Swap question

Question

I have the following scenario in vfstab and wanna make sure it's correct:
/dev/vx/dsk/swapvol - - swap - no -
and there is no definition in the vfstab for swap such as:
swap - /tmp tmpfs - yes -
Would it be correct to only use the first line in vfstab??
thx.

Answer 1

Its technically correct to only have the first line in your /etc/vfstab file BUT ... I doubt that's what you really want.
The first line tells the system where swap is reside. The "swap - /tmp tmpfs - yes -" line says to mount the /tmp directory as a tmpfs file system on the swap partition - its a bit more complicated then that but that's it at a basic level. That means the /tmp directory uses memory for it storage requirements.
If you don't have /tmp mounted as tmpfs, then /tmp will reside in the root file system which is just fine and dandy. But you could have problems where /tmp could use up all the storage space available in root (/).
In short, you want the second line.
You may want to restrict how much memory /tmp can use by applying a size flag to the second line. This is a very good idea. Read up on the mount_tmpfs man page. It will tell you how to do this.