Difficulty:: beginner
Tools:: cron, bash, tar

Problem

Backups that depend on remembering to run them are not backups. The folder that matters is usually one folder, and copying it by hand lasts about a week before it stops happening.

Trigger

Cron, every night at 02:00 local time.

Prerequisites

01A machine that is awake at the scheduled time. A laptop asleep at 02:00 skips the run.
02Enough free space for fourteen compressed copies of the folder.
03tar and cron, both present by default on macOS and Linux.

Steps

01
Save the script as backup-folder.sh and make it executable bash
chmod +x backup-folder.sh. Edit SOURCE and DEST at the top; nothing else needs changing.
02
Run it once by hand and confirm the archive opens tar
tar -tzf ~/Backups/Documents-YYYY-MM-DD.tar.gz lists the contents. If that fails, stop here and fix it before scheduling anything.
03
Add the cron line cron
crontab -e, then: 0 2 * * * $HOME/bin/backup-folder.sh >> $HOME/.backup.log 2>&1
04
Check the log the next morning
tail ~/.backup.log. One line per run, with the path it wrote.

Payload · sh

#!/usr/bin/env bash
# Nightly archive of one folder. Keeps the last 14 days, deletes the rest.
set -euo pipefail

SOURCE="$HOME/Documents"
DEST="$HOME/Backups"
KEEP_DAYS=14

mkdir -p "$DEST"
NAME="$(basename "$SOURCE")"
ARCHIVE="$DEST/$NAME-$(date +%Y-%m-%d).tar.gz"

tar --create --gzip --file "$ARCHIVE" --directory "$(dirname "$SOURCE")" "$NAME"
find "$DEST" -name "$NAME-*.tar.gz" -type f -mtime +"$KEEP_DAYS" -delete

echo "$(date +%Y-%m-%dT%H:%M:%S) wrote $ARCHIVE"

Failure modes

!The disk fills and tar writes a truncated archive. The script does not check free space, so watch the log and the archive sizes.
!The source folder is renamed or moved, tar exits non-zero, and set -e stops the run. Nothing is deleted, but nothing is backed up either.
!The archive sits on the same disk as the source, so one dead drive loses both. Point DEST at an external volume or a synced folder.
!cron runs with a minimal environment. Use absolute paths, and test the way cron will see it: env -i /bin/bash $HOME/bin/backup-folder.sh

JSON-LD · HowTo

{
  "@context": "https://schema.org",
  "@type": "HowTo",
  "name": "Back up one folder every night and keep two weeks",
  "description": "A nightly cron job archives one folder to a dated tar.gz and deletes archives older than fourteen days, so a restore is always a single file away.",
  "url": "https://automationsanonymous.com/automations/back-up-one-folder-every-night",
  "tool": [
    {
      "@type": "HowToTool",
      "name": "cron",
      "url": "https://automationsanonymous.com/tools/cron"
    },
    {
      "@type": "HowToTool",
      "name": "bash",
      "url": "https://automationsanonymous.com/tools/bash"
    },
    {
      "@type": "HowToTool",
      "name": "tar",
      "url": "https://automationsanonymous.com/tools/tar"
    }
  ],
  "step": [
    {
      "@type": "HowToStep",
      "position": 1,
      "name": "Save the script as backup-folder.sh and make it executable",
      "text": "chmod +x backup-folder.sh. Edit SOURCE and DEST at the top; nothing else needs changing.",
      "url": "https://automationsanonymous.com/tools/bash"
    },
    {
      "@type": "HowToStep",
      "position": 2,
      "name": "Run it once by hand and confirm the archive opens",
      "text": "tar -tzf ~/Backups/Documents-YYYY-MM-DD.tar.gz lists the contents. If that fails, stop here and fix it before scheduling anything.",
      "url": "https://automationsanonymous.com/tools/tar"
    },
    {
      "@type": "HowToStep",
      "position": 3,
      "name": "Add the cron line",
      "text": "crontab -e, then: 0 2 * * * $HOME/bin/backup-folder.sh >> $HOME/.backup.log 2>&1",
      "url": "https://automationsanonymous.com/tools/cron"
    },
    {
      "@type": "HowToStep",
      "position": 4,
      "name": "Check the log the next morning",
      "text": "tail ~/.backup.log. One line per run, with the path it wrote."
    }
  ],
  "datePublished": "2026-09-05T16:53:12.891Z"
}