# Linux · Rain Wiki

> Logs, packages, disk space and services on Linux servers and desktops.

- [APT package cache (apt clean and autoclean)](https://raincleaner.eu/wiki/linux/apt-cache-cleanup): Where APT keeps downloaded .deb files, how apt clean, autoclean and autoremove differ, and what is safe to remove on Debian and Ubuntu.
- [cron and crontab](https://raincleaner.eu/wiki/linux/cron): How cron runs scheduled jobs, the five crontab time fields, where system cron files live and how systemd timers compare.
- [df (disk free)](https://raincleaner.eu/wiki/linux/df-disk-free): How to read df output, why Use% can reach 100% before Avail is zero for normal users, and how to check inodes with df -i.
- [Disk usage with du and ncdu](https://raincleaner.eu/wiki/linux/disk-usage-du-ncdu): How to find what fills a Linux disk with du and the interactive ncdu, with options that stay on one file system.
- [Finding large and old files with find](https://raincleaner.eu/wiki/linux/find-large-files): How to use find to list big or old files on Linux, preview them safely and delete only what you checked.
- [Inodes and 'No space left on device'](https://raincleaner.eu/wiki/linux/inodes): What an inode is, how to see inode usage with df -i, and how to find directories with millions of small files.
- [journalctl and the systemd journal](https://raincleaner.eu/wiki/linux/journalctl): How to read logs with journalctl, check how much space the journal uses and shrink it safely with --vacuum options.
- [logrotate](https://raincleaner.eu/wiki/linux/logrotate): What logrotate does, how its configuration in /etc/logrotate.conf and /etc/logrotate.d works, and how to test a rule safely.
- [Swap space on Linux](https://raincleaner.eu/wiki/linux/swap): What swap is, how to see it with free and swapon, how to add a swap file, and what vm.swappiness changes.
- [systemd units and systemctl](https://raincleaner.eu/wiki/linux/systemd-units): What a systemd unit is, the common unit types, and how to start, stop, enable and inspect services with systemctl.