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Diffstat (limited to 'Documentation/filesystems/nfs')
| -rw-r--r-- | Documentation/filesystems/nfs/nfs.txt | 44 |
1 files changed, 41 insertions, 3 deletions
diff --git a/Documentation/filesystems/nfs/nfs.txt b/Documentation/filesystems/nfs/nfs.txt index f50f26ce6cd0..f2571c8bef74 100644 --- a/Documentation/filesystems/nfs/nfs.txt +++ b/Documentation/filesystems/nfs/nfs.txt @@ -12,9 +12,47 @@ and work is in progress on adding support for minor version 1 of the NFSv4 protocol. The purpose of this document is to provide information on some of the -upcall interfaces that are used in order to provide the NFS client with -some of the information that it requires in order to fully comply with -the NFS spec. +special features of the NFS client that can be configured by system +administrators. + + +The nfs4_unique_id parameter +============================ + +NFSv4 requires clients to identify themselves to servers with a unique +string. File open and lock state shared between one client and one server +is associated with this identity. To support robust NFSv4 state recovery +and transparent state migration, this identity string must not change +across client reboots. + +Without any other intervention, the Linux client uses a string that contains +the local system's node name. System administrators, however, often do not +take care to ensure that node names are fully qualified and do not change +over the lifetime of a client system. Node names can have other +administrative requirements that require particular behavior that does not +work well as part of an nfs_client_id4 string. + +The nfs.nfs4_unique_id boot parameter specifies a unique string that can be +used instead of a system's node name when an NFS client identifies itself to +a server. Thus, if the system's node name is not unique, or it changes, its +nfs.nfs4_unique_id stays the same, preventing collision with other clients +or loss of state during NFS reboot recovery or transparent state migration. + +The nfs.nfs4_unique_id string is typically a UUID, though it can contain +anything that is believed to be unique across all NFS clients. An +nfs4_unique_id string should be chosen when a client system is installed, +just as a system's root file system gets a fresh UUID in its label at +install time. + +The string should remain fixed for the lifetime of the client. It can be +changed safely if care is taken that the client shuts down cleanly and all +outstanding NFSv4 state has expired, to prevent loss of NFSv4 state. + +This string can be stored in an NFS client's grub.conf, or it can be provided +via a net boot facility such as PXE. It may also be specified as an nfs.ko +module parameter. Specifying a uniquifier string is not support for NFS +clients running in containers. + The DNS resolver ================ |