Thanks for this. Brings back so many memories of the long hours spent in computer rooms with HP 9000s and RS/6000s back in the 90s. Seeing that SAM interface made me shiver :)
It's great that there are folks like you preserving this history
The "context dependent filesystem" concept is a bit trippy, but I think it's a pretty neat solution to "some systems need a their own version of a file, other files ought to be universal".
It reminds me a little of a thing used in clustering of DECs (later HPs) Tru64 Unix.
The clusters had a shared OS image - that is a single, shared root filesystem for all members. To allow node-specific config files, there was a type of symbolic link called a “Context Dependent Symbolic Link” (CDSL). They were just like a normal symlink, but had a `{memb}` component in the target, which was resolved at runtime to the member ID of the current system. These would be used to resolve to a path under `/cluster/members/{memb}`, so each host could have its own version of a config file.
The single shared root filesystem made upgrades and patching of the OS extra fun. There was a multi-phase process where both old and new copies of files were present and hosts were rebooted one at a time, switching from the old to the new OS.
>I’ve got my HP 9000 Model 340 booting over the network from an HP 9000 Model 705 in Cluster Server mode and I’ve learned some very unsettling things about HP-UX and its filesystem.
>Boot-up video at the end of the blog, where I play a bit of the original version of Columns.
Thanks for this. Brings back so many memories of the long hours spent in computer rooms with HP 9000s and RS/6000s back in the 90s. Seeing that SAM interface made me shiver :)
It's great that there are folks like you preserving this history
The "context dependent filesystem" concept is a bit trippy, but I think it's a pretty neat solution to "some systems need a their own version of a file, other files ought to be universal".
It reminds me a little of a thing used in clustering of DECs (later HPs) Tru64 Unix.
The clusters had a shared OS image - that is a single, shared root filesystem for all members. To allow node-specific config files, there was a type of symbolic link called a “Context Dependent Symbolic Link” (CDSL). They were just like a normal symlink, but had a `{memb}` component in the target, which was resolved at runtime to the member ID of the current system. These would be used to resolve to a path under `/cluster/members/{memb}`, so each host could have its own version of a config file.
The single shared root filesystem made upgrades and patching of the OS extra fun. There was a multi-phase process where both old and new copies of files were present and hosts were rebooted one at a time, switching from the old to the new OS.
From the author's Reddit post <https://www.reddit.com/r/vintagecomputing/comments/1ot83o4/y...>:
>I’ve got my HP 9000 Model 340 booting over the network from an HP 9000 Model 705 in Cluster Server mode and I’ve learned some very unsettling things about HP-UX and its filesystem.
>Boot-up video at the end of the blog, where I play a bit of the original version of Columns.