[JshWright]

You can check to see if any running process are using any stale libraries pretty easily:

sudo lsof | grep lib | grep DEL

You can then either reload those processes manually, or just bounce the box if that's easier.

[gtrubetskoy]

There's also a rare chance that a program is statically linked, in which case upgrading glibc won't help, the program would need to be recompiled.

[JshWright]

Yeah, that's a good point, and definitely worth mentioning, but obviously rebooting isn't going to help in that case either. The parent was asking about how they would know if they need to reboot or not.

[aidenn0]

It is nearly impossible to statically link glibc.

[cnvogel]

... with nss-modules being a major culprit, ironically... (on which gethostbyname relies greatly)...