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Re: su does not work anymore



On Saturday 02 May 2020 07:19:13 The Wanderer wrote:

> On 2020-05-02 at 06:57, Sven Joachim wrote:
> > On 2020-05-02 10:57 +0200, Rainer Dorsch wrote:
> >> Am Samstag, 2. Mai 2020, 06:32:02 CEST schrieb Andrei POPESCU:
> >>> Ugh. For such situations one should either have good backups or
> >>> a reasonably fast and automated method of reinstalling the
> >>> system.
> >>>
> >>> See also http://taobackup.com
> >>
> >> Thanks for sharing the nice link, Andrei. Unfortunately, I took the
> >> novice approach on step 1 for the system files. I do not see any
> >> issues on the system anymore tough. To be on the saver side, I also
> >> did an "apt-get reinstall" of the relevant packages. I hope the
> >> next "apt-get dist-upgrade" will eliminate any so far hidden
> >> issues.
> >
> > There will likely be a few problems left.  Reinstalling packages
> > fixes the owner and permissions of most ordinary files, but
> > directories are left alone, and some programs (especially daemons)
> > might find themselves unable to write where they are supposed to.
>
> I had to fix my primary system from a more severe version of a similar
> problem, a year or so ago; long story short, when I built the system I
> put /var on a separate RAID array from the rest of the general install
> (because, like /home, it's documented as needing potentially lots of
> space so it didn't seem suited for the smaller-capacity SSD array),
> and when that array died and the data-recovery service gave me my
> files back they had passed the whole thing through a tool that assumes
> and applies a generic Windows-filesystem permission set and mangles
> the filenames into a form that uses only NTFS-legal characters.
>
> It took me three-to-six months of painful, detailed effort, with
> painstaking back-and-forth comparisons against a known-good system and
> lots of manual scripting to redownload the /var/cache/apt/archives/
> contents for verification, to be sure I had everything back together
> to a sufficient degree. Even then, I'm still not sure things are 100%;
> just yesterday, I found a trio of rarely-accessed files (under /home,
> and not config files, fortunately) whose names still had underscores
> in place of colons.
>
> Manual recovery like this *can* be done, but I do not recommend
> embarking upon it without very strong reason. (In my case, I needed to
> fix the filenames and permissions of my entire /home partition anyway,
> and that includes irreplaceable data measuring in terabytes and dating
> in some cases as far back as the '90s. Proper external backup is now
> very much on my radar.)

That leaves amanda, standing alone away from the crowd.  I've used it 
here for over 20 years now as a shorter term solution to getting 
anything back, provided I discover its missing in under 56 or so days.  
I don't use tapes but virtual tapes on a big HD, as real tapes aren't 
near as dependable.  60 of them on a 2T drive ATM.

Drives that aren't shut down don't fail, I have some with nearly 200,000 
spinning hours on them and as good as the day they were first spun up 
decades ago. The Amanda backup scheduler also does not do fulls on 
Friday, but juggles incrementles in an attempt to use about the same 
amount of media for each run. You setup the days of a runcycle and 
amanda juggles the backup levels around while absolutely doing a full on 
every entry in the disklist at least once per runcycle days. It keeps a 
database so it knows what is has and what vtape its in. But with vtapes, 
its not the time consuming sequential tape read to find what it needs as 
the vtape access is random & hundreds of times faster.

I could lose this main drive yet this morning, get in the pickup and run 
up to Staples and get a new drive, bring it back and install linuxcnc 
from the dvd, get that database from last nights backup with tar, 
install amanda, and by 5pm, have this machine back in the exact state it 
was in at this mornings 2AM backup.  Whats not to like?  Have cron run 
it in the wee hours every night and sleep well, knowing you have 
disaster recovery at hand right from your own keyboard.  I'm doing 5 
machines with it. The New York State Dept of Health is doing at least 40 
machines with it.  Cern uses it.  The list goes on.

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>


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