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- This file contains answers to some questions that are frequently asked
- in the Amanda mailing lists, specially by new users. Please take a
- look at this file before posting, this can save us time that could be
- spent improving Amanda and its documentation.
-
- New entries and modifications are welcome; send them to
- amanda-users@amanda.org or amanda-hackers@amanda.org.
-
- You may also want to take a look at Oren Teich's Amanda FAQ Page,
- http://ugrad-www.cs.colorado.edu/~teich/amanda
-
- He is no longer maintaining that page, but it still contains useful
- and accurate information.
-
-
- Q: Why does Amanda fail to build on my system?
-
- A: One of the most common reasons for compile-time errors is stale
- information in `config.cache', after a build on a different platform
- using the same build tree. In order to avoid this problem, make sure
- you don't ever reuse build trees across platforms, or at least run
- `make distclean' before running `configure' on another platform.
-
- Another common reason for failure, that causes link-time errors, is
- a problem in libtool that causes it to search for symbols in
- already-installed amanda libraries, instead of in the just-built ones.
- This problem is known to affect SunOS 4.1.3 and FreeBSD. You can
- usually work around it by specifying a different prefix when you
- configure the new version of Amanda. However, it may not work if the
- previous version of Amanda was installed in /usr/local and gcc
- searches this directory by default; in this case, you must either
- remove the old libraries (which you don't want to do, right? :-) or
- call configure with the flag --disable-libtool. In this case, Amanda
- won't create shared libraries, so binaries will be larger, but you may
- worry about that later.
-
- You may also want to take a look at docs/SYSTEM.NOTES, as well as
- to the Amanda Patches Page (check www.amanda.org) for other known
- problems. If everything fails, you should read the manual, but since
- we don't have one yet, just post a help request to the amanda-users
- mailing list, showing the last few lines of the failed build.
-
-
- Q: Why does `amdump' report that all disks failed?
-
- A: Probably because the Amanda clients are not properly configured.
- Before you ever run `amdump', make sure `amcheck' succeeds. When it
- does, so should `amdump'.
-
- Make sure you run `amcheck' as the same user that is supposed to
- start `amdump', otherwise you may get incorrect results.
-
-
- Q: Why does `amcheck' say `port NNN is not secure'?
-
- A: Because `amcheck', as some other Amanda programs, must be installed
- as setuid-root. Run `make install' as `root', or `chown' all Amanda
- setuid programs to `root', then `chmod u+s' them again, if `chown'
- drops the setuid bit.
-
-
- Q: Why does `amcheck' claim that the tape is `not an amanda tape'?
-
- A: Because Amanda requires you to label tapes before it uses them.
- Run `amlabel' in order to label a tape.
-
- If, even after labeling a tape, `amcheck' still complains about it,
- make sure the regular expression specified in amanda.conf matches the
- label you have specified, and check whether you have configured
- non-rewinding tape devices for Amanda to use. For example, use
- /dev/nrst0 instead of /dev/rst0, /dev/rmt/0bn instead of /dev/rmt/0b,
- or some other system-dependent device name that contains an `n',
- instead of one that does not. The `n' stands for non-rewinding.
-
- If you have labeled any tapes using the rewiding device
- configuration, you'll have to label them again.
-
-
- Q: Why does `amcheck' report `selfcheck timed out'?
-
- A: This can occur under several different situations. First, make
- sure this problem is repeatable; if Amanda programs are
- NFS-auto-mounted, some clients may fail to mount the Amanda binaries
- in time.
-
- If the error is repeatable, log into the client, and check whether
- the directory /tmp/amanda exists, and a file named amandad.debug
- exists in there: amandad will create this file whenever it starts. If
- this file does not exist, amandad is not starting properly, or it
- lacks permission to create /tmp/amanda/amandad.debug.
-
- In the latter case, wipe out /tmp/amanda, and amandad should create
- it next time it runs. In the former case, check your inetd
- configuration. Make sure you have added the Amanda services to
- /etc/services, that /etc/inetd.conf was properly configured, and that
- you have signalled inetd to reread this file. Check section 2.2 from
- the INSTALL file for details.
-
- Pay special attention to typos in inetd.conf; error messages will
- probably appear in /var/adm/messages if you have typed the amandad
- program name incorrectly. Make sure the same user that you have
- specified at configure-time (--with-user=<USERNAME>) is listed in
- inetd.conf. Check whether this user has permission to run amandad, as
- well as any shared libraries amandad depends upon, by running the
- specified amandad command by hand, as the Amanda user. If you type
- anything, amandad should abort because it can't read a UDP packet
- from the keyboard.
-
- As soon as you have properly configured inetd.conf so as to run
- amandad, you should no longer get the `selfcheck timed out' message.
-
-
- Q: Why does `amandad.debug' contain `error receiving message'?
-
- A: One possibility is that you have run `amandad' from the command
- line prompt and typed anything instead of waiting for it to time-out:
- in this case, it will try to read a UDP packet from the keyboard, and
- this was reported not to work on most keyboards :-). However, if you
- have run `amandad' as any user other than the one listed in
- `inetd.conf', it may have created a /tmp/amanda directory that the
- Amanda user cannot write to, so you should wipe it out.
-
- Another possibility is that the Amanda service was not properly
- configured as a UDP service; check /etc/services and /etc/inetd.conf.
-
-
- Q: Why does `amcheck' say `access as <username> not allowed...'
-
- A: There must be something wrong with .amandahosts configuration (or
- .rhosts, if you have not configured --with-amandahosts).
-
- First, if the <username> is not what you expect (i.e., not what you
- have specified in the --with-user flag, at configure time), check the
- inetd configuration file: you must have specified the wrong username
- there.
-
- Make sure you specify a fully-qualified domain name in
- .amandahosts/.rhosts; aliases are better avoided, for security
- reasons.
-
-
- Q: Why does `amcheck' report `ip address #.#.#.# is not in the ip list
- list for <hostname>'?
-
- A: Check your DNS configuration tables. In order to avoid
- DNS-spoofing, Amanda double-checks hostname<->IP address mapping. If
- the IP address the request comes from maps to a hostname, but this
- hostname does not map back to the incoming IP address, the request is
- denied.
-
-
- Q: Why does `amcheck' say `cannot overwrite active tape'?
-
- A: Because, if you configure Amanda to use N tapes, by setting
- tapecycle to N in `amanda.conf', before Amanda overwrites a tape, it
- must write to at least other N-1 tapes. Of course, Amanda will always
- refuse to overwrite a tape marked for `noreuse' with `amadmin'.
- Furthermore, such tapes are not counted when Amanda computes `N-1'
- tapes.
-
- If, for some reason, you want to tell Amanda to overwrite a
- particular tape, regardless of its position in the cycle, use
- `amrmtape'. This command will remove this tape from the `tapelist'
- file, that is used to manage the tape cycle, and will delete
- information about backups stored in that tape from the Amanda
- database.
-
-
- Q: Why does `amcheck' tell me `DUMP program not available'?
-
- A: Because the `configure' could not find DUMP when it was first run.
- This is a common problem on Linux hosts, because most Linux
- distributions do not install DUMP by default.
-
- If you don't have a DUMP program installed, install it, remove
- `config.cache', run `configure' again and rebuild Amanda. While
- `configure' is running, make sure it can find the installed DUMP
- program. If it cannot, you may have to set the environment variables
- DUMP and RESTORE by hand, before running configure.
-
- If you can't or don't want to install DUMP, you may use GNU tar,
- but make sure it as release 1.12 or newer; release 1.11.8 may work,
- but estimates will be slow as hell.
-
-
- Q: Which tape changer configuration should I use in amanda.conf?
-
- A: If you only have one tape unit, you have two choices: (i) don't use
- a tape changer at all, i.e., set runtapes to 1, set tapedev to the
- non-rewinding device corresponding to the tape unit, and comment out
- tpchanger, changerfile and changerdev; or (ii) set up chg-manual, so
- that you can change tapes manually. If you select chg-manual, you
- will not be able to start `amdump' as a cron job, and you should
- always run `amflush -f', because chg-manual will ask you to press
- return in the terminal where you started the controlling program.
-
- If you have several tape units, which you want to use to emulate a
- tape changer, you want chg-multi. Even if you do own a real tape
- changer, that operates based on ejecting a tape or such, chg-multi may
- be useful.
-
- Actual tape changers usually require specialized changer programs,
- such as `mtx', `chio' or specific system calls. The availability of
- these programs is much more dependent on the operating system you're
- running than on the particular tape changer hardware you have.
-
- `mtx', for example, is available for several platforms. However,
- even if you find it for your platform, beware that there exist several
- different programs named `mtx', that require different command line
- arguments, and print different output, and Amanda's chg-mtx does not
- support them all. You may have to edit the script, which shouldn't be
- hard to do.
-
- In section BUILT-IN TAPE CHANGERS of docs/TAPE.CHANGERS, you will
- find details about the tape changer interfacing programs provided with
- Amanda, that can interact with common tape changer programs and with
- tape changer-related system calls provided by some operating system.
- If none of them matches your needs, you may have to develop your own
- tape changer interface script.
-
- Before posting a question to the Amanda mailing lists, *please*
- search the archives, and try to obtain as much information about
- driving your tape changer hardware from the vendor of the changer
- hardware and of the operating system, rather than from the Amanda
- mailing lists. We usually don't have much to say about tape changer
- units, and several questions about them remain unanswered. :-(
-
- Anyway, if you decide to post a question, make sure you specify
- both the tape changer hardware *and* the OS/platform that is going to
- interface with it. Good luck! :-)
-
-
- Q: Should I use software or hardware compression?
-
- A: When you enable software compression, you drastically reduce the
- compression that might be achieved by hardware. In fact, tape drives
- will usually use *more* tape if you tell them to try to further
- compress already compressed data.
-
- Thus, you must choose whether you're going to use software or
- hardware compression; don't ever enable both unless you want to waste
- tape space.
-
- Since Amanda prefers to have complete information about tape sizes
- and compression rates, it can do a better job if you use software
- compression. However, if you can't afford the extra CPU usage, Amanda
- can live with the unpredictability of hardware compression, but you'll
- have to be very conservative about the specified tape size, specially
- if there are filesystems that contain mostly uncompressible data.
-
-
- Q: How can I configure Amanda so that it performs full backups on the
- week-end and incrementals on weekdays?
-
- A: You can't. Amanda doesn't work this way. You just have to tell
- Amanda how many tapes you have (tapecycle), and how often you want it
- to perform full backups of each filesystem (dumpcycle). It will
- spread full backups along the dumpcycle, so you won't have any
- full-only or incremental-only runs.
-
-
- Q: What if my tape unit uses expensive tapes, and I don't want to use
- one tape per day? Can't Amanda append to tapes?
-
- A: It can't, and this is good. Tape drives and OS drivers are
- (in)famous for rewinding tapes at unexpected times, without telling
- the program that's writing to them. If you have a month's worth of
- backups in that tape, you really don't want them to be overwritten, so
- Amanda has taken the safe approach of requiring tapes to be written
- from the beginning on every run.
-
- This can be wasteful, specially if you have a small amount of data
- to back up, but expensive large-capacity tapes. One possible approach
- is to run amdump with tapes only, say once a week, to perform full
- backups, and run it without tape on the other days, so that it
- performs incremental backups and stores them in the holding disk.
- Once or twice a week, you flush all backups in the holding disk to a
- single tape.
-
- If you don't trust your holding disk, and you'd rather have all
- your data on tapes daily, you can create an alternate configuration,
- with two tapes, that backs up the holding disk only, always as a full
- backup. You'd run this configuration always after your regular
- backup, so you always have a complete image of the holding disk on
- tape, just in case it fails.
-
-
- Q: How can I configure Amanda for long-term archiving?
-
- A: The best approach is to create a separate configuration for your
- archive backups. It should use a separate set of tapes, and have all
- dumptypes configured with `record no', so it doesn't interfere with
- regular backups.
-
-
- Q: Can I backup separate disks of the same host in different
- configurations?
-
- A: Yes, but you have to be careful. Amanda uses UDP to issue estimate
- and backup requests and, although replies to backup requests are
- immediate (so that TCP connections for the actual backup can be
- established), replies to estimate requests are not and, while one
- request is being processed, any other request is ignored. The effect
- is two-fold: (i) if another configuration requests for estimates, the
- request will be ignored, and the requester will end up timing out;
- (ii) if another configuration has already finished the estimates, and
- is now requesting for backups, the backup requests will time-out.
-
- So, there are two easy ways out: (i) ensure that the configurations
- never run concurrently, or (ii) set up two different installations of
- the Amanda server, using different services names to contact the
- clients, i.e., different port numbers. This can be attained with the
- configure flag --with-testing=<service-suffix>. Yes, the flag name is
- not appropriate, but so what?
-
- If you don't want to set up two installations of Amanda (I agree,
- it's overkill), but you still want to back up disks of the same host
- in separate configurations, you can set up Amanda so that one
- configuration only starts after the first one has already finished its
- One possible way to work-around this limitation is to start one
- configuration only after you know the estimates for the first one have
- already finished (modifying the crontab entries, according to history
- data). You'll also have to delay the starttime (a dumptype option) of
- the disks in the first configuration, so that they don't start backing
- up before the estimates of the second configuration finish.
-
-
- Q: Can Amanda span large filesystems across multiple tapes?
-
- A: Not yet :-(
-
- This is an open project, looking for developers. If you'd like to
- help, please take a look at the Amanda Ongoing Projects Page, where
- more up-to-date information is likely to be found about this project.
-
- The current work-around is to use GNU tar to back up subdirectories
- of the huge filesystem separately. But be aware of the problems
- listed in the next question:
-
-
- Q: What's the difference between option `skip-full' and `strategy nofull'?
-
- A: `strategy nofull' is supposed to handle the following situation:
- you run a full dump off-line once a millenium :-), because that disk
- isn't supposed to change at all and, if it does, changes are minimal.
- Amanda will run only level 1 backups of that filesystem, to avoid the
- risk of overwriting a level 1 backup needed to do a restore.
- Remember, you run full dumps once a millenium, and your tape cycle
- probably won't last that long :-)
-
- `skip-full', OTOH, is supposed to let the user run full dumps
- off-line regularly (i.e., as often as specified in the dumpcycle),
- while Amanda takes care of the incrementals. Currently, Amanda will
- tell you when you're supposed to run the level 0 backups but, if you
- fail to do so, Amanda will not only skip a full day's worth of
- valuable backups of the filesystem, on the day it told you to the full
- backup manually, but it will also run a level 1 backup on the next
- day, even if you have not performed the full backup yet. Worse yet:
- it might perform a level 2 on the next day, just after you have run
- the level 0, so, if the disk should crash, you'd have to restore a
- level 0 then a level 2, but not the level 1! Not a real problem, but
- definitely strange, eh?
-
-
- Q: Why does `amdump' report `results missing'?
-
- A: One of the possible reasons is that you have requested too many
- backups of the host. In this case, the estimate request or the reply
- may not fit in a UDP packet. This will cause Amanda not to perform
- some of the backups. Fixing this problem involves modifying the way
- estimate requests are issued, so that no packet exceeds the maximum
- packet size, and issuing additional requests that did not fit in a UDP
- packet after a reply for the previous set is obtained.
-
- One possible work-around is to try to shorten the pathnames of the
- directories and the exclude file names, so that more requests fit in
- the UDP packet. You may create short-named links in some directory
- closer to the root (/) so as to reduce the length of names. I.e.,
- instead of backing up /usr/home/foo and /usr/home/bar, create the
- following links:
- /.foo -> /usr/home/foo
- /.bar -> /usr/home/bar
- then list /.foo and /.bar in the disklist.
-
- Another approach is to group sub-directories in backup sets,
- instead of backing up them all separately. For example, create
- /usr/home/.bkp1 and move `foo' and `bar' into it, then create links so
- that the original pathnames remain functional. Then, list
- /usr/home/.bkp1 in the disklist. You may create as many `.bkp<N>'
- directories as you need.
-
- A simpler approach, that may work for you, is to backup only a
- subset of the subdirectories of a filesystem separately. The others
- can be backed up together with the root of the filesystem, using an
- exclude list that prevents duplicate backups.
-
-
- Q: Why does `amdump' report `disk offline'?
-
- A: Well, assuming the disk is not really off line :-), it may be a
- permission problem, but then, `amcheck' would have reported it.
-
- Another possible reason for this failure is a filesystem error,
- that causes DUMP to crash before it estimates the backup size; a
- `fsck' may help.
-
- Yet another possibility is that the filesystem is so large that the
- backup program is incorrectly reporting the estimated size, for
- example, by printing a negative value that Amanda will not accept as a
- valid estimate. If you are using DUMP, contact your vendor and
- request a patch for dump that fixes this bug. If you are using GNU
- tar, make sure it is release 1.12 or newer; 1.11.8 won't do! Even
- release 1.12 may require a patch to correctly report estimates and
- dump sizes; check the patches directory of the Amanda distribution.
-
-
- Q: What if `amdump' reports `dumps way too big, must skip incremental
- dumps'?
-
- A: It means Amanda couldn't back up some disk because it wouldn't fit
- in the tape(s) you have configured Amanda to use. It considered
- performing some incrementals instead of full dumps, so that all disks
- would fit, but this wouldn't be enough, so the disk really had to be
- dropped in this run.
-
- In general, you can just ignore this message if it happens only
- once in a while. Low-priority disks are discarded first, so you'll
- hardly miss really important data.
-
- One real work-around is to configure Amanda to use more tapes:
- increase `runtapes' in `amanda.conf'. Even if you don't have a real
- tape changer, you can act yourself as a changer (`chg-manual'; more
- details in the question about tape changer configuration), or use
- `chg-multi' with a single tape unit, and lie to Amanda that it will
- have two tapes to use. If you have a holding disk as large as a tape,
- and configure Amanda (2.4.1b1 or newer) not to reserve any space for
- degraded dumps, dumps that would be stored in the second tape of a run
- will be performed to the holding disk, so you can flush them to tape
- in the morning.
-
-
- Q: `amdump' reported `infofile update failed'. What should I do?
-
- A: Make sure all directories and files are readable and writable by
- the Amanda user, within the directory you specified as `infofile' in
- `amanda.conf'. From then on, only run amanda server commands
- (amadmin, amdump, amflush, amcleanup) as the Amanda user, not as root.
-
-
- Q: Why does `amrecover' report `no index records' or `disk not found'?
-
- A: The most common cause of this problem is not having enabled index
- generation in amanda.conf. The `index yes' option must be present in
- every dumptype for whose disks indexes should be generated.
-
- Another possibility is that `amrecover' is not selecting the
- configuration name that contains the backups for the selected disk.
- You may specify a configuration name with the `-c' switch, when you
- invoke `amrecover'. The default configuration name can only be
- specified at Amanda configure time (--with-config=<name>).
-
- Indexes are currently generated at backup-time only, so, if a
- backup was performed without creating an index, you won't be able to
- use `amrecover' to restore it, you'll have to use `amrestore'.
-
-
- Q: Ok, I'm done with testing Amanda, now I want to put it in
- production. How can I reset its databases so as to start from
- scratch?
-
- A: First, remove the `curinfo' database. By default, it is a
- directory, but, if you have selected any other database format (don't,
- they're deprecated), they may be files with extensions such as .dir
- and .pag.
-
- Then, remove any log files from the log directory:
- log.<TIMESTAMP>.<count> and amdump.<count>. Finally, remove the
- tapelist file, stored in the directory that contains amanda.conf,
- unless amanda.conf specifies otherwise. Depending on the tape changer
- you have selected, you may also want to reset its state file.
-