I was recently asked the following question:
How could you reboot the linux server if your root filesystem is not mounted and you cannot mount it (it is lost) and you do not have any binary - you have only root shell.
It has something to do with /proc I assume, but maybe it is not possible at all. Could anyone provide some guidance on what I should do in that situation?
This is how / should be mounted
mount
/dev/md0 on / type ext3 (rw,errors=remount-ro)
but in fact, it is mounted read-only because of unknown reason so far for me.
cat /proc/mounts
/dev/md0 / ext3 ro,relatime,errors=remount-ro,data=ordered 0 0
:/var/log# echo aaa > /tmp/ddd
bash: /tmp/ddd: Read-only file system
As ext3 has errors=remount-ro flag, the possible reason is that the filesystem has errors. When I checked syslog/messages/dmesg I did not find any related information (no disk failures, filesystem errors etc.). This server does not have any iLo or so.
So what do you recommend, how to recover the root filesystem without working physically on the server.
Update:
:/var/log# mount -o remount,rw /
mount: cannot remount block device /dev/md0 read-write, is write-protected
I had to make a symbolic link on one of databases to another location on MySQL (Debian 6.0). So /var/lib/mysql/dbname points to /home/user/dbname, but MySQL gives
MySQL error: 1017 (Can't find file: './dbname/tbl201206.frm' (errno: 13))
I have read some manuals about making symbolic links on data dirs or table files, but can mysqld read also this kind of links?
Simple question, I have 3 hosts running 4.1 Essentials Plus with vmware HA. I tried to create several virtual machines that filled 90% of each server's memory capacity. I know that vmware has really sophisticated memory management within virtual machines, but I do not understand how the vCenter can allow me even to power on the virtual machines that exceed the critical memory level, when the host failover can be still handled.
Is it due to the fact that virtual machines does not use the memory, so that it is still considered as free, so virtual machines can be powered on ? But what would happen if all VMs would be really using the RAM before the host failure - they could not be migrated to other hosts after the failure.
The default behaviour in XenServer is that, it automatically calculates the maximum memory level that can be used within the cluster so that the host failure is still protected. Vmware does the same thing ?
The admission policy is enabled. Vmware HA enabled.
I would be glad guys, if you can answer me some of my questions about the performance of our storage. The setup
Basically, the main reason why I had to look at our storage was the transfer of the monitoring VM from local disks of one of hosts to the storage. So before doing any migration, I setup a new VM with iometer and ran the tests during the night, when there were no important jobs running in the cluster. There was only 1 dynamo worker thread from this VM.
Access Specification Name IOps Read IOps Write IOps MBps Read MBps Write MBps Transactions per Second Average Response Time Average Read Response Time
512B; 100% Read; 0% random 5617.191059 5617.191059 0.000000 2.742769 2.742769 0.000000 5617.191059 0.176979 0.176979
512B; 75% Read; 0% random 3190.524306 2369.761725 820.762581 1.557873 1.157110 0.400763 3190.524306 0.312244 0.321925
512B; 50% Read; 0% random 1055.807449 524.819993 530.987456 0.515531 0.256260 0.259271 1055.807449 0.946000 0.421600
512B; 25% Read; 0% random 1006.956966 239.414257 767.542709 0.491678 0.116901 0.374777 1006.956966 0.853556 0.687116
512B; 0% Read; 0% random 35.123065 0.000000 35.123065 0.017150 0.000000 0.017150 35.123065 28.349538 0.000000
4K; 75% Read; 0% random 3034.296095 2247.847150 786.448945 11.852719 8.780653 3.072066 3034.296095 0.328614 0.333793
4K; 25% Read; 0% random 2237.793260 587.671309 1650.121951 8.741380 2.295591 6.445789 2237.793260 0.445755 0.636275
16K; 75% Read; 0% random 627.852712 474.796322 153.056389 9.810199 7.418693 2.391506 627.852712 1.591288 1.840213
16K; 25% Read; 0% random 478.619741 116.666329 361.953412 7.478433 1.822911 5.655522 478.619741 2.086953 1.281547
32K; 75% Read; 0% random 848.266506 649.372846 198.893660 26.508328 20.292901 6.215427 848.266506 1.176316 1.334378
32K; 25% Read; 0% random 443.441341 117.275291 326.166050 13.857542 3.664853 10.192689 443.441341 2.253707 7.158792
hdparm read tests (with hdparm -t /dev/sda) gave 300MB/s.
Our monitoring system gets information from +- 40 VMs and 30 devices, every host has at least 10 services, but actually that is cacti which generates the majority of IOPS. It massively updates the RRD data simultaneously every minute. Despite this fact, I decided to migrate the VM to the storage. After the migration, I measured the IOPS generated from monitoring - the average value was 800, but the response time after any read operation on every VM was horrible - 5-10 secs, the monitoring actually killed some VMs as the kernel timed out on some IO operations. hdparm gave 1,4MB/sec. I turned off the cacti RRD processing and it runs well, but we have no graphs.
My questions:
1) What do you think about the iometer performance on this setup? It should be better, it is ok, or should I search for some misconfiguration?
2) Do you recommend to have separate physical host with monitoring software and do not "bother" the storage with this kind of IOPS?
3) This question is more general. After the storage test we can get IOPS/mbps for different block sizes. But how can I assess the block size an application is mostly using? For example the databases system is often using 75% read operations, but what is the block size so that I could compare it with my results ? Without knowing this information, my iometer tests are simply just numbers.
UPDATE 1: Thank you for answers.
So what we did, is that we created ramdisk for rrd processing, and all rrds are synced every hour to the monitoring disk. Everything works quite fast, but we will think about creating another RAID group with RAID 10 for this kind of IOPS that need good write performance.
How to get SMART information about local disks (no SmartArray) installed in ESXi host? It is HP DL G6 server, but without the HP Insight Suite.
There is a part of the infrastructure, where I have to do a sw raid on vmware esxi, because the SmartArray controller cannot be added and connection to the storage is not possible as well. So what I plan to do, is to have 3 disks in the server - 1 for booting the esxi and 2 provisioned to the VM, so I could do the sw raid within the OS installation process. So the virtual machine is going to have 2 virtual disks, each from different datastore/physical disks.
The question is, what is the performance impact in this case? (VM is nagios with 100+ checking hosts and services), or should I search for another solution ?
I have an alias which has 20 mails accounts. So when a mail is sent to this alias, everyone receives it. But, when I set a vacation on one of those 20 mail accounts, the autoreply is sent as well. I want to exclude these cases - when the mail has not specific mail account in To: or Cc: header. The script is called vacation.pl and it's from postfixadmin.
Is there any way how to do it except for manual editing the script ?
How can I safely migrate an account from domain to standard local account ? I have a plenty of software installed within this account and I do not want to reinstall it again. I assume there are so many entries in registry that have to be preserved.
I have SQL Server express installed on vCenter, so the maximum size of the database can be only 4GB. I don't know why, but from some moment the size of the db started to grow exponentially, so I have to delete the data which is older than 40days with the script provided on the vmware site (VCDB shrink sql or so ..)
The question is, is there any verbose/debug flag, which I accidentally enabled time ago, so the DB is filling more rapidly? The VMs count did not change in the past and I did not change anything substantial in the infrastructure.
Or maybe everything is behaving alright and the SQL server should be upgraded ? (40 VMs)
ESXi 4.1 cluster Essentials Plus Appliances installed vDR, vMA
I am integrating UPS EATON with our ESXi 4.1 cluster. Eaton provides shutdown script for one particular ESXi host (shutdownESXi.pl) The problem was, after manual execution of shutdownESXi.pl script on vMA with
shutdownESXi.pl --server ServerName --username .. --password ..
the host was shut down but the VMs were migrated to another hosts (HA is enabled). BUT, what would happen if all the hosts would undergo the shutdown process ? I am afraid the VMs will start to migrate across the other ESXi hosts and it will never shut down properly.
1) Is there some other best-practice how to shutdown the cluster with the script on the vMA ? (disable HA firstly? maintenance mode?)
2) If someone integrated the Eaton shutdown script, is there any way how to hide the root pass within the Intelligent Power Protector ? It seems to be quite dumb to store it somewhere on the vMA in the plaintext..
I would really like to test VM monitoring, so if the VM locks up, vmware will restart it. I set the high sensitivity for VM monitoring for one particular virtual machine. I tried to:
1) Turn off vmware tools with /etc/init.d/...
2) Kill the vmware tools process
3) Run a fork bomb
The restart of the VM was not initiated at all. In the summary tab I have Vmware tools not running, but no action is made. Why? (it's vmware esxi with vcenter)
I have ou=People and there I have stored our employees. I have to somehow divide them to our current employees and former employees. What I was thinking about was to create 2 groups, ou=Employees,ou=People and ou=FormerEmployees,ou=People but changing the entryDN of the uid seems to be a bit tricky...
Should I rather add a custom attribute, or create some group? What is the best practice?
I have a problem with the ndbmtd process. When I use following configuration I expect both cores on our server with Intel(R) Pentium(R) CPU G6950 @ 2.80GHz will be fully utilized. Unfortunately this is not happening. Only core with id=0 is used. Second one has no load.
My configuration:
[ndbd default]
MaxNoOfExecutionThreads=2
[ndbd]
HostName=192.168.1.4
NodeId=3
LockExecuteThreadToCPU=0,1
LockMaintThreadsToCPU=0
mpstat -P ALL
08:47:09 AM CPU %user %nice %system %iowait %steal %idle
08:47:11 AM all 44.64 0.00 1.75 1.25 0.00 52.37
08:47:11 AM 0 89.45 0.00 1.01 2.01 0.00 7.54
08:47:11 AM 1 0.99 0.00 1.98 0.00 0.00 97.03
However, "top" shows 90% usage for ndbmtd process (why?)
My topology - 2 data nodes, ndb_mgmt in VM, mysqld in VM.
Is my CPU not capable of such thing, I have something misconfigured or mysql-cluster is not able to fully load multi-core processors?
We are using vmware Data Recovery appliance for backing up our virtual machine. I read the whole vDR Administration guide, but some of my questions are still unanswered.
1) If vDR appliance crashes, and I will have to install the new one and set the original destinations, will the vDR recognize the old backups?
2) I definitely quit backing up to CIFS share, as there were problems with mounting/unmouting the share lately, vDR was freezing as well. Are there any reasons why not to store the vDR VM backups directly on the host the vDR is running ? According to the Administration guide, this has better performance within vDR, but are there any major overall performance impacts on the host while making the backups in comparison with CIFS ? (waiting for I/O?)
I have XenServer non-paravirtualised VM and I want to convert them fro using in my ESXi infrastracture. Is it possible to do it with Essentials Plus pack ? What tool do I have to use?
Possible Duplicate:
Can you help me with my software licensing question?
We are thinking about getting the VMware essentials plus kit for 3 hosts, but in far future we would like to manage 4 hosts. Is there some cheaper way how to extend the license ? Or we have to buy the vCenter Standard with vSphere licenses ?
We're thinking about getting the vmware suite (VMware vSphere 4.1 Essentials Plus Kit). What I would like to know, if the vCenter Server is critical for High Availability feature.
1) Is cluster functional even if vCenter Server crashes? Are the VM protected in that case, or it fails completely?
2) Does the vCenter server have to be on same LAN ?
I have HP P2000 + XenServer solution working. What I'm thinking about is how to create LUNs for 20 virtual machines. Separate LUN for every VM ? It gives me ability to backup the specific virtual machine, however 20 vm = 20 shared storages in XenCenter and moreover I'm afraid of manageability of these LUNs or am I wrong ? Or I can have one bigger LUN for 20 VMs. What is the better option?
I set up remote LDAP server (Server1) and SSH with pam_ldap on Server2. Everything is working ok, I can login to SSH with LDAP credentials. But when I want to add new user, I have to firstly create it in LDAP databases and then run adduser on Server2.
How can I automatically create the user account on Server2 after adding it to LDAP database ? For example when the user first logs in? Thanks.