[CentOS] When should I reboot?

Sat Apr 13 08:52:28 UTC 2019
Tony Mountifield <tony at softins.co.uk>

In article <A39602BA6D703571AC020AA0@[]>,
Kenneth Porter <shiva at sewingwitch.com> wrote:
> I reboot when I yum update to a new kernel or systemd, which seems to come 
> out about once a month. Should I do it for this week's glibc? Is that 
> "core" enough to justify a reboot or should I wait for the next kernel 
> update? I know the glibc update was mainly to handle the new Japanese 
> calendar, so that shouldn't affect my usage. So my question is more about 
> how shared libraries work and whether anything bad would happen with 
> different forks of running services (mainly the mail suite with dovecot and 
> the various content scanners launched by sendmail) running different 
> versions of the library based on when they were started. 

That shouldn't matter. The running programs will have mapped the original
glibc into memory, which will create a reference to the original inode, even
though the directory entries pointing to it are gone. See the output of "lsof"
for one of those processes, and you will see the libraries tagged as (deleted).

Any program started after the glibc update will open and map the new libraries,
independently of any open instances of the old ones.

Both old and new libraries will occupy their own separate disk space until the
last reference to the old library is closed, by terminating all programs using
it, at which time the disk space occupied by the old libraries will be released.

Tony Mountifield
Work: tony at softins.co.uk - http://www.softins.co.uk
Play: tony at mountifield.org - http://tony.mountifield.org