Linux, FreeBSD, Juniper, Cisco / Network security articles and troubleshooting guides

**Posted:** Fri Sep 15, 2017 2:14 am

When FreeBSD runs as a Guest Operating System in Vmware ESXi or other hypervisor, disks can be hot added (without powering off the system).

List available disk in FreeBSD.

Code:

$ sudo camcontrol devlist
<NECVMWar VMware IDE CDR10 1.00>   at scbus1 target 0 lun 0 (cd0,pass0)
<VMware Virtual disk 1.0>          at scbus2 target 0 lun 0 (da0,pass1)
<VMware Virtual disk 1.0>          at scbus2 target 1 lun 0 (da1,pass2)

After new disk has been added to the ...

**Posted:** Tue Jun 14, 2016 10:51 am

There are multiple RAID solutions out there and I prefer a server with hardware raid, but for convenience I recommend friends to use a commercial solution like the Seagate 2Bay NAS enclosure.

Interesting about this NAS is that it is using Linux RAID and sometimes the RAID container fails (configuration lost due to hard reset or other reasons that Seagate has failed to document).

In such cases, the storage array requests that it be reconfigured ...

**Posted:** Mon Mar 03, 2014 9:47 am

Many utilities are out there to measure I/O throughput statistics on disk. FreeBSD has a tool named "gstat". Man gstat:

Quote:

GSTAT(8) FreeBSD System Manager's Manual GSTAT(8)

NAME
gstat -- print statistics about GEOM disks

SYNOPSIS
gstat

DESCRIPTION
The gstat utility can be used to monitor I/O transactions of geom(4)
devices.

The options are as follows:

-a Only display providers that are at least 0.1% busy.

-b Batch mode. Collect numbers, ...

**Posted:** Fri Feb 28, 2014 6:35 pm

Use "blkid" utility to read filesystem UUIDs.

Mqn blkid:

Quote:

BLKID(8) System Administration BLKID(8)

NAME
blkid - locate/print block device attributes

SYNOPSIS
blkid -L label | -U uuid

blkid

blkid -p
device ...

blkid -i device ...

DESCRIPTION
The blkid program is the command-line interface to working ...

**Posted:** Sat Feb 15, 2014 4:39 pm

When FreeBSD fsck starts, it checks /etc/fstab file for the given filesystem type. If the filesystem entry is commented out, fsck will show the following error:

Code:

# fsck -y /dev/twed1s1
fsck: Could not determine filesystem type
# grep twed1s1 /etc/fstab
#/dev/twed1s1 /store2                    ufs     rw  2  2

Uncomment the line and fsck will detect the ufs type.

Obviously, there are other solutions, like specifying "-t ufs" flag, but in some situations this can fix a ...

**Posted:** Wed Feb 05, 2014 12:16 pm

Existing mounted filesystems and their options.

To remount an already mounted filesystem without unmounting it (in Linux world) is changing mount options in FreeBSD world.
Quote "man mount":

Quote:

-u The -u flag indicates that the status of an already mounted file
system should be changed. Any of the options discussed above
(the -o option) may be changed; also a file system can be changed
from read-only to read-write or vice versa. An attempt to ...

**Posted:** Wed Jan 29, 2014 6:57 am

From 'man lvcreate':

Quote:

lvcreate [-l|--extents LogicalExtentsNumber[%{VG|FREE|ORIGIN}

Below is a command to create a logical volume that spans the whole free space in the VolumeGroup
# vgs
VG #PV #LV #SN Attr VSize VFree
rootVG 1 2 0 wz--n- 20.00g 0
vmVG 1 0 0 wz--n- 128.81g 128.81g
# lvs
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
rootLV rootVG -wi-ao---- 18.55g
swapLV rootVG -wi-ao---- 1.44g

# lvcreate vmVG -n vmLV -l 100%FREE ...

**Posted:** Tue May 18, 2010 9:52 am

So, you created an array and you messed up something? Now you would like to delete it?
Please note: all data will be lost with this operation!

1. Stop the array

Code:

# mdadm -S /dev/md0

2. Remove the disks from the array (in my example md0 is a raid5 array with 3 disks)

Code:

# mdadm /dev/md0 -r /dev/sda
# mdadm /dev/md0 -r /dev/sdb
# mdadm /dev/md0 -r /dev/sdc

3. Destroy the array configuration from each ...

**Posted:** Mon May 17, 2010 6:08 pm

I'm not going to explain what a software RAID is. There is google for this.
However, i will try to summarize here how to remove a failed disk and add a new one instead of it. Follow the steps and ask if somethig failes...

1. Set the drive (in my example /dev/sda) as faulty

Code:

# mdadm --manage --set-faulty /dev/md0 /dev/sda

2. Remove the faulty disk from the array

Code:

# mdadm /dev/md0 -r /dev/sda

3. Stop ...

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