When a disk fills up, apps start failing in odd ways: databases stop writing, updates break halfway, and logins can get slow. Small servers fill up faster, so it pays to know where the space goes. Here is how to find out in a few minutes, and what is safe to delete.

About 10 minutes. Debian and Ubuntu commands; the checks work the same on AlmaLinux and Alpine.

1. How full is the disk?

df -h / shows the size of your disk, how much is used and how much is left. On your server the first column shows your own server's name. The Graphs tab in the client area shows the same number. Above about 85% it is time to clean up.

2. Which folders are big?

du adds up folder sizes. Start at the top and work down into the biggest folder:

3. Or browse it with ncdu

ncdu does the same thing with a menu you can move around in with the arrow keys and Enter. Press d on a file to delete it (it asks first) and q to quit.

apt install -y ncdu
ncdu -x /

4. List the biggest files

Usually a few large files are to blame. This lists every file over 100 MB:

Here it is an old backup someone forgot about, and an app log that was never rotated.

5. Clean up safely

• Package cache: apt-get clean removes downloaded package files. Always safe.
• Old kernels and packages: apt autoremove removes packages nothing needs any more. Read the list before you say yes.
• The system journal: journalctl --vacuum-size=50M keeps only the newest 50 MB of logs. See journalctl --disk-usage first.
• A huge log file an app still writes to: empty it with truncate -s 0 FILE rather than deleting it. If you delete a file a running program has open, the space is only freed when that program restarts.
• Old backups: copy them off the server first (see the backups guide), then delete them.

From 37% to 7% used.

Snapshots use disk space too

Snapshots you take in the client area's Snapshots tab are stored on your server's disk, so a snapshot keeps the files it saved, even after you delete them. If space is tight, delete snapshots you no longer need. More in the docs.

Stop it happening again

• Make your app logs rotate: add a file in /etc/logrotate.d/, or log to the journal by running the app as a service (how).
• Cap the journal for good: set SystemMaxUse=100M in /etc/systemd/journald.conf, then systemctl restart systemd-journald.
• Keep backups off the server, not next to the data they protect.

Still short of space? You can move to a bigger plan from the client area at any time. See the plans.

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You start a big download or a backup over SSH, your Wi-Fi drops, and the command dies with your connection. tmux fixes that: it keeps a terminal running on the server, so you can disconnect, go home, and pick it up again later exactly where it was.

About 5 minutes. Works on any natbox plan. Commands for Debian and Ubuntu; on AlmaLinux use dnf install -y tmux, on Alpine apk add tmux.

1. Install tmux and start a session

Log in to your server (ssh root@natbox.io -p YOUR_PORT), install tmux and start a session with a name you will remember:

apt install -y tmux
tmux new -s download

2. Run your long command inside it

You are now inside tmux: it looks like a normal terminal, with a green bar at the bottom showing the session name. Start anything that takes a while. Here we download a 756 MB Debian image:

3. Detach, and log out if you like

Press Ctrl+B, let go, then press D. You are back in your normal shell, and tmux tells you the session is still alive. tmux ls lists your sessions. You can now close the window, log out, or lose your connection: the command keeps running on the server.

4. Come back to it

Log in again, from any computer, and reattach:

tmux attach -t download

Everything is where you left it. Our download had kept going and was at 94%:

When the command has finished, type exit to close the session.

5. Bonus: two panes side by side

Inside tmux, Ctrl+B then % splits the window in two. Here the left pane follows an app's log with journalctl -fu myapp while the right pane checks memory and disk. Ctrl+B then an arrow key moves between panes.

The keys you need

• tmux new -s NAME: start a session. tmux ls: list sessions. tmux attach -t NAME: go back in.
• Ctrl+B then D: detach. Ctrl+B then % or ": split side by side or top and bottom.
• Ctrl+B then [: scroll back with the arrow keys or Page Up; Q to stop scrolling.

tmux or a service?

tmux is for jobs you start by hand and want to watch: downloads, backups, updates, a game server console. Anything that should run all the time and start again after a reboot, such as a bot or a website, belongs in a systemd service instead: see Keep an app running. A tmux session does not survive a server restart.

No server yet? Try one free for a month.

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A lot has changed in the client area over the last few days. Here is everything new, and where to find it.

Manage your servers from Telegram

@NatboxBot lets you check and control your servers from Telegram. Link it from the Telegram page in the client area (account menu, then Telegram). After that you can:

• see each server's status, SSH command, ports, IPv6 address, traffic and paid-until date;
• start, stop and restart a server (stop and restart ask you first);
• pay an unpaid invoice from your account credit, or open it on the website to pay another way;
• get notices for new invoices, payments, support replies, and when a server is set up or a trial is about to end.

The bot also has a small app (the Open app button) with the same features. You can even create an account in the bot. For safety the bot never shows passwords and cannot reinstall a server, and there are no payments inside Telegram.

Snapshots you control

The new Snapshots tab on each server saves the server exactly as it is, for example before a big update, and lets you go back to it later. You can keep 1 snapshot on the free trial and the VPN plan, 2 on Nano, 3 on Box and Box CPU, and 5 on Box Plus. Snapshots use your server's disk space and are stored on the same machine, so keep your own off-site backups as well. The backups guide shows how.

Keep your free trial server

If you like your free trial, you no longer need to start again on a new server. Open the trial in the client area and choose a paid plan to keep it, with all your files and settings. We also email you 7 days and 2 days before a trial ends, so it never ends by surprise.

PayPal from $1

You can now pay with PayPal from $1, so a single month of Nano or Box can be paid directly. Crypto payments start at $3, and account credit works for any amount. The VPN plan and burner servers have their own payment options, listed in the docs.

CaptchaBox: a free captcha for your own sites

CaptchaBox keeps bots out of your website's forms without image puzzles, cookies or Google. Visitors' browsers solve a small puzzle in the background, and your server checks the answer. It is free for 10,000 checks a month, and switching from reCAPTCHA is easy because the server check uses the same answer format. We use it on our own sign-in and sign-up pages.

What's next

Follow this blog for tutorials and news, or subscribe with the RSS feed. You can also watch our videos. Questions or ideas: open a ticket.

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natbox runs small Linux servers with root over SSH, your own block of IPv4 ports and a routed /80 of IPv6, from $1.00 a month. This blog is where we will post step-by-step tutorials, longer guides, and news when something changes on our side.

What you will find here

• Tutorials: one task from start to finish, with every command, written for a natbox server but useful on any Linux VPS.
• Guides: the background to the tutorials, such as how NAT ports and IPv6 work, and how to choose a plan.
• Announcements and updates: new features, changes to plans, and anything that affects your server.

Our reference guides stay in Guides, and the basics of your account are in the docs. Blog posts link to them rather than repeat them.

New: videos

We have also put all our videos on one page: natbox.io/video. They play from our own server, with no YouTube embed and no cookies, and the longer ones have English captions.

• Get a free server and log in over SSH (2:10): start a free trial, log in, change your password, and see how your ports and IPv6 work.
• Host a Discord bot 24/7 (1:39): install a bot, keep its token safe, and run it as a systemd service that restarts by itself.
• Three Shorts of under 35 seconds, including what a NAT VPS is.

Follow along

Add natbox.io/blog/feed.xml to your feed reader, or follow us on X and YouTube. If there is a tutorial you would like to see, open a ticket or email support@natbox.io.

New to natbox? Try a server free for a month.

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