我的 Dell Optiplex 990 中安装了 32 GB 的 RAM。
lab@lab-445:~/Desktop/M_series_assembly/M4-M5$ free -m
total used free shared buffers cached
Mem: 32058 28989 3068 0 8424 18706
-/+ buffers/cache: 1859 30198
Swap: 30516 0 30516
当我没有运行任何程序时，会怎么样？
以下是请求安装的 32 位应用程序列表：
lab@lab-445:~$ dpkg -l | grep i386
ii gcc-4.6-base:i386 4.6.3-1ubuntu5 GCC, the GNU Compiler Collection (base package)
ii libasn1-8-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - ASN.1 library
ii libasound2:i386 1.0.25-1ubuntu10.2 shared library for ALSA applications
ii libavahi-client3:i386 0.6.30-5ubuntu2.1 Avahi client library
ii libavahi-common-data:i386 0.6.30-5ubuntu2.1 Avahi common data files
ii libavahi-common3:i386 0.6.30-5ubuntu2.1 Avahi common library
ii libc6:i386 2.15-0ubuntu10.7 Embedded GNU C Library: Shared libraries
ii libc6-i386 2.15-0ubuntu10.7 Embedded GNU C Library: 32-bit shared libraries for AMD64
ii libcapi20-3:i386 1:3.12.20071127-0ubuntu11 libraries for CAPI support
ii libcomerr2:i386 1.42-1ubuntu2 common error description library
ii libcroco3:i386 0.6.5-1ubuntu0.1 Cascading Style Sheet (CSS) parsing and manipulation toolkit
ii libcups2:i386 1.5.3-0ubuntu8.5 Common UNIX Printing System(tm) - Core library
ii libdb5.1:i386 5.1.25-11build1 Berkeley v5.1 Database Libraries [runtime]
ii libdbus-1-3:i386 1.4.18-1ubuntu1.7 simple interprocess messaging system (library)
ii libdrm-intel1:i386 2.4.52-1~precise1 Userspace interface to intel-specific kernel DRM services -- runtime
ii libdrm-nouveau1a:i386 2.4.52-1~precise1 Userspace interface to nouveau-specific kernel DRM services -- runtime
ii libdrm-radeon1:i386 2.4.52-1~precise1 Userspace interface to radeon-specific kernel DRM services -- runtime
ii libdrm2:i386 2.4.52-1~precise1 Userspace interface to kernel DRM services -- runtime
ii libexif12:i386 0.6.20-2ubuntu0.1 library to parse EXIF files
ii libexpat1:i386 2.0.1-7.2ubuntu1.1 XML parsing C library - runtime library
ii libffi6:i386 3.0.11~rc1-5 Foreign Function Interface library runtime
ii libfontconfig1:i386 2.8.0-3ubuntu9.1 generic font configuration library - runtime
ii libfreetype6:i386 2.4.8-1ubuntu2.1 FreeType 2 font engine, shared library files
ii libgcc1:i386 1:4.6.3-1ubuntu5 GCC support library
ii libgcrypt11:i386 1.5.0-3ubuntu0.3 LGPL Crypto library - runtime library
ii libgd2-xpm:i386 2.0.36~rc1~dfsg-6ubuntu2 GD Graphics Library version 2
ii libgettextpo0:i386 0.18.1.1-5ubuntu3 GNU Internationalization library
ii libgif4:i386 4.1.6-9ubuntu1 library for GIF images (library)
ii libgl1-mesa-dri:i386 8.0.4-0ubuntu0.7 free implementation of the OpenGL API -- DRI modules
ii libgl1-mesa-glx:i386 8.0.4-0ubuntu0.7 free implementation of the OpenGL API -- GLX runtime
ii libglapi-mesa:i386 8.0.4-0ubuntu0.7 free implementation of the GL API -- shared library
ii libglib2.0-0:i386 2.32.4-0ubuntu1 GLib library of C routines
ii libglu1-mesa:i386 8.0.4-0ubuntu0.7 Mesa OpenGL utility library (GLU)
ii libgnutls26:i386 2.12.14-5ubuntu3.8 GNU TLS library - runtime library
ii libgomp1:i386 4.6.3-1ubuntu5 GCC OpenMP (GOMP) support library
ii libgpg-error0:i386 1.10-2ubuntu1 library for common error values and messages in GnuPG components
ii libgphoto2-2:i386 2.4.13-1ubuntu1.2 gphoto2 digital camera library
ii libgphoto2-port0:i386 2.4.13-1ubuntu1.2 gphoto2 digital camera port library
ii libgpm2:i386 1.20.4-4 General Purpose Mouse - shared library
ii libgssapi-krb5-2:i386 1.10+dfsg~beta1-2ubuntu0.5 MIT Kerberos runtime libraries - krb5 GSS-API Mechanism
ii libgssapi3-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - GSSAPI support library
ii libgstreamer-plugins-base0.10-0:i386 0.10.36-1ubuntu0.1 GStreamer libraries from the "base" set
ii libgstreamer0.10-0:i386 0.10.36-1ubuntu1 Core GStreamer libraries and elements
ii libhcrypto4-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - crypto library
ii libheimbase1-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - Base library
ii libheimntlm0-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - NTLM support library
ii libhx509-5-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - X509 support library
ii libice6:i386 2:1.0.7-2build1 X11 Inter-Client Exchange library
ii libieee1284-3:i386 0.2.11-10build1 cross-platform library for parallel port access
ii libjpeg-turbo8:i386 1.1.90+svn733-0ubuntu4.4 IJG JPEG compliant runtime library.
ii libjpeg8:i386 8c-2ubuntu7 Independent JPEG Group's JPEG runtime library (dependency package)
ii libk5crypto3:i386 1.10+dfsg~beta1-2ubuntu0.5 MIT Kerberos runtime libraries - Crypto Library
ii libkeyutils1:i386 1.5.2-2 Linux Key Management Utilities (library)
ii libkrb5-26-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - libraries
ii libkrb5-3:i386 1.10+dfsg~beta1-2ubuntu0.5 MIT Kerberos runtime libraries
ii libkrb5support0:i386 1.10+dfsg~beta1-2ubuntu0.5 MIT Kerberos runtime libraries - Support library
ii liblcms1:i386 1.19.dfsg-1ubuntu3 Little CMS color management library
ii libldap-2.4-2:i386 2.4.28-1.1ubuntu4.4 OpenLDAP libraries
ii libllvm3.0:i386 3.0-4ubuntu1 Low-Level Virtual Machine (LLVM), runtime library
ii libltdl7:i386 2.4.2-1ubuntu1 A system independent dlopen wrapper for GNU libtool
ii libmpg123-0:i386 1.12.1-3.2ubuntu1 MPEG layer 1/2/3 audio decoder -- runtime library
ii libncurses5:i386 5.9-4 shared libraries for terminal handling
ii libopenal1:i386 1:1.13-4ubuntu3 Software implementation of the OpenAL API (shared library)
ii liborc-0.4-0:i386 1:0.4.16-1ubuntu2 Library of Optimized Inner Loops Runtime Compiler
ii libp11-kit0:i386 0.12-2ubuntu1 Library for loading and coordinating access to PKCS#11 modules - runtime
ii libpciaccess0:i386 0.12.902-1ubuntu0.2 Generic PCI access library for X
ii libpcre3:i386 8.12-4 Perl 5 Compatible Regular Expression Library - runtime files
ii libpng12-0:i386 1.2.46-3ubuntu4 PNG library - runtime
ii libroken18-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - roken support library
ii libsane:i386 1.0.22-7ubuntu1 API library for scanners
ii libsasl2-2:i386 2.1.25.dfsg1-3ubuntu0.1 Cyrus SASL - authentication abstraction library
ii libsasl2-modules:i386 2.1.25.dfsg1-3ubuntu0.1 Cyrus SASL - pluggable authentication modules
ii libselinux1:i386 2.1.0-4.1ubuntu1 SELinux runtime shared libraries
ii libsm6:i386 2:1.2.0-2build1 X11 Session Management library
ii libsqlite3-0:i386 3.7.9-2ubuntu1.1 SQLite 3 shared library
ii libssl1.0.0:i386 1.0.1-4ubuntu5.20 SSL shared libraries
ii libstdc++6:i386 4.6.3-1ubuntu5 GNU Standard C++ Library v3
ii libtasn1-3:i386 2.10-1ubuntu1.2 Manage ASN.1 structures (runtime)
ii libtiff4:i386 3.9.5-2ubuntu1.6 Tag Image File Format (TIFF) library
ii libtinfo5:i386 5.9-4 shared low-level terminfo library for terminal handling
ii libunistring0:i386 0.9.3-5 Unicode string library for C
ii libusb-0.1-4:i386 2:0.1.12-20 userspace USB programming library
ii libuuid1:i386 2.20.1-1ubuntu3.1 Universally Unique ID library
ii libv4l-0:i386 0.8.6-1ubuntu2 Collection of video4linux support libraries
ii libv4lconvert0:i386 0.8.6-1ubuntu2 Video4linux frame format conversion library
ii libwind0-heimdal:i386 1.6~git20120311.dfsg.1-2ubuntu0.1 Heimdal Kerberos - stringprep implementation
ii libx11-6:i386 2:1.4.99.1-0ubuntu2.2 X11 client-side library
ii libx11-xcb1:i386 2:1.4.99.1-0ubuntu2.2 Xlib/XCB interface library
ii libxau6:i386 1:1.0.6-4 X11 authorisation library
ii libxcb-glx0:i386 1.8.1-1ubuntu0.2 X C Binding, glx extension
ii libxcb1:i386 1.8.1-1ubuntu0.2 X C Binding
ii libxcomposite1:i386 1:0.4.3-2build1 X11 Composite extension library
ii libxcursor1:i386 1:1.1.12-1ubuntu0.1 X cursor management library
ii libxdamage1:i386 1:1.1.3-2build1 X11 damaged region extension library
ii libxdmcp6:i386 1:1.1.0-4 X11 Display Manager Control Protocol library
ii libxext6:i386 2:1.3.0-3ubuntu0.1 X11 miscellaneous extension library
ii libxfixes3:i386 1:5.0-4ubuntu4.2 X11 miscellaneous 'fixes' extension library
ii libxi6:i386 2:1.7.1.901-1ubuntu1~precise1 X11 Input extension library
ii libxinerama1:i386 2:1.1.1-3ubuntu0.1 X11 Xinerama extension library
ii libxml2:i386 2.7.8.dfsg-5.1ubuntu4.11 GNOME XML library
ii libxpm4:i386 1:3.5.9-4 X11 pixmap library
ii libxrandr2:i386 2:1.3.2-2ubuntu0.2 X11 RandR extension library
ii libxrender1:i386 1:0.9.6-2ubuntu0.1 X Rendering Extension client library
ii libxslt1.1:i386 1.1.26-8ubuntu1.3 XSLT 1.0 processing library - runtime library
ii libxt6:i386 1:1.1.1-2ubuntu0.1 X11 toolkit intrinsics library
ii libxxf86vm1:i386 1:1.1.1-2ubuntu0.1 X11 XFree86 video mode extension library
ii syslinux-legacy 2:3.63+dfsg-2ubuntu5 Bootloader for Linux/i386 using MS-DOS floppies
ii wine-gecko1.4:i386 1.4.0-0ubuntu2 Microsoft Windows compatibility layer (embedded web browser)
ii wine1.4-i386:i386 1.4-0ubuntu4.1 Microsoft Windows Compatibility Layer (32-bit support)
ii zlib1g:i386 1:1.2.3.4.dfsg-3ubuntu4 compression library - runtime
以及机器信息：
lab@lab-445:~$ uname -a
Linux lab-445 3.2.0-65-generic #99-Ubuntu SMP Fri Jul 4 21:03:29 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
答案1
您的 RAM 已被完全识别，因为它显示的是32058MB 总数。
我猜你会认为虽然没有运行任何程序，但内存已经用完了？事实并非如此，因为你30198的应用程序可以使用 1000 MB 的内存。
其余未显示为“可用内存”（3068MB）的部分用作缓存。这是一项很棒的技术，通过将 Ubuntu 认为您可能很快需要的数据从磁盘缓存到可用 RAM 中，可以大大加快硬盘访问速度。此缓存未显示为“可用”，但可用，因为当您的应用程序需要 RAM 时，内核可以立即删除缓存。
看http://www.linuxatemyram.com/以获得更加直观和易于理解的信息。