Crea un file di swap per il tuo server Linux

[Discourse]

For servers with <= 2GB of RAM, running ./discourse-setup will prompt for and automatically create a 2GB swapfile.

Most cloud virtual machine providers do not set up swapfiles as part of their server provisioning.

In particular, upgrading Discourse produces a lot of memory pressure. With a swap file, rather than randomly terminating processes with an out of memory error, things will slow down instead. Having a swap file is a cheap insurance policy that protects you from many other load related failures.

This can be done at any time from the command line on your server.

Set up a 2GB swap file

We recommend a 2GB swap file for Discourse, unless your server has 4GB or more of memory.

In the shell you have opened to your droplet, do the following:

You will need to be root for much of this, so either be root or sudo -s before running these commands! Don’t forget to exit root afterwards.

1. Create an empty swapfile

    install -o root -g root -m 0600 /dev/null /swapfile
   

2. write out a 2GB file named ‘swapfile’

    dd if=/dev/zero of=/swapfile bs=1k count=2048k
   

3. tell linux this is the swap file:

    mkswap /swapfile
   

4. Activate it

    swapon /swapfile
   

5. Add it to the file system table so its there after reboot:

    echo "/swapfile       swap    swap    auto      0       0" | tee -a /etc/fstab
   

6. Set the swappiness to 10 so its only uses as an emergency buffer

    sysctl -w vm.swappiness=10
    echo vm.swappiness = 10 | tee -a /etc/sysctl.conf
   

The whole thing as a single copy and pastable script:

install -o root -g root -m 0600 /dev/null /swapfile
dd if=/dev/zero of=/swapfile bs=1k count=2048k
mkswap /swapfile
swapon /swapfile
echo "/swapfile       swap    swap    auto      0       0" | tee -a /etc/fstab
sysctl -w vm.swappiness=10
echo vm.swappiness = 10 | tee -a /etc/sysctl.conf

Last edited by @JammyDodger 2022-05-23T18:45:59Z

Check document

Perform check on document:

[nathank (Nathan Kershaw)]

Ho provato a configurare uno swapfile più grande (4 GB invece dei 2 GB predefiniti), ma ho riscontrato questo problema durante l’esecuzione dello script sopra:

rm: cannot remove `swapfile’: Operation not permitted

Per aggirare questo problema, ho dovuto fare prima questo:

1. Riavviare il server (non mi permetteva di eseguire swapoff, presumibilmente a causa dell’uso intensivo dello swapfile)
2. swapoff -a -v

[Ed_S]

@nathank

Ho provato a configurare uno swapfile più grande

Per ragioni simili, eseguo con due swapfile:

# swapon
NAME                       TYPE  SIZE  USED PRIO
/var/local/swap/swapfile.0 file 1024M 44.9M   -3
/var/local/swap/swapfile.1 file 1024M 1024M   -2

[pfaffman (Jay Pfaffman)]

Un secondo file di swap potrebbe essere un modo intelligente per evitare il riavvio. Basta creare un secondo file di swap, abilitarlo e quindi rimuovere il primo.

[NateDhaliwal]

Quindi non avremo bisogno di seguire questa guida per creare il file di swap da 2 GB poiché l’installazione lo fa già se abbiamo meno di 2 GB di memoria?

[Ed_S]

@NateDhaliwal

l’installazione fa già questo

Sì, ma se modifichi la configurazione del tuo server, o forse se esegui una migrazione, potresti dover occupartene da solo. (Allo stesso tempo ci sono due importanti configurazioni del kernel da modificare di cui l’installazione non si occupa - vedi MKJ’s Opinionated Discourse Deployment Configuration