Hi,
I have a little problem here...
I had a hardware failure. Replaced the power supply and then the
system wouldn't boot. I eventually bought a new computer, new SSD for
a root/boot disk. Did a fresh install then moved over the storage
drives and went on my merry way....
Now... it seems after an earlier migration I had fogotten to move the
postgresql backup to the new postgresql installation.
So now I have my database in version 9.5 in /oldroot/.... somewhere
and a new instance of psql (Version 12) is running in the freshly
installed instance.
My plan-of-attack is to simply chroot to /oldroot, start the old 9.5
server run a psqldump and un-dump into the new server (have to figure
out how, but should be documented)
But the problem is: how do I start the server in the old root?
All searches for "chroot postgresql" turn up people who, for security
reasons, want to run postgresql inside a chroot environment.
All searches for "start postgresql" tell me to simply type "service
postgresql start". Great on a normal system, but not here:
abra2:/etc# service postgresql start
* Starting PostgreSQL 9.5 database server
* The PostgreSQL server failed
to start. Please check the log output:
2020-11-20 10:54:59 CET [2080825-1] FATAL: could not open shared memory
segment "/PostgreSQL.1552904327": Function not implemented
[fail]
abra2:/etc# journalctl
No journal files were found.
-- No entries --
OK. One step further. Monted (bind) /dev onto /oldroot/dev and now the
message chages to "permission denied" as opposed to "function not
implemented".
One of the things I'd like to do is to start the server manually.
In /lib/systemd/system I find [email protected] that says:
# systemd service template for PostgreSQL clusters. The actual instances will
# be called "postgresql@version-cluster", e.g. "[email protected]". The
# variable %i expands to "version-cluster", %I expands to "version/cluster".
# (%I breaks for cluster names containing dashes.)
and:
ExecStart=@/usr/bin/pg_ctlcluster postgresql@%i --skip-systemctl-redirect %i
start
So, I figured out that my cluster is called "main" and my version
is 9.5. So now I expect that commandline to expand to:
/usr/bin/pg_ctlcluster [email protected] --skip-systemctl-redirect 9.5-main
start
And when I try that I get:
Error: specified cluster does not exist
Now that error message is less useful than it could be. I don't know
if the [email protected] or the 9.5-main is what it considers the
"specified cluster". Anyway, I tried a few variations but can't
get it to recognize the "specified cluster".
abra2:/lib/systemd/system# pg_lsclusters
Ver Cluster Port Status Owner Data directory Log file
9.5 main 5432 down postgres /var/lib/postgresql/9.5/main
/var/log/postgresql/postgresql-9.5-main.log
abra2:/lib/systemd/system#
Simplifying the commandline to:
/usr/bin/pg_ctlcluster 9.5-main start
it seems to do something... but then again:
FATAL: could not open shared memory segment "/PostgreSQL.964036999":
Permission denied
So then running strace -f to see what failed... No EPERM returns from
any system call. Sigh.
So... Any ideas for helping me get my server up-and-running for five
minutes to run a pgdump ?
Roger.
--
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