diff options
Diffstat (limited to 'hurd')
| -rw-r--r-- | hurd/subhurd.mdwn | 31 |
1 files changed, 25 insertions, 6 deletions
diff --git a/hurd/subhurd.mdwn b/hurd/subhurd.mdwn index 5b132604..84372dd1 100644 --- a/hurd/subhurd.mdwn +++ b/hurd/subhurd.mdwn @@ -1,12 +1,13 @@ -[[!meta copyright="Copyright © 2007, 2008 Free Software Foundation, Inc."]] +[[!meta copyright="Copyright © 2007, 2008, 2010 Free Software Foundation, +Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled -[[GNU Free Documentation License|/fdl]]."]]"""]] +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] A sub-Hurd is like a [[neighbor_Hurd|neighborhurd]], however, makes use of some resources provided by another Hurd. For instance, backing store and the @@ -17,7 +18,8 @@ attach to them with gdb from the parent ([[debugging_via_subhurds|debugging/subhurd]]). This avoids deadlock, e.g., when the instance of gdb stops the server but requires its use. (Note: it is possible to use [[debugging/gdb/noninvasive_debugging]], but this is less -flexible.) +flexible.) Vice versa, it is also possible to use a subhurd to debug the +*main* Hurd system, for example, the latter's root file system. # Howto @@ -105,9 +107,9 @@ inside the subhurd, or to `ssh` directly into the subhurd. If you want to access the subhurd processes from the outside, e.g. for [[debugging_purposes|debugging/subhurd]] (or to get rid of a subhurd that -didn't exit cleanly...), you need to find out how main Hurd PIDs correspond to +didn't exit cleanly...), you need to find out how main Hurd [[PID]]s correspond to subhurd processes: the subhurd processes appear in the main Hurd (e.g. if doing -`ps -e`) as unknown processes, and vice versa, but the PIDs are different! To +`ps -e`) as unknown processes, and vice versa, but the [[PID]]s are different! To find out which process is which, you can simply compare the order -- while the numbers are different, the order should usually match. Often it also helps to look at the number of threads (e.g. using `ps -l`), as many servers have very @@ -119,3 +121,20 @@ characteristic thread counts. Read about using a subhurd for [[debugging_purposes|debugging/subhurd]]. Roland's tutorial about [[running_a_subhurd]]. + + +# Use Cases + +## Debugging the *Main* Hurd System + +A subhurd can be used for debugging the *main* Hurd system. This works as long +as the subhurd doesn't use any services provided by the main Hurd. For +example, if you already have a subhurd running at the time it happens, you can +use that one to debug a deadlocked [[translator/ext2fs]] root file system in +the *main* Hurd. + +For this, you need to get a handle to the main Hurd's [[ext2fs +translator|translator/ext2fs]]'s [[PID]], but this is no problem, as currently +[[PID]]s are visible across subhurd boundaries. (It is a [[!taglink +open_issue_hurd]] whether this is the right thing to do in +[[open_issues/virtualization]] contexts, but that's how it currently is.) |