# Starting October 15, Dropbox has fucked all his CentOS 6 (and many other) users 
# by changing OS requirements:
# ----
# We  are  reaching  out  to let you know that device(s) which do not meet our new
# operating  system  requirements  have  been  logged  out  of the Dropbox desktop
# application. Dropbox has ended support for Ubuntu 13.10 and below, and Fedora 20
# and below.
# ...
# Your device(s) must now be on glibc 2.19 or higher to log back into the Dropbox 
# desktop application
# ----
#
# Here is the instruction on how to sort it out w/o migrating to "supported" OSes
# Thanks tacvbo for his post:
# https://www.dropboxforum.com/t5/Syncing-and-uploads/Dropbox-client-warns-me-that-it-ll-stop-syncing-in-Nov-why/m-p/303208/highlight/true#M45240
#
# This instruction should be improved though to support Dropbox autoupdates
#

# become root
sudo bash

# Install latest stable kernel (4.x)
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
rpm -Uvh https://www.elrepo.org/elrepo-release-6-8.el6.elrepo.noarch.rpm
yum-config-manager --enable elrepo-kernel
yum install kernel-ml.x86_64

# modify /etc/grub.conf and reboot into the new kernel

# install new kernel headers and selinux libs into a non-system location
yumdownloader kernel-ml-headers.x86_64
rpm -ihv -r /opt/kernel-ml-headers kernel-ml-headers-4.18.14-1.el6.elrepo.x86_64.rpm
yumdownloader libselinux-devel
rpm -ihv -r /opt/kernel-ml-headers libselinux-devel-2.0.94-7.el6.x86_64.rpm --nodeps

# install gcc 7.3 and patchelf
yum install centos-release-scl patchelf
yum-config-manager --enable rhel-server-rhscl-7-rpms
yum install devtoolset-7

# enable gcc 7.3 and other related stuff
scl enable devtoolset-7 bash

# install latest bison
wget https://ftp.gnu.org/gnu/bison/bison-3.0.4.tar.gz
tar zxf bison-3.0.4.tar.gz
cd bison-3.0.4
./configure --prefix=/opt/bison-3.0.4
make
make install

# prepare new glibc configs
mkdir -p /opt/glibc-2.27/etc/ld.so.conf.d
cp /etc/ld.so.conf /opt/glibc-2.27/etc/
cp /etc/ld.so.conf.d/kernel-ml-4.18.14-1.el6.elrepo.x86_64.conf /opt/glibc-2.27/etc/ld.so.conf.d

# build and install the new glibc
wget https://ftp.gnu.org/gnu/glibc/glibc-2.27.tar.gz
tar xzvf glibc-2.27.tar.gz
cd glibc-2.27
mkdir build
cd build
PATH=$PATH:/opt/bison-3.0.4/bin ../configure --prefix=/opt/glibc-2.27 --with-headers=/opt/kernel-ml-headers/usr/include
PATH=$PATH:/opt/bison-3.0.4/bin make
PATH=$PATH:/opt/bison-3.0.4/bin make install

# become a user who needs to run dropbox
su - user

# install and patch dropbox binary
wget -O - "https://www.dropbox.com/download?plat=lnx.x86_64" | tar xzf -
patchelf --set-interpreter /opt/glibc-2.27/lib/ld-2.27.so  ~/.dropbox-dist/dropbox-lnx.x86_64-59.4.93/dropbox
patchelf --set-rpath /opt/glibc-2.27/lib ~/.dropbox-dist/dropbox-lnx.x86_64-59.4.93/dropbox

# install required libs
ln -s /lib64/libgcc_s.so.1 .dropbox-dist/dropbox-lnx.x86_64-59.4.93/
ln -s /usr/lib64/libstdc++.so.6 .dropbox-dist/dropbox-lnx.x86_64-59.4.93/
ln -s /lib64/libz.so.1 .dropbox-dist/dropbox-lnx.x86_64-59.4.93/
ln -s /lib64/libgthread-2.0.so.0 .dropbox-dist/dropbox-lnx.x86_64-59.4.93/
ln -s /lib64/libglib-2.0.so.0 .dropbox-dist/dropbox-lnx.x86_64-59.4.93/

# make sure you have dropbox.py in the path
# (https://www.dropboxwiki.com/tips-and-tricks/using-the-official-dropbox-command-line-interface-cli)

# run dropbox
LD_LIBRARY_PATH=~/.dropbox-dist/dropbox-lnx.x86_64-59.4.93 dropbox.py start

# check the status
dropbox.py status
Syncing 525 files
Downloading 525 files...