thuandt

Installing XenServer 6.2.0 from a USB Stick

• Download the XenServer 6.2.0 ISO image

• Format a USB stick using FAT32.

• Use unetbootin to install the ISO to the USB stick. Use the “DiskImage” option instead of the “Distribution” one, and point it right to the ISO file.

• Now we need to fix up some boot stuff (All paths are relative to the root of the USB drive)

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/* Disable "List all Tabs" Button */
.tabs-alltabs-button {
display: none !important;
}

/* Disable Container box for "List all Tabs" Button */
.tabs-alltabs-box {
display: none !important;
}

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Keybase proof

I hereby claim:

• I am thuandt on github.
• I am thuandt (https://keybase.io/thuandt) on keybase.
• I have a public key ASAOXz-V0iQWVO2CXIGKgcuhu_js3JzwICItI0Szy2unOAo

To claim this, I am signing this object:

thuandt

RAID-Z

The strongest valid recommendation based on exact fitting of blocks into stripes is the following: If you are using RAID-Z with 512-byte sector devices with recordsize=4K or 8K and compression=off (but you probably want compression=lz4): use at least 5 disks with RAIDZ1; use at least 6 disks with RAIDZ2; and use at least 11 disks with RAIDZ3.

To summarize: Use RAID-Z. Not too wide. Enable compression.

thuandt

thuandt

Types

A type is a collection of possible values. An integer can have values 0, 1, 2, 3, etc.; a boolean can have values true and false. We can imagine any type we like: for example, a HighFive type that allows the values "hi" or 5, but nothing else. It's not a string and it's not an integer; it's its own, separate type.

Statically typed languages constrain variables' types: the programming language might know, for example, that x is an Integer. In that case, the programmer isn't allowed to say x = true; that would be an invalid program. The compiler will refuse to compile it, so we can't even run it.

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GCP & GKE setup

$ gcloud auth application-default login
$ gcloud config set core/project ${GCP_PROJECT}
$ gcloud config set core/account ${SERVICE_ACCOUNT}
$ gcloud config set compute/region ${REGION}
$ gcloud config set compute/zone ${ZONE}
$ gcloud config set container/cluster ${CLUSTER_NAME}
# gcloud config set container/use_client_certificate True

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Random delay for cron.daily, cron.weekly, cron.monthly

Source

Wouldn’t it be nice if cron’s daily, weekly and monthly jobs could be run with a slight offset? At least that’s what I thought when 20+ servers were hitting my backup infrastructure at once. The scripts in /etc/cron.daily, /etc/cron.weekly and /etc/cron.monthly are triggered directly from crontab at fixed times. Here’s what /etc/crontab looks like in Ubuntu Server 16.04:

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# List unique values in a DataFrame column
# h/t @makmanalp for the updated syntax!
df['Column Name'].unique()

# Convert Series datatype to numeric (will error if column has non-numeric values)
# h/t @makmanalp
pd.to_numeric(df['Column Name'])

# Convert Series datatype to numeric, changing non-numeric values to NaN
# h/t @makmanalp for the updated syntax!

thuandt

Requirements

• no upfront installation/agents on remote/slave machines - ssh should be enough
• application components should use third-party software, e.g. HDFS, Spark's cluster, deployed separately
• configuration templating
• environment requires/asserts, i.e. we need a JVM in a given version before doing deployment
• deployment process run from Jenkins

Solution