.595572 ERROR Daemon Command: [umask 0077 && fallocate -l 4294967296 '/mnt/swapfile'], return code: [1], result: [fallocate: fallocate failed: No space left on device

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