Labthrift Labthrift What to buy. What to skip. Why.

Written 29 Aug 2026. This is a how-to, not a product card.

Make a file runnable

After SSH works, change file permissions with chmod so a practice script can run. You don't need a permissions GUI for this.

Put a short line into a file parks words on disk. See what's in a folder can show the permission letters. Tonight you only need those letters to mean “this file may run.” chmod changes who can read, write, or run a file. You are still only practicing in home. The computer does not need a desktop, a permissions GUI, or a NAS for this one job.

Skip until SSH already works

SSH from the couch should already get you a prompt. If you only need a short line on disk, that is put a short line into a file. If you only need the names and sizes, that is see what's in a folder. Skip this whole note if you only need a house share other computers browse. That is a folder the house can open.

What this is

chmod means change mode. It changes the permission bits on a file you own. You run it on the computer, after SSH. It does not write the file's words. That is echo or nano. It does not change who owns the file. That owner job is a different tool, and you don't need it tonight. It does not open a permissions window. One short command, same computer, the run bit flipped on or off.

When ls -l prints a line, the first column looks like -rw-rw-r--. Those letters are read, write, and execute for you, for your group, and for everyone else. An x in that column means “may run.” A dash where the x would be means “may not.” That is the whole first-night story.

Make a practice script runnable

SSH in. Put one short practice script in home. A short name with no spaces is easier to type later:

echo '#!/bin/sh' > ~/hello.sh

echo 'echo hello from the computer' >> ~/hello.sh

The first line tells the computer this file is a shell script. The second line is the one short job. Peek:

cat ~/hello.sh

See the permission letters before you change them:

ls -l ~/hello.sh

You will usually see something like -rw-rw-r-- and no x. Trying to run it as a program fails until you flip that bit:

chmod +x ~/hello.sh

ls -l ~/hello.sh

You want an x in the first group of letters now, often -rwxrwxr-x or similar. Then run it by path:

~/hello.sh

You should see hello from the computer. That is the whole first-night trick.

Useful extras, still practicing only

Need the run bit off again after you practice?

chmod -x ~/hello.sh

ls -l ~/hello.sh

The x should be gone. The words inside the file are still there.

Need a private note that only you can read? Practice on a throwaway file, not on SSH settings:

echo 'practice secret' > ~/private.txt

chmod 600 ~/private.txt

ls -l ~/private.txt

You want something like -rw-------. The number 600 is a short form: you may read and write, nobody else may. Skip deeper number puzzles tonight. chmod +x and chmod 600 are enough for tonight.

If you see command not found, install the usual tools, then try again:

sudo apt install coreutils

Debian and Ubuntu Server usually already have it. That install is not a reason to buy a permissions GUI.

When you are done practicing:

rm -i ~/hello.sh ~/private.txt

What this is not

This is not writing the words inside the file. That is put a short line into a file or edit a file from the couch. It is not listing names. That is see what's in a folder. It is not changing who owns the file. Skip owner changes tonight. It is not turning off password login. That is turn off password login once the key works. It is not a house share other computers browse. That is a folder the house can open.

What next

Need a short line before the script exists? Put a short line into a file. Need several lines in the editor? Edit a file from the couch. Need the names and letters again? See what's in a folder. Need a second name that still points at the same file? Make a shortcut. Need a folder for scripts to land in? Make a folder. Need a file from the laptop instead? Copy a file to the computer from your laptop. When a house job broke, look at the computer's own diary: when something broke, look at the log. When key login is boring on every computer you use, turn off password login once the key works. Keep SSH on the house network: keep the computer on the house network. Don't forward port 22.

Skip

Sources

Debian: chmod. Ubuntu: chmod. GNU coreutils: chmod. Official pages only. For the login, see SSH from the couch. For a short line, see put a short line into a file. For listing letters, see see what's in a folder. For the editor, see edit a file from the couch.

Also on this topic

SSH from the couchType commands on the computer from your laptop, on the house network. Password login first. Don't open this to the internet. Put a short line into a fileAfter SSH works, put one short line into a file with echo so you don't need to open nano. You don't need a file manager app for this. See what's in a folderAfter SSH works, list the folder you are sitting in with ls. You don't need a file manager app for this. Edit a file from the couchAfter SSH works, open a file with nano, change a line, and save. The keys at the bottom of the screen are the whole trick. You don't need a new editor. Make a folderAfter SSH works, make a folder with mkdir so copies and edits have a place to land. You don't need a NAS for this. Make an empty fileAfter SSH works, make an empty file with touch so nano and copies have a file to land on. You don't need a file manager app for this. Delete a file carefullyAfter SSH works, delete one file with rm -i. Ask first. Skip rm -rf. You don't need a NAS for this. Turn off password login once the key worksAfter the laptop key login is boring, tell SSH to stop accepting the password. The key is how you get in. A keyboard on the computer is the backup now.