System Files Backup

[posted 2000/01/13]

Over the Christmas weekend, we had an important machine fail.  Nothing Y2K related.  The system disk just died.  :-(

Fortunately, we had a fairly recent backup of the system disk, but it was not fully up-to-date.  And what if we had no backup for some reason?

I have developed another Pikt script to prepare for such situations. Here it is:

#ifndef generic

#  if ! no_usr_local

SysFilesBackupNotice

        init
                status active
                level notice
                task "Do system files backup to a central repository"
                input file "=sysfiles_obj"
                dat $name 1

        begin   // so as not to clobber /usr/local from all machines at
                // once, put in this random pause
                pause #random(3600)     // up to a one-hour pause

        rule    // bypass all but regular text files
                if    ! -f $name
                   || $command("=file $name") !~~ "ascii text"
                        next
                endif

        rule    // get the basename (strip away the directory)
                set $base = $basename($name)

        rule
                =execwait "=cp -p $name /usr/local/etc/precious/$base\." .
                                  $hostname()

#  endif  // ! no_usr_local

#endifdef  // generic

To test this, I followed my usual procedure of registering it as a Test alert in alerts.cfg:

Test
        timing          =piktnever
        mailcmd         "=mailx -s 'PIKT Alert on =pikthostname: Test' pikt-test"
        alarms
                        SysFilesBackupNotice

After installing with

  piktc -iv +A Test +H cologne

I logged into the cologne machine and ran the script directly with

  pikt +A Test

(Actually, for the test, I reduced the pause to #random(60).)

After several minutes, here was the result:

rootcologne:398> ls
./                     hosts.deny.cologne     protocols.cologne
../                    hosts.cologne          resolv.conf.cologne
.rhosts.cologne        inetd.conf.cologne     rpc.cologne
PIKT.conf.cologne      inittab.cologne        services.cologne
aliases.cologne        magic.cologne          shadow.cologne
auto_master.cologne    mnttab.cologne         shells.cologne
defaultrouter.cologne  networks.cologne       syslog.conf.cologne
dfstab.cologne         nsswitch.conf.cologne  termcap.cologne
group.cologne          ntp.conf.cologne       ttydefs.cologne
hostname.le0.cologne   passwd.cologne         vfstab.cologne
hosts.allow.cologne    piktd.conf.cologne

Once satisfied with the result (actually I had to go through several trials until I got everything specified just right), I deleted all traces of the Test script with (on the piktmaster):

  piktc -tv +A Test +H cologne

  processing cologne...
  disabling alert(s)...
  Test disabled
  deleting file(s)...
  Test.alt deleted
  deleting file(s)...
  Test.hst deleted
  deleting file(s)...
  Test.log deleted

Because of the pause, I added this script to the end of the Notice alarms list (in alerts.cfg).  Our Notice alert runs nightly at 3:50 AM, so the "precious" files will get backed up daily before 5 AM.

I hope it's obvious by now, but here is the command I used to install (almost) everywhere:

  piktc -iv +A Notice -H no_usr_local downsys

A few other details.  "=sysfiles_obj" is a macro, specified in macros/piktfiles_obj_macros.cfg, as

  sysfiles_obj            =objdir/SysFiles.obj

I could have specified a separate set of "precious" system files in objects.cfg, but I decided it was most convenient to use the existing SysFiles object list.

Note the '#if ! no_usr_local' wrapper around this script.  'no_usr_local' is a host group defined in systems.cfg for those systems that, for one reason or another, don't have a the commonly shared /usr/local NFS cross-mounted.  This implies that several of our systems won't have their precious files backed up.  I'll get around to fixing this problem one of these days, but that's good enough for the moment.

Now, if a system disk dies, or if an important file gets corrupted, we will have system files backups on-line.

I've done this sort of system files backup before, pre-PIKT, and no doubt you have, too.  But it's never been so easy to manage or as sophisticated as this.

For more examples, see Developer's Notes.