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Re: OID and filesystem issues

From: lfedden(at)contextworld(dot)com
To: tgl(at)sss(dot)pgh(dot)pa(dot)us
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: OID and filesystem issues
Date: 2008-04-15 15:25:22
Message-ID: 4F91850CA8.07DC00FATFSFQGQL@contextworld.com (view raw or flat)
Thread:
Lists: pgsql-admin
Hi Tom,
Thanks for your reply.

I did mean the data/OIDs from the relfilenode column in pg_class.

Even when logged in as root, a 'ls -l' command returns:

mm2:/var/lib/pgsql82/data/base/16673 # ls -lash | more
/bin/ls: 19357877: Permission denied
/bin/ls: 19569529: Permission denied
/bin/ls: 19569531: Permission denied
/bin/ls: 19569533: Permission denied
/bin/ls: 19614956: Permission denied
/bin/ls: 19716858: Permission denied
total 124G
  68K drwx------ 2 postgres postgres   68K 2008-04-15 15:52 .
    0 drwx------ 6 postgres postgres   144 2007-06-22 17:20 ..
 7.0M -rw------- 1 postgres postgres  7.0M 2008-04-12 19:51 10163089
    0 -rw------- 1 postgres postgres     0 2007-10-24 10:45 10163091
  24K -rw------- 1 postgres postgres   24K 2008-02-28 10:19 10264430
etc...

And when I tried to change the owner or file permissions (still as root):

mm2:/var/lib/pgsql82/data/base/16673 # chown postgres.postgres 19716858
chown: cannot access `19716858': Permission denied

mm2:/var/lib/pgsql82/data/base/16673 # chmod u+rw 19716858
chmod: cannot access `19716858': Permission denied

So can we assume it is safe to remove these none accessible files and also the couple of orphaned OID files from pg_class we can still access?

Are there any known situations that could cause such issues or anyway we could track back and see how this happened? I'm keen to prevent anything like this happening again in the future.

Thanks
Lee.


 -----Original Message-----
From: tgl(at)sss(dot)pgh(dot)pa(dot)us
Sent: 15 April 2008 15:44
To: Lee Fedden
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: [ADMIN] OID and filesystem issues


   

 --------------------------------------------------------------------------  --
lfedden(at)contextworld(dot)com writes:
> 1) Does every relation exist in pg_class? Can we assume that if there
is a file with OID which is not present in pg_class, this file can be
deleted? (we have a few such files, some of them take more than 2G of
space in total)

You do know it's relfilenode that counts, not OID?

As long as you are paying attention to the right column, yes, you could
remove any file that doesn't correspond to a live pg_class row.  It's
not a common situation though so I'd definitely triple-check first.

> 3) We have a relation which is unaccessible (permission denied), ls -l
also prints this message so it's something with filesystem. What would be 

the best procedure to solve this issue ?

Fix the ownership/permissions with chown/chmod, as needed.  Pretty much
all files in a database should be alike in this regard (postgres-owned,
mode 0600).

   regards, tom lane

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