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repair

NAME

repair - Repair conflicts in the Coda Distributed File System

SYNOPSIS

repair -d

repair -allowclear

repair object_in_conflict fixfile [ repair_options ]

DESCRIPTION

The Coda repair tool allows you to manually resolve two kinds of conflicts resulted from partitioned updates. Server-server conflicts are conflicting mutations performed on partitioned servers that can not be automatically resolved. Local-global conflicts are caused by mutations performed on a disconnected client that are in conflict with the global server state.

To use the repair tool interactively, type repair at the command prompt.

Server-Server conflicts can be repaired from the command line without entering interactive mode. This is useful if you need to repair many conflicts within a volume at a time and wish to write a shell script. Please see the EXAMPLES section for examples on invoking complete repair sequences from the command line.

A description of the repair commands follows:

beginrepair object

verifies that object is indeed in conflict. It will print out messages to indicate whether the current repair session is for server-server conflict or local-global conflict.

For a server-server repair session, this command locks the corresponding volume and and mounts its individual replicas read-only. It will inform the users to only use the comparedirs, dorepair and removeinc commands to repair the conflict.

For a local-global repair session, both local and global replicas of object are visible at object/local (read-only) and object/global (mutable and serving as the workspace for storing the repair result for object). You need to iterate through the current sessions local-mutations-list containing all the local updates to object and its descendants. Each operation in local-mutations-list must be accounted for and Venus maintains the current-mutation being iterated. Use the checklocal command to find out the conflict between the current-mutation and the server state. Note that not all local mutations are necessarily in conflict, and you can use the listlocal command to see all the operations in local-mutations-list. You can advance the iteration to the next operation using either the preservelocal or the discardlocal command with the former replaying the current-mutation operation on the relevant global replicas. To speed up the iteration, the preservealllocal command repeats preservelocal until the local-mutations-list is exhausted or the first replay failure. Similarly, the discardalllocal command repeats discardlocal until exhausting the local-mutations-list. You can use external tools such as emacs(1) to make direct updates on needed replicas under object/global. Use the quit command to either commit or abort the session.

quit

If the current session is repairing a server-server conflict, this command releases all the volume-level locks and causes the repair tool to return to the shell. If the current session is repairing a local-global conflict, this command asks you whether to commit or abort the repair session. If you answer yes, the mutations performed on the relevant global replicas will be committed to the servers. Otherwise, the repair result will be aborted as if this repair session has never happened.

help

Prints out a help message.

Use the following commands to repair a server-server conflict:

comparedirs object fixfile [ -acl user rwlidka ] [ -mode newmode ] [ -owner username ]

Compares the mounted read-only replicas of a directory in conflict and prints the repair commands in fixfile to make the replicas identical. To print out the repair commands on your terminal give stdout as the pathname for fixfile. Compensating actions for Name/Name conflicts and Update/Update conflicts are not given. The user is only told about their existence and required to edit the fixfile manually. You should have already done a beginrepair on object and this command works only if object is a directory.

dorepair object fixfile

Does the actual repair of an object. If the repair succeeds, each accessible replica will be marked consistent. You will be prompted for the arguments if they are missing, and will be asked to confirm the repair. You should have already done a beginrepair on this object (or on on some other object in this volume.). If object is a file or symbolic link, fixfile must provide its new contents. If object is a directory, fixfile must provide a sequence of directory repair commands for each replica. The format of fixfile for directories is as follows:

 replica <servername> <id of replica1>
     <repair commands for replica1>
 replica <servername> <id of replica2>
     <repair commands for  replica2>
 and so on
 

Repair commands are given one per line. Blank lines are ok. id of replica1, id of replica2, etc. are numbers that identify each replica. These are the same as the volume ids of read-write volumes corresponding to a replicated volume. The volume ids can be obtained by doing an ls on the inconsistent object, after the beginrepair command has succeeded. The directory repair commands are:

 createf <filename> <fid.0> <fid.1> <fid.2>
 creates <symlinkname> <fid.0> <fid.1> <fid.2>
 createl <linkname> <fid.0> <fid.1> <fid.2>
 created <dirname> <fid.0> <fid.1> <fid.2>
 removefsl  <filename or symlinkname or linkname>
 removed  <dirname>
 mv <srcname> <tgtname>
     <src <fid.0> <fid.1> <fid.2>>
     <target <fid.1> <fid.2>>
 setacl  <username> [rwlikda]
 delacl  <username>
 setmode <newmode>
 setowner <new owner name>
 setmtime <new modified time>
 

Note that for the setacl command, the short form access rights of all and none can also be used.

removeinc object

Removes the inconsistent object if it is file or a symbolic link. If the object is a directory, all the descendants of the object will be removed in all the accessible replicas and the directory itself will be removed as long as its replicas are identical. If the owner or the ACL of the directory replicas are different, you have to repair the conflict first.

clearinc object

Compares the mounted read only replicas of a directory in conflict and if the replicas are identical it clears the inconsistency flag of the replicas. Otherwise it will inform you about the inequality of the replicas. You should run the comparedirs command to find out the cause of conflict. This command should be used only for directories. Files and symbolic links are cleared of their inconsistency with the dorepair command.

The following commands are used only for repairing local-global conflicts:

checklocal

Checks to see if the current-mutation being iterated by the current local-global repair session is in conflict with the server state. It displays the operator and operand (s) of the current-mutation operation and indicates whether it is in conflict with the relevant server replicas. If it is in conflict, a brief reason of the conflict is given. Note that this command does not advance the iteration of the local-mutations-list.

discardlocal

Simply advances the iteration of the local-mutations-list of the current local-global repair session to the next operation. Use this command when the user does not want the current-mutation operation to have any effect on the repair result.

preservelocal

Tries to replay the current-mutation of the current local-global repair session on the relevant global replicas. In other words, it will try to preserve the effect of the current mutation in the repair result. If the replay succeeds, the iteration of local-mutations-list will be advanced to the next operation. The effect of the replay is visible only on this client and not on the server until the repair result is successfully committed. If the replay fails, information about the reason of the failure will be displayed.

discardalllocal

Repeatedly performs the discardlocal command until the local-mutations-list is exhausted. Its effect is to finish the iteration and discard the effect of all the remaining mutations on the repair result.

preservealllocal

Repeatedly performs the preservelocal command until the first failure or the iteration of local-mutations-list is exhausted. This command is used if the user wants to preserve the effect of all the remaining mutation operations in the repair result.

listlocal

Prints out all the mutation operations in the local-mutations-list of the current local-global repair session.

The following commands existed in old versions but are no longer supported:

showreplicas object

Shows the names of the individual replicas of object, and the pathnames by which these replicas may be examined read-only. A beginrepair must have been done earlier on this object (or on another object in the same volume).

unlockvolume pathname

Tells Venus to unlock the specified volume in repair. No check is done to see if you locked the volume during this repair session. The primary use of this command is to unlock volumes that were locked during a previous, aborted, invocation of the repair tool. The command will fail if Venus discovers that you do not hold the repair lock on the server. This could happen, for example, if your aborted repair occurred on another workstation, or if you were not repairing the volume in the first place.

EXAMPLES

This will cause repair to examine the object "common", generate a fix file for it and in addition to the contents of the fix file, and set the acl for hmpierce to rlidwka on the replica.

 repair common /tmp/fix -acl hmpierce all
 

The same repair would look like this in interactive mode:

 repair> beginrepair common
 repair> comparedirs common /tmp/fix -acl hmpierce all
 repair> dorepair common /tmp/fix 
 repair> endrepair
 repair> quit
 

AUTHORS

*

M. Satyanarayanan, 1989, Created

*

Puneet Kumar, 1991, Substantially revised

*

Joshua Raiff, 1993, Created man page

*

Qi Lu, 1995, Added local-global repair commands and revised man page

*

Henry M. Pierce, 1998, updated for command line options