AI agents consume all your memory in linux by default

My 64 GB Linux workstation kept freezing while coding agents worked on a couple of projects. All 4 GB of swap filled up. Applications were killed. Half the memory looked like cache.

Then I found 22 GB of agent-created files in a tmpfs-backed /tmp.

tmpfs stores file contents in RAM or swap. Unlike clean disk-backed cache, those contents cannot simply be discarded. Some memory monitors include tmpfs in cache-related accounting, making the memory pressure easy to misread.¹

Memory-backed temporary storage can offer fast I/O, fewer storage writes, and cleanup on reboot. But swapping can undermine those benefits.²

The distinction is workload size. Systemd recommends /tmp for small, bounded files and /var/tmp for larger data.³ This is not uniquely an AI problem: GCC also creates temporary intermediate files.⁴ Parallel agent work simply made the trade-off visible on my machine.

Run these in a Linux terminal:

findmnt -T /tmp -o TARGET,SOURCE,FSTYPE

df -hT /tmp

sudo du -x -h --max-depth=1 /tmp | sort -h

free -h

Look for tmpfs under FSTYPE. Keep -T: plain findmnt /tmp can return nothing when /tmp is not a separate mount.⁵

df measures the containing filesystem; du measures the directory tree.⁶⁷ In free, focus on available.⁸ Large tmpfs usage alongside low available memory deserves investigation—not automatic blame for every crash.

Create a private directory and check its filesystem and free space:

mkdir -p "$HOME/.local/tmp"
chmod 700 "$HOME/.local/tmp"
findmnt -T "$HOME/.local/tmp" -o TARGET,SOURCE,FSTYPE
df -hT "$HOME/.local/tmp"

mkdir -p creates missing directories; chmod 700 restricts ordinary access to the owner.⁹¹⁰ Confirm the directory is disk-backed before proceeding.

export TMPDIR="$HOME/.local/tmp"

Launch your agent from that same terminal. Programs honoring TMPDIR can use the new location. Hard-coded /tmp paths and existing workspaces need separate changes.³

Verify the path and filesystem inside the agent’s actual execution environment, especially with containers or sandboxes.⁵ Clean up completed scratch data yourself; this directory does not inherit /tmp’s cleanup policy.³

/tmp disk-backed system-wide For systemd-based distributions, inspect first:

systemctl cat tmp.mount --no-pager

findmnt --fstab --mountpoint /tmp

findmnt -T / -o TARGET,SOURCE,FSTYPE,OPTIONS
df -hT /

tmp.mount is one name, with a dot.¹¹

Use the following only when /tmp is tmpfs, its unit is distribution-provided with no local customizations, /etc/fstab has no /tmp entry, and / is writable, disk-backed, and has adequate space. Otherwise, use Option 1 rather than forcing this shortcut.⁵¹¹

sudo systemctl mask tmp.mount

This prevents future activation without unmounting the current /tmp.¹¹ Save your work, copy anything needed out of /tmp, then reboot when ready. Existing tmpfs files disappear; they do not migrate to disk.¹

After reboot, verify:

findmnt -T /tmp -o TARGET,SOURCE,FSTYPE

/tmp should now belong to the disk-backed root filesystem. To reverse the mask, run sudo systemctl unmask tmp.mount, then reboot.¹¹

This trades memory-backed storage for root-disk usage and can remove mount-specific restrictions such as nosuid,nodev. Disk space, cleanup, and security policy still matter.¹²³

Native macOS and Windows normally use disk-backed temporary directories, so large temporary trees primarily consume disk space.¹³¹⁴ They can still exhaust memory; disk-backed does not mean cache-free.¹⁵ For Linux containers or virtual machines, check inside that environment.⁵

This is not a reason to disable tmpfs everywhere. It is a reason to put multi-gigabyte workspaces on storage chosen deliberately.

“Temporary” describes how long data is needed—not where it belongs.

Linux kernel: Tmpfs. ↩

Ubuntu: Data Driven Analysis — /tmp on tmpfs. ↩

systemd: Using /tmp/ and /var/tmp/ Safely. ↩

GCC: Environment Variables. ↩

findmnt(8). ↩

df(1). ↩

du(1). ↩

free(1). ↩

mkdir(1). ↩

chmod(1). ↩

systemctl(1). ↩

systemd: upstream tmp.mount. ↩

Apple: File System Basics. ↩

Microsoft: GetTempPath2. ↩

Microsoft: File Caching. ↩