🧰 Guide to Increasing /tmp Filesystem Size on cPanel Servers

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(AlmaLinux 9 / CloudLinux 9 Compatible)

📘 Introduction

On AlmaLinux 9 and CloudLinux 9 systems running cPanel, the /tmp filesystem is often mounted as a loopback device (e.g. /dev/loop0) and managed by /scripts/securetmp. By default, it’s 4GB or 5% of /usr, whichever is smaller. This guide explains how to increase that limit safely and permanently.

⚠️ Important Notes

  • Advanced knowledge is required. Proceed with caution.
  • Only applies to servers using the cPanel loopback-based /tmp mount. Confirm with: df -h /tmp ✅ Sample correct output: Filesystem Size Used Avail Use% Mounted on /dev/loop0 4.0G 2.0G 2.0G 50% /tmp ❌ If it says /dev/sdaX or another physical mount, stop here and consult your provider.
  • Not supported on Virtuozzo/OpenVZ containers.
  • Performed and tested on AlmaLinux 9 and CloudLinux 9 (EL9-based) systems using systemd.

🛠️ Procedure

1. Connect to the Server

SSH in as root or access the WHM Terminal.

2. Edit /scripts/securetmp

Open the file in an editor:

nano /scripts/securetmp

3. Change the tmpdsksize Value

Locate and update:

my $tmpdsksize = 10485760;  # 10GB in kilobytes

Now comment out the following logic to prevent it from resetting your value:

# my $five_percent_of_available = ( $available * 0.05 );
#     if ( $five_percent_of_available > $tmpdsksize ) {
#         $tmpdsksize = $five_percent_of_available;
#     }

# my $FOUR_GIG_k = ( 1024 * 1024 * 4 );
#     if ( $tmpdsksize > $FOUR_GIG_k ) {
#         $tmpdsksize = $FOUR_GIG_k;
#     }

Save and exit (Ctrl+O, Enter, Ctrl+X).

4. Identify Active Services Using /tmp

Run:

lsof | grep /tmp | grep -v deleted

5. Disable Monitoring of Key Services (Temporarily)

whmapi1 configureservice service=cpsrvd enabled=1 monitored=0
whmapi1 configureservice service=mysql enabled=1 monitored=0
whmapi1 configureservice service=httpd enabled=1 monitored=0

6. Stop Services

/scripts/restartsrv_cpsrvd --stop
/scripts/restartsrv_mysql --stop
/scripts/restartsrv_httpd --stop

7. Unmount /tmp and /var/tmp

umount -l /tmp
umount -l /var/tmp

8. Backup Old tmpDSK File

mv /usr/tmpDSK /usr/tmpDSK_bak

9. Recreate the /tmp Filesystem

Run:

/scripts/securetmp

This recreates /usr/tmpDSK with the new size and mounts /tmp and /var/tmp securely.

10. Restart Services

/scripts/restartsrv_cpsrvd --start
/scripts/restartsrv_mysql --start
/scripts/restartsrv_httpd --start

11. Re-enable Service Monitoring

whmapi1 configureservice service=cpsrvd enabled=1 monitored=1
whmapi1 configureservice service=mysql enabled=1 monitored=1
whmapi1 configureservice service=httpd enabled=1 monitored=1

✅ Final Checks

  • Verify new /tmp size: df -h /tmp
  • Monitor error logs and service behavior for 15–30 minutes post-change.

📌 Notes for EL9 Environments

  • AlmaLinux 9 and CloudLinux 9 use systemd and XFS or ext4 by default.
  • This method avoids editing fstab or mounting options manually.
  • If your server uses /etc/systemd/system/tmp.mount or has custom mounts, double-check those settings.
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