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Linux Systems Guides

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rick
wrote on last edited by rick

#1
Many times you need to know what version and or distribution of linux is running. The command varies
```
lsb_release -a
```
Example:
```
No LSB modules are available.
Distributor ID:	Debian
Description:	Debian GNU/Linux 8.10 (jessie)
Release:	8.10
Codename:	jessie
```
```
cat /etc/lsb_release
```
```
cat /etc/debian_version
```
```
8.10
```
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R Offline
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rick
wrote on last edited by rick

#2
Find centOS version:
```
cat /etc/centos-release
```
RHEL:
```
cat /etc/redhat-release
```
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FreeBSD Notes

R
rick

Unable to negotiate with 10.10.1.35 port 22: no matching host key type found. Their offer: ssh-rsa,ssh-dss
While attempting ssh this error is generally due to mismatched versions of ssh, where an up to date version is attempting to access an older version

Add the following to your command :

The proper way:
ssh -o KexAlgorithms=diffie-hellman-group14-sha1 -oHostKeyAlgorithms=+ssh-dss 10.10.1.35
The cheap way:

Example :
ssh -oHostKeyAlgorithms=+ssh-dss 10.10.1.35
or ssh -oHostKeyAlgorithms=+ssh-dss user@10.10.1.35

This can be added to the ~/.ssh/config file
Host my-server HostName 10.10.1.35 HostKeyAlgorithms=+ssh-dss

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R
rick

Locate hard drive and get information
ls -l /sys/block | grep sd.
Output:
lrwxrwxrwx 1 root root 0 Jun 22 06:28 sda -> ../devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdb -> ../devices/pci0000:00/0000:00:1f.2/ata2/host1/target1:0:0/1:0:0:0/block/sdb lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdc -> ../devices/pci0000:00/0000:00:1f.2/ata3/host2/target2:0:0/2:0:0:0/block/sdc lrwxrwxrwx 1 root root 0 Jun 22 06:28 sdd -> ../devices/pci0000:00/0000:00:1f.2/ata4/host3/target3:0:0/3:0:0:0/block/sdd
Or for a more detailed view
strace -e trace=open lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINTS sda 8:0 0 3.6T 0 disk ├─data--2-data--2_tmeta 252:3 0 15.9G 0 lvm │ └─data--2-data--2-tpool 252:9 0 3.6T 0 lvm │ ├─data--2-data--2 252:10 0 3.6T 1 lvm │ ├─data--2-vm--101--disk--0 252:11 0 8G 0 lvm │ ├─data--2-vm--103--disk--0 252:12 0 32G 0 lvm │ ├─data--2-vm--107--disk--0 252:13 0 500G 0 lvm │ └─data--2-vm--108--disk--0 252:20 0 100G 0 lvm └─data--2-data--2_tdata 252:6 0 3.6T 0 lvm └─data--2-data--2-tpool 252:9 0 3.6T 0 lvm ├─data--2-data--2 252:10 0 3.6T 1 lvm ├─data--2-vm--101--disk--0 252:11 0 8G 0 lvm ├─data--2-vm--103--disk--0 252:12 0 32G 0 lvm ├─data--2-vm--107--disk--0 252:13 0 500G 0 lvm └─data--2-vm--108--disk--0 252:20 0 100G 0 lvm sdb 8:16 0 698.6G 0 disk └─sdb1 8:17 0 698.6G 0 part /mnt/pve/backups sdc 8:32 0 3.6T 0 disk ├─vm--data-vm--data_tmeta 252:4 0 15.9G 0 lvm │ └─vm--data-vm--data-tpool 252:14 0 3.6T 0 lvm │ ├─vm--data-vm--data 252:15 0 3.6T 1 lvm │ ├─vm--data-vm--100--disk--0 252:16 0 270G 0 lvm │ ├─vm--data-vm--102--disk--0 252:17 0 100G 0 lvm │ ├─vm--data-vm--104--disk--0 252:18 0 25G 0 lvm │ └─vm--data-vm--106--disk--0 252:19 0 32G 0 lvm └─vm--data-vm--data_tdata 252:7 0 3.6T 0 lvm └─vm--data-vm--data-tpool 252:14 0 3.6T 0 lvm ├─vm--data-vm--data 252:15 0 3.6T 1 lvm ├─vm--data-vm--100--disk--0 252:16 0 270G 0 lvm ├─vm--data-vm--102--disk--0 252:17 0 100G 0 lvm ├─vm--data-vm--104--disk--0 252:18 0 25G 0 lvm └─vm--data-vm--106--disk--0 252:19 0 32G 0 lvm sdd 8:48 0 931.5G 0 disk ├─sdd1 8:49 0 1007K 0 part ├─sdd2 8:50 0 1G 0 part └─sdd3 8:51 0 930.5G 0 part ├─pve-swap 252:0 0 8G 0 lvm [SWAP] ├─pve-root 252:1 0 96G 0 lvm / ├─pve-data_tmeta 252:2 0 8.1G 0 lvm │ └─pve-data 252:8 0 794.3G 0 lvm └─pve-data_tdata 252:5 0 794.3G 0 lvm └─pve-data 252:8 0 794.3G 0 lvm +++ exited with 0 +++ cat /proc/partitions major minor #blocks name 8 0 3907018584 sda 8 16 732574584 sdb 8 17 732572672 sdb1 8 32 3907018584 sdc 8 48 976762584 sdd 8 49 1007 sdd1 8 50 1048576 sdd2 8 51 975712967 sdd3 252 0 8388608 dm-0 252 1 100663296 dm-1 252 2 8495104 dm-2 252 3 16650240 dm-3 252 4 16650240 dm-4 252 6 3873329152 dm-6 252 5 832888832 dm-5 252 7 3873329152 dm-7 252 8 832888832 dm-8 252 9 3873329152 dm-9 252 10 3873329152 dm-10 252 11 8388608 dm-11 252 12 33554432 dm-12 252 13 524288000 dm-13 252 14 3873329152 dm-14 252 15 3873329152 dm-15 252 16 283115520 dm-16 252 17 104857600 dm-17 252 18 26214400 dm-18 252 19 33554432 dm-19 252 20 104857600 dm-20
Locate drive by serial and model information
hdparm -i /dev/sda /dev/sda: Model=WDC WD4000FYYZ-05UL1B0, FwRev=00.0NS05, SerialNo=WD-WCC132262513 Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq } RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=0 BuffType=unknown, BuffSize=unknown, MaxMultSect=16, MultSect=off CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=7814037168 IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120} PIO modes: pio0 pio3 pio4 DMA modes: mdma0 mdma1 mdma2 UDMA modes: udma0 udma1 udma2 udma3 udma4 udma5 *udma6 AdvancedPM=yes: unknown setting WriteCache=disabled Drive conforms to: Unspecified: ATA/ATAPI-1,2,3,4,5,6,7 * signifies the current active mode

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R
rick

Screen recording can use webm as their format, it can be more simple to use a gif to embed into a website or forum, than adding scripts to host different video format.

In this case I grabbed a screen record of the progress for writing zeros to a hard drive with dd

Use ffmpeg to convert webm to gif:

First create a pallet:

Move into the directory which the webm is located, or type in the path

Where ‘dd.webm’ is the screen recording
ffmpeg -y -i dd.webm -vf palettegen palette.png
Output:

Then convert the webm to gif:
ffmpeg -y -i dd.webm -i palette.png -filter_complex paletteuse -r 10 dd.gif

This is what I ended up with, looks like any image of any alien on the interwebz, as if shot through a potato, some tweaking of the command is in my future. None the less.

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rick

Write zeros to all sectors

Use the command ‘lsblk’ to find the drive you wish to erase

I’m using ‘dd’ to erase things

In this case I’m torching sdb

Only use status=progress if you care it’s not necessary
dd if=/dev/zero of=/dev/sdb bs=12M status=progress

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R
rick

Remove old kernel images that are cluttering the system

Most of these errors are due to low or not enough space left in the root partition.

If you are using a Debian flavor:
sudo apt-get autoremove --purge

Inform grub whenever an old kernel is removed:
update-grub

Remove the un-used kernel config files:

These will be the files pre cursed as ‘rc’ where installed kernels use ‘ii’

… As well as files no longer used or required due to dependencies

This command will detect, print, and remove left over cruft from previously installed packages or scripts, that have been removed or updated.
sudo dpkg --purge $(dpkg -l | awk '/^rc/{print $2}')

You can re-run the following to view the installed kernel(s):
dpkg --list | grep linux-image

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