SharedRLibrary..Rmd

---
title: "Shared R libraries"
author: "Paul Melloy"
date: "`r Sys.Date()`"
output: html_document
---

Frequently when setting up a new virtual machine online to run a shiny server
I run into issues that the shiny server can't run because it can't access the 
users library.
The shiny server runs on the 'shiny' user and can't access my 'paul' user R 
library.  

There are many way to solve this, however one way is to have a shared library
between me 'paul' and the 'shiny' user.

Log into the terminal in the background and create a new folder.
```{bash eval=FALSE, echo=TRUE}
sudo mkdir /home/shared
```

Change the permissions on the shared folder to the user's group.  

```{bash eval=FALSE, echo=TRUE}
#change group ownership to users
sudo chgrp users /home/shared 

# change permissions to drwxrwxr--
# the owner 'root' and group 'users' to read write execute and others read only
sudo chmod 774 /home/shared

# set group ids for and new subdirectories
sudo chmod +s /home/shared
```

Check that 'shiny' and 'paul' are in the 'users' group, and add them if not  

```{bash eval=FALSE, echo=TRUE}
grep 'users' /etc/group

# add them if missing
sudo usermod -a -G users paul
sudo usermod -a -G users shiny
```

copy all 'paul's libraries to `shared/r_libs`

```{bash eval=FALSE, echo=TRUE}
cp -a /home/paul/R/x86_64-pc-linux-gnu-library/. /home/shared/r_libs/
```

While we could edit the system path variables in `/usr/lib/R/etc/Renviron.site`. 
I am not yet comforatble messing with the system variables, and this might 
interrupt additional users of the machine down the line.  
Instead I will add the library to the user `.Renviron`  

```{bash eval=FALSE, echo=TRUE}
echo "/home/shared/r_libs/" >> /home/paul/.Renviron
```

Then add the following to the top of a shiny `app.R` file.

```{r eval=FALSE, echo=TRUE}
.libPaths("/home/shared/r_libs/4.4/")

# Or
if(system("whoami") == "shiny"){
  .libPaths("/home/shared/r_libs/4.4/")
}

```