Stoppt die Vorratsdatenspeicherung! Jetzt klicken &handeln! Willst du auch an der Aktion teilnehmen? Hier findest du alle relevanten Infos und Materialien:
Jump to menu and information about this site.


/var/cache/apt/ on tmpfs //at 16:44 //by abe

from the fine-tuning dept.

My ASUS EeePC 701 (4G) “nemo” running Debian Sid has a 4 GB SSD as main disk, which is on the one hand quite full (mostly with software I use, but also local working copies of software I work on) and on the other hand an SSD, so I always try to reduce the amount of write to disk without losing convenience. Similar issues have systems which run off a CF or SD card or maybe even an USB stick.

Since I ordered a 2 GB RAM bar together with the EeePC, I not bound to the 512 MB which it had originally. But on the other hand I seldom needed more than 1 GB of RAM. Usually I needed between 400 MB and 1 GB of RAM. So it’s quite obvious to use tmpfs on as many places as possible.

Making /tmp, /var/run and /var/lock tmpfs were the most obvious directories to mount as tmpfs. Especially /var/run on tmpfs brought up a few bugs a while ago (mostly init.d scripts relying on /var/run/$PACKAGENAME/’s existence), but it’s no hassles to use nowadays. Even in Debian Stable such bugs got fixed.

Next target to explore for was /var/cache. According to the FHS, /var/cache is intended for cached data from applications. […] The application must be able to regenerate or restore the data. So it should be safe to put anything under /var/cache on tmpfs.

One directory in there which gets written quite often and with a lot of data on Debian Unstable is /var/cache/apt and its subdirectories, especially /var/cache/apt/archives. If you update your Sid installation daily, all new or updated .debs will be downloaded to /var/cache/apt first.

So I put /var/cache/apt on tmpfs by putting the following line into /etc/fstab:

tmpfs /var/cache/apt tmpfs defaults,noexec,nosuid,nodev,mode=0755 0 0

But despite FHS stating that anything under /var/cache must be reproducible by the application, apt is puking and refusing to work:

!447 Z31 ?0 L1 root@nemo:pts/0 (-zsh) 16:13:10 [~] # apt-get update
E: Archive directory /var/cache/apt/archives/partial is missing.
!448 Z32 ?100 L1 root@nemo:pts/0 (-zsh) 16:13:17 [~] # 

If you create /var/cache/apt/archives/partial, it will also argue about /var/cache/apt/partial.

Of course the workaround is simple: Just put mkdir -p /var/cache/apt/partial /var/cache/apt/archives/partial in /etc/rc.local.

But nevertheless, this is a bug in apt – which already has been reported by madduck earlier this year (#523920). Unfortunately the APT maintainers have not yet even commented on this FHS violation and therefore also a Debian Policy (Section 9.1.1) violation.

One more thought about /var/cache/apt vs only /var/cache/apt/archives: apt-file also caches its data under /var/cache/apt. So if you want to use apt-file after a reboot and have /var/cache/apt mounted as tmpfs, you have to run apt-file update first and it will download all Contents files (can be dozens of megabytes) and not only the differences to previously downloaded Contents files.

So if you use apt-file a lot, you probably go better with making only /var/cache/apt/archives tmpfs and not whole /var/cache/apt.


Re: /var/cache/apt/ on tmpfs

Posted by: James Vega
Time: Sun, 01 Nov 2009 17:34

As for apt-file, if you run it as a normal user it will create the cache in ~/.cache/apt-file as of 2.1.6 (which is in stable).


Re: /var/cache/apt/ on tmpfs

Posted by: James
Time: Sun, 01 Nov 2009 18:05

debconf stores its answers in /var/cache, which seems wrong to me. Other people think so too, see bug 247134 but no-one's done anything abou ti.


Your Comment

Spam Protection: To post a comment, you'll have to answer the following question: What is 42 minus 19?

URL or E-Mail: [http://... or] (optional)
Title: (optional)
Spam Protection Answer:

Tag Cloud

2CV, aha, Apache, APT, aptitude, ASUS, Automobiles, autossh, Berlin, bijou, Blogging, Blosxom, Blosxom Plugin, Browser, BSD, CDU, Chemnitz, Citroën, CLI, CLT, Conkeror, CSS, CX, deb, Debian, Doofe Parteien, E-Mail, eBay, EeePC, Emacs, Epiphany, Etch, ETH Zürich, Events, Experimental, Firefox, Fläsch, FreeBSD, Freitagstexter, FVWM, Galeon, Gecko, git, GitHub, GNOME, GNU, GNU Coreutils, GNU Screen, Google, GPL, grep, grml, gzip, Hackerfunk, Hacks, Hardware, Heise, HTML,, IRC, irssi, Jabber, JavaShit, Kazehakase, Lenny, Liferea, Linux, LinuxTag, LUGS, Lynx, maol, Meme, Microsoft, Mozilla, Music, mutt, Myon, München, nemo, Nokia, nuggets, Open Source, Opera, packaging, Pentium I, Perl, Planet Debian, Planet Symlink, Quiz, Rant, ratpoison, Religion, RIP, Sarcasm, Sarge, Schweiz, screen, Shell, Sid, Spam, Squeeze, SSH, Stoeckchen, Stöckchen, SuSE, Symlink, Symlink-Artikel, Tagging, Talk, taz, Text Mode, ThinkPad, Ubuntu, USA, USB, UUUCO, UUUT, VCFe, Ventilator, Vintage, Wahlen, Wheezy, Wikipedia, Windows, WML, Woody, WTF, X, Xen, zsh, Zürich, ÖPNV


Mo Tu We Th Fr Sa Su

Tattletale Statistics

Blog postings by posting time
Blog posting times this month


Advanced Search


Recent Postings

0 most recent of 0 postings total shown.

Recent Comments

Hackergotchi of Axel Beckert


This is the blog or weblog of Axel Stefan Beckert (aka abe or XTaran) who thought, he would never start blogging... (He also once thought, that there is no reason to switch to this new ugly Netscape thing because Mosaïc works fine. That was about 1996.) Well, times change...

He was born 1975 at Villingen-Schwenningen, made his Abitur at Schwäbisch Hall, studied Computer Science with minor Biology at University of Saarland at Saarbrücken (Germany) and now lives in Zürich (Switzerland), working at the Network Security Group (NSG) of the Central IT Services (Informatikdienste) at ETH Zurich.

Links to internal pages are orange, links to related pages are blue, links to external resources are green and links to Wikipedia articles, Internet Movie Database (IMDb) entries or similar resources are bordeaux. Times are CET respective CEST (which means GMT +0100 respective +0200).

RSS Feeds

Identity Archipelago

Picture Gallery

Button Futility

Valid XHTML Valid CSS
Valid RSS Any Browser
This content is licensed under a Creative Commons License (SA 3.0 DE). Some rights reserved. Hacker Emblem
Get Mozilla Firefox! Powered by Linux!
Typed with GNU Emacs Listed at Tux Mobil
XFN Friendly Button Maker


People I know personally

Other blogs I like or read

Independent News

Interesting Planets

Web comics I like and read

Stalled Web comics I liked

Blogging Software

Blosxom Plugins I use

Bedside Reading

Just read

  • Bastian Sick: Der Dativ ist dem Genitiv sein Tod (Teile 1-3)
  • Neil Gaiman and Terry Pratchett: Good Omens (borrowed from Ermel)

Currently Reading

  • Douglas R. Hofstadter: Gödel, Escher, Bach
  • Neil Gaiman: Keine Panik (borrowed from Ermel)

Yet to read

  • Neil Stephenson: Cryptonomicon (borrowed from Ermel)

Always a good snack

  • Wolfgang Stoffels: Lokomotivbau und Dampftechnik (borrowed from Ermel)
  • Beverly Cole: Trains — The Early Years (getty images)