Xiong Chiamiov's questions

When updating a Kubernetes RollingUpdate deployment, kubectl get pods shows some of the pods spend a few minutes in the ContainerCreating state before moving to Running. Unfortunately, the official documentation on pod states doesn't include this as a documented state. Even the kubernetes codebase has only two mentions of the term, and neither has any sort of explanatory comment.

I've been doing some adjustments to the rolling update deployment configuration value (maxUnavailable and maxSurge) and the probe configuration (initialDelaySeconds), and I'm unsure if the container startup time that these values are affecting is part of ContainerCreating or another state.

To avoid having to parse X-Forwarded-For in Varnish, I'm trying to just set a header on the SSL terminator (currently Apache) that stores the direct client IP in a header.

On our development machine, this works:

RequestHeader set X-Foo %{REMOTE_ADDR}e

However, in staging it doesn't. Specifically, the header is empty, as illustrated by both varnishlog:

13 TxHeader     b X-Foo: (null)

(On the development machine, this shows the IP address as expected.)

Similarly, logging REMOTE_ADDR shows that it only appears to be populated on the dev machine:

# Config
LogFormat "%{X-Forwarded-For}i %{REMOTE_ADDR}e" combined
CustomLog "/var/log/httpd/access_log" combined

# Log file, staging
<my ip> -

# Log file, development
<my ip> <my ip>

Since the dev machine is, well, a dev machine, it is different in a number of ways; however, I can't track down which difference is causing this. The versions of Apache are the same (2.2.22), and I don't see anything relevant in any of the standard config files or /etc/sysconfig/httpd. And the rest of the system is reasonably similar, since they're built off the same CentOS 5 base image.

I can't even tell from the Apache documentation whether REMOTE_ADDR is expected to exist or not as an environment variable, but it clearly works on one machine, whether by fluke or design, and the inconsistency is driving me mad.

We're running multiple sites on the same hardware, and we'd like to serve them using the same pool of application machines. However, one site periodically gets greatly-increased traffic, and so we'd like to reserve a small section of machines for only the other sites.

Is it possible to do something like this in HAProxy?

backend foo
    server app00 0.0.0.0 cookie app00 check
    server app01 0.0.0.0 cookie app00 check
    server app02 0.0.0.0 cookie app00 check

backend bar
    server app03 0.0.0.0 cookie app03 check
    include foo

I realize that we could simply define the machines in multiple rules, but I'd rather avoid duplication if possible.

I need to add a line to a user's crontab file. Normally, I would do this with crontab -e, but I want to do it with a provisioning script.

Any clever methods?

I have 4 disks RAID-5ed to create md0, and another 4 disks RAID-5ed to create md1. These are then combined via LVM to create one partition.

There was a power outage while I was gone, and when I got back, it looked like one of the disks in md1 was out of sync - mdadm kept claiming that it only could find 3 of the 4 drives. The only thing I could do to get anything to happen was to use mdadm --create on those four disks, then let it rebuild the array. This seemed like a bad idea to me, but none of the stuff I had was critical (although it'd take a while to get it all back), and a thread somewhere claimed that this would fix things. If this trashed all of my data, then I suppose you can stop reading and just tell me that.

After waiting four hours for the array to rebuild, md1 looked fine (I guess), but the lvm was complaining about not being able to find a device with the correct UUID, presumably because md1 changed UUIDs. I used the pvcreate and vgcfgrestore commands as documented here. Attempting to run an lvchange -a y on it, however, gives me a resume ioctl failed message.

Is there any hope for me to recover my data, or have I completely mucked it up?

My LV was set up linearly. It seems that I should be able to recover at least the data from md0 by using something like TestDisk. However, examples show LVM partitions listed in TestDisk, while I only see sda,sdb,etc. and md0 and md1.

[$]> lvdisplay
  --- Logical volume ---
  LV Name                /dev/VolGroup/lvm
  VG Name                VolGroup
  LV UUID                b1h1VL-f11t-TGJv-ajbx-4Axn-wi89-fReUKu
  LV Write Access        read/write
  LV Status              suspended
  # open                 0
  LV Size                6.14 TiB
  Current LE             1609648
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:0

[$]> lvchange -ay /dev/VolGroup/lvm
  device-mapper: reload ioctl failed: Invalid argument