Written 30 Aug 2026. This is a how-to, not a product card.

See how big one folder is

After SSH works, check how big one folder is with du so you know before you copy or delete. You don't need a file manager for this.

See folders as a tree showed nested folders. Unpack a zip you already have unpacked a zip. Pack files into one archive packed a folder. See what's in a folder listed names. Tonight you check size: how big one folder you already know is. After you unpack a zip, nested folders are hard to size by eye. du tells you how big one folder is. You are still only looking on the computer. It does not need a file manager, a desktop, or a NAS for this one job.

Skip until SSH already works

SSH from the couch should already get you a prompt. If you need nested folders as a drawing, that is see folders as a tree. If you need how much room the whole disk still has, that is see if the computer still has room. If you need which folders eat the disk, that is see which folders are eating the disk. Skip this whole note if you only need a house share other computers browse. That is a folder the house can open. Skip if you need a USB copy of the house folder. That is a backup of the house folder.

What this is

du means disk usage for a path you name. You type du, then a folder in home. Tonight: du -sh ~/some-folder. -s means summary: one number for the whole folder, not a line per nested path. -h means human sizes, like 12K or 4.0M, instead of raw bytes. It is not how full the whole disk is. That is see if the computer still has room (df). It is not ranking every big folder on the computer. That is see which folders are eating the disk. It is not one file's size, date, and permissions. That is see file size, date, and permissions. It is not a nested drawing. That is see folders as a tree. It is not a name list. That is see what's in a folder. It is not a search by name. That is find a file by name. It is not a delete. That is delete a file carefully.

Size a practice folder in home

SSH in. Make sure home is where you sit:

pwd

You want a path that ends in your login name. If not:

cd ~

If you still have ~/tree-me from see folders as a tree, you can size that folder. Otherwise make a tiny practice tree in home only:

mkdir -p ~/size-me/a/b

echo hi > ~/size-me/a/b/hi.txt

Ask how big the whole folder is:

du -sh ~/size-me

Or, if you kept the tree practice folder:

du -sh ~/tree-me

You want one small human size, often a few kilobytes. A nearly empty folder still takes a little room because the computer stores the folder itself.

Optional: see each child sitting right under that folder, without listing every nested file:

du -h -d 1 ~/size-me

-d 1 means one level deep. You get the folder you named, plus each child under it. Files further down are rolled into those children.

Skip du /, du /etc, and sudo du of the whole disk for this practice. Whole-disk room left is see if the computer still has room. Ranking the biggest folders is see which folders are eating the disk.

If du says No such file or directory, you are not in home or the practice folder is missing. pwd, then cd ~, then try again.

When you are done practicing, throw away the practice files. Careful delete only. That is delete a file carefully:

rm -i ~/size-me/a/b/hi.txt

Delete practice folders the same careful way after they are empty. Skip rm -rf.

Useful extras, still home only

Want a size for each item sitting right in that folder?

du -sh ~/size-me/*

That is still a summary per child, not a dump of every file.

Skip du -a as tonight's lesson. That flag lists every file. Tonight: one folder you already know.

Skip other disks, USB sticks, and /srv as tonight's lesson. Practice only in home.

If it says command not found for du, install coreutils, then try again:

sudo apt install coreutils

Debian and Ubuntu Server usually already have it. That install is not a reason to buy a disk-space app.

What this is not

This is not how full the whole disk is. That is see if the computer still has room. It is not ranking every big folder on the computer. That is see which folders are eating the disk. It is not one file's size, date, and permissions. That is see file size, date, and permissions. It is not a nested drawing. That is see folders as a tree. It is not a name list. That is see what's in a folder. It is not a search by name. That is find a file by name. It is not a careful delete. That is delete a file carefully. It is not a USB backup. That is a backup of the house folder. It is not a house share other computers browse. That is a folder the house can open. It is not opening SSH to the internet so you can size folders from a coffee shop. That is keep the computer on the house network. Don't forward port 22.

What next

Need a zip a laptop can open? Pack files into a zip a laptop can open. Need size (or clock) to update by itself? See change without typing again. Need nested folders as a drawing? See folders as a tree. Need how much room the whole disk still has? See if the computer still has room. Need which folders eat the disk? See which folders are eating the disk. Need the throwaway gone for real? Delete a file carefully. Keep SSH on the house network: keep the computer on the house network. Don't forward port 22.

Skip

• Skip if SSH still fails. Finish SSH from the couch first.
• Skip paths under /etc, SSH folders, or paths you don't own. Practice only in home.
• Skip du /, du /etc, and sudo du of the whole disk for this practice. Whole-disk room is see if the computer still has room. Ranking biggest folders is see which folders are eating the disk.
• Skip du -a as tonight's lesson. That dumps every file.
• Skip rm -rf. Careful delete only: delete a file carefully.
• Skip buying a disk-space app. Debian and Ubuntu already ship du.
• Skip opening SSH to the internet so you can size folders from a coffee shop. That is keep the computer on the house network. Don't forward port 22.
• Skip if you actually need the USB backup. That is a backup of the house folder.
• Skip if you only need a house share other computers browse. That is a folder the house can open.