Centos – Meaning of “available” field in “free -m” command

centoslinux

I am using Linux CentOS 7.2 version.

I have searched details about this but can't found any useful information.

What is this about?

Best Answer

From free(1):

Estimation of how much memory is available for starting new applications, without swapping. Unlike the data provided by the cache or free fields, this field takes into account page cache and also that not all reclaimable memory slabs will be reclaimed due to items being in use (MemAvailable in /proc/meminfo, available on kernels 3.14, emulated on kernels 2.6.27+, otherwise the same as free)

It reports the amount of physical memory that's available, i.e. that can be used without causing the system to start swapping. How can I get the amount of available memory portably across distributions? has more information.

Related Solutions

Bash – is there a “xdotool” rpm available for Centos Linux

Looking closer into it. It looks like xdotool is provided by the nux dextop repository:

[root@nctirlwb07 ~]# yum info xdotool
Loaded plugins: product-id, rhnplugin, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
This system is receiving updates from RHN Classic or RHN Satellite.
Available Packages
Name        : xdotool
Arch        : x86_64
Epoch       : 1
Version     : 2.20110530.1
Release     : 4.el6.nux
Size        : 44 k
Repo        : nux-dextop
Summary     : Fake keyboard/mouse input
URL         : http://www.semicomplete.com/projects/xdotool/
License     : BSD
Description : This tool lets you programmatically (or manually) simulate
            : keyboard input and mouse activity, move and re-size windows, etc.

Centos – How to update OpenSSL on centos 7.2

First, let me say that garethTheRed and Bratchley are right in that the package of OpenSSL you're trying to install is not supported on CentOS, and doing so is not recommended. Trying to do this could cause problems on your system.

If you absolutely must have this installed... As I understand it, you're trying to install nginx-ct, which requires OpenSSL 1.0.2 or higher because of its need for SSL_CTX_add_server_custom_ext and SSL_CTX_set_signed_cert_timestamp_list.

Using yum

Using packages from other unsupported repos for your system is a bad idea, as pointed out by others. From the looks of your yum output, it's complaining about a dependency on the crypto-policies package (required by openssl-libs-1.0.2d-2). You could try to install the crypto-policies package (also from the Fedora 23 repo) first.

Compiling from source

As Bratchley pointed out in this comment, you can try to compile nginx with a specific version of OpenSSL from source. Here are the updated starting commands from that tutorial:

# Install dependencies
sudo yum install unzip gcc pcre-devel zlib-devel make golang

# Grab needed files, correct as of 2016-04-08
wget https://www.openssl.org/source/openssl-1.0.2g.tar.gz
wget http://nginx.org/download/nginx-1.9.14.tar.gz
wget -O nginx-ct.zip https://github.com/grahamedgecombe/nginx-ct/archive/master.zip
tar zxf openssl-1.0.2g.tar.gz
tar zxf nginx-1.9.14.tar.gz
unzip nginx-ct.zip

# Build nginx with openssl 1.0.2 and CT module
cd nginx-1.9.14/
./configure --with-http_ssl_module \
    --with-openssl=`realpath ../openssl-1.0.2g` \
    --add-module=`realpath ../nginx-ct-master`
make  # NOTE: when I tried building with -jN for speedup I encountered linker issues
sudo make install
cd ..

The rest of the commands in that tutorial should be able to be followed as-is.

A last alternative

Alternatively, you could try to use BoringSSL, since nginx-ct supports that, though it seems you would have to build it from source.