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Create LABEL for filesystems in Linux

Posted on by Bian Xi Leave a Comment on Create LABEL for filesystems in Linux

Create LABEL for filesystems in Linux

LABEL is used in /etc/fstab and system boot, such as cmdline.txt and grub, to allow the mounting identify the filesystem..

In order to allow system recognize the LABEL, blkid needs to show the filesystem has the LABEL.

Assign LABEL during filesystem creation

vfat

mkfs.vfat -n "label" /dev/XXX

ext4

mkfs.ext4 -L "label" /dev/XXX

btrfs

mkfs.btrfs -L "label" /dev/XXX

Change LABEL

LABEL can be changed after filesystem created.

swap

swaplabel -L "new label" /dev/XXX using util-linux

ext2/3/4

e2label /dev/XXX "new label" using e2fsprogs

btrfs

btrfs filesystem label /dev/XXX "new label" using btrfs-progs

reiserfs

reiserfstune -l "new label" /dev/XXX using reiserfsprogs

jfs

jfs_tune -L "new label" /dev/XXX using jfsutils

xfs

xfs_admin -L "new label" /dev/XXX using xfsprogs

fat/vfat

fatlabel /dev/XXX "new label" using dosfstools
mlabel -i /dev/XXX ::"new label" using mtools

exfat

tune.exfat -L "new label" /dev/XXX using exfatprogs
exfatlabel /dev/XXX "new label" using exfatprogs or exfat-utils

ntfs

ntfslabel /dev/XXX "new label" using ntfs-3g

udf

udflabel /dev/XXX "new label" using udftools

crypto_LUKS (LUKS2 only)

cryptsetup config --label="new label" /dev/XXX using cryptsetup

References

Persistent block device naming
How do I change the "label" reported by lsblk? [duplicate]

Change user name in ubuntu

Posted on by Bian Xi Leave a Comment on Change user name in ubuntu

Change user name in ubuntu

To change default user name ubuntu created in Raspberry Pi image, without adding a temporary user or enable root id, can be done using background job.

Commands

Change user name and home directory

usermod -l newUsername -d /home/newUsername oldUsername

Change group name

groupmod -n <newgroup> <oldgroup>

Job

The actual execution should be triggered as background job. I used screen command as below

  1. Login as ubuntu (default id)
  2. Run sudo -i to root
  3. Run screen to launch screen session
  4. Run following command, and press Ctrl-A d detach screen session immediately, without command executed.
newname=<new_user_name>
sleep 30; ps -ef | grep ^ubuntu | awk '{print $2}' | xargs kill -9 ; usermod -l $newname -d /home/$newname ubuntu; groupmod -n $newname ubuntu; mv /home/ubuntu /home/$newname
  1. Quit from console or ssh session
  2. After 30 seconds, login to the system using newname if succeeded. Othewise, use ubuntu login again.
  3. Then sudo to root and run screen -r to check if error or quit screen session.

References

How do I change my username?

Setup dnsmasq for DNS, DHCP and TFTP

Posted on by Bian Xi Leave a Comment on Setup dnsmasq for DNS, DHCP and TFTP

Setup dnsmasq for DNS, DHCP and TFTP

To setup DNS, DHCP and TFTP server using dnsmasq, need to consider them separately.

Environment

To ease of setup and backup, consider use docker container to run dnsmasq.

Configure macvlan

As DHCP server requires special network communication, macvlan can be used for this purpose.

Create macvlan on interface bond0 with IP address 192.168.1.250

docker network create -d macvlan -o parent=eth0 --subnet=192.168.1.0/24 --gateway=192.168.1.254 --ip-range=192.168.1.250/32 my_macvlan_250

Configure bridge macvlan

By default, the host machine who configured macvlan communicates with macvlan container, in such case, the DNS server running in dnsmasq will not be accessable by host machine.

In order to allow host machine also use DNS service running in macvlan, following configuration needs to be done, which creates another macvlan in host as bridge mode with IP address 192.168.1.249, and use it to access macvlan in docker with IP address 192.168.1.250.

Add following lines in /etc/network/interfaces

up ip link add my_macvlan_249 link eth0 type macvlan mode bridge
up ip addr add 192.168.1.249/32 dev my_macvlan_249
up ip link set my_macvlan_249 up
up ip route add 192.168.1.250/32 dev my_macvlan_249

Untested setup

Other setup likes using normal bridge network interface on physical network interface, I have tried it, so maybe it is also working.

Start container

Start container and map container /data folder to /app/dnsmasq/data, which can be used to save configuration files

docker run --name dnsmasq -d -it --restart unless-stopped -v /app/dnsmasq/data:/data --network my_macvlan_250 dnsmasq

Above command will run following command in container

dnsmasq -q -d --conf-file=/data/dnsmasq.conf --dhcp-broadcast

Troubleshooting dnsmasq

In order to debug dnsmasq, following command can be used.

docker logs -f dnsmasq

Due to so many requests on DNS from everywhere, if only want to debug DHCP service, following command can be used, and it filter out lines start with dnsmasq: .

docker logs -f dnsmasq --since 1m | grep -v -e "^dnsmasq: "

The DHCP log messages start with dnsmasq-dhcp: .

docker logs -f dnsmasq --since 1m | grep -e "^dnsmasq-dhcp: "

Note: As suggested in configuration, comment log-queries should disable logs for DNS too, but looks like useless.

#log-queries
log-dhcp

Configure TFTP boot

Configure TFTP server

Enable TFTP server

enable-tftp
tftp-root=/data/tftp

Configure DHCP boot

Sample configuration to select boot file according to option client-arch

dhcp-match=set:efi-x86_64,option:client-arch,7
dhcp-match=set:efi-x86_64,option:client-arch,9
dhcp-match=set:efi-x86,option:client-arch,6
dhcp-match=set:bios,option:client-arch,0
dhcp-boot=tag:efi-x86_64,efi64/syslinux.efi
dhcp-boot=tag:efi-x86,efi32/syslinux.efi
dhcp-boot=tag:bios,bios/lpxelinux.0

Actual configuration

dhcp-match=set:efi-x86_64,option:client-arch,7
dhcp-boot=tag:efi-x86_64,ipxe.efi
#dhcp-boot=tag:efi-x86_64,grubx64.efi

Set tag for iPXEBOOT, and configure ipxe options

# set tag to IPXEBOOT when has option 175
dhcp-match=IPXEBOOT,175
#dhcp-match=set:ipxe,175 # iPXE sends a 175 option.

dhcp-boot=tag:!IPXEBOOT,undionly.kpxe,dnsmasq,192.168.1.250
dhcp-boot=tag:IPXEBOOT,boot.ipxe,dnsmasq,192.168.1.250

# Configure iSCSI for ipxe boot
#dhcp-option=175,8:1:1
#dhcp-option=tag:IPXEBOOT,17,"iscsi:192.168.1.17::::iqn.2012-12.net.bx:ds1812.pxe-ubuntu"
#dhcp-option-force=vendor:175, 190, user
#dhcp-option-force=vendor:175, 191, password

Configure DHCP

DHCP global configuration, and set host using files in /data/hosts folder, and dhcp-host using files in /data/ethers folder.

no-hosts
hostsdir=/data/hosts
#addn-hosts=/data/banner_add_hosts
dhcp-hostsdir=/data/ethers
dhcp-leasefile=/data/dnsmasq.leases
expand-hosts
dhcp-option=44,192.168.1.250 # set netbios-over-TCP/IP nameserver(s) aka WINS server(s)
#dhcp-option=option:domain-search,bx.net,bianxi.com

DHCP Domain and rang

Following lines set up for dhcp hosts which are tagged as home

domain=bx.net,192.168.1.0/24
dhcp-range=tag:home,192.168.1.96,192.168.1.127,255.255.255.0,12h
dhcp-option=tag:home,option:router,192.168.1.254

DHCP mapping

To map MAC address to IP, tag, etc., use dhcp-host. Sample of mapping are shown below

dhcp-host=00:1b:77:07:08:af,set:home
dhcp-host=00:26:4a:18:82:c6,192.168.1.9,set:home
dhcp-host=win10,192.168.1.235,set:home

Note: contents in dhcp-host file, such as /etc/ethers should not have prefix of dhcp-host= as in main configuration file dnsmasq.conf does.

00:1b:77:07:08:af,set:home
00:26:4a:18:82:c6,192.168.1.9,set:guest
win10,192.168.1.235,set:home

DHCP reject unknown hosts

Using following configuration line to ignore all unknown hosts, so all hosts much registered using dhcp-host option.

dhcp-ignore=tag:!known

Guest domain

Another way to deal with unknown hosts is to setup guest network.

Following lines define a DHCP services for hosts without tag home

dhcp-range=tag:!home,192.168.1.128,192.168.1.143,255.255.255.0,4h
dhcp-option=tag:!home,option:router,192.168.1.254
dhcp-option=tag:!home,option:domain-name,guest.net
#dhcp-option=tag:!home,option:domain-search,guest.net

Another way is to define guest network range as below for those hosts with tag guest.

#domain=guest.net,192.168.1.0/24
#dhcp-range=tag:guest,192.168.1.128,192.168.1.143,255.255.255.0,4h
#dhcp-option=tag:guest,option:router,192.168.1.254

#dhcp-host=00:a0:98:5f:9e:81,set:guest

DHCP mapping consideration

The logic of DHCP tags is described below

  • Host request DHCP, then it has one tag, which is interface name, such as eth0

  • If it is mapped with one dhcp-host line, they will be tagged as known

  • Tags can be given by various ways

    • Set in dhcp-host line. For example, set guest in following line
    dhcp-host=00:a0:98:5f:9e:81,set:guest
    • Set by IP range
    dhcp-range=set:red,192.168.0.50,192.168.0.150
    • Set by host matching
    dhcp-vendorclass=set:red,Linux
dhcp-userclass=set:red,accounts
dhcp-mac=set:red,00:60:8C:*:*:*

  • Tags can be used by various ways

    • Used in IP range
    dhcp-range=tag:green,192.168.0.50,192.168.0.150,12h

  • Tags can be used in not condition

    dhcp-option=tag:!home,option:router,192.168.1.254

DHCP options

DHCP options and their numbers, can be found in DHCP log, such as below.

dnsmasq-dhcp: 2177430021 available DHCP range: 192.168.1.96 -- 192.168.1.127
dnsmasq-dhcp: 2177430021 available DHCP range: 192.168.1.128 -- 192.168.1.143
dnsmasq-dhcp: 2177430021 vendor class: MSFT 5.0
dnsmasq-dhcp: 2177430021 client provides name: baidu-windows
dnsmasq-dhcp: 2177430021 DHCPREQUEST(eth0) 192.168.1.113 00:a0:98:1d:b0:fc 
dnsmasq-dhcp: 2177430021 tags: home, known, eth0
dnsmasq-dhcp: 2177430021 DHCPACK(eth0) 192.168.1.113 00:a0:98:1d:b0:fc baidu-windows
dnsmasq-dhcp: 2177430021 requested options: 1:netmask, 3:router, 6:dns-server, 15:domain-name, 
dnsmasq-dhcp: 2177430021 requested options: 31:router-discovery, 33:static-route, 43:vendor-encap, 
dnsmasq-dhcp: 2177430021 requested options: 44:netbios-ns, 46:netbios-nodetype, 47:netbios-scope, 
dnsmasq-dhcp: 2177430021 requested options: 119:domain-search, 121:classless-static-route, 
dnsmasq-dhcp: 2177430021 requested options: 249, 252
dnsmasq-dhcp: 2177430021 bootfile name: undionly.kpxe
dnsmasq-dhcp: 2177430021 server name: dnsmasq
dnsmasq-dhcp: 2177430021 next server: 192.168.1.250
dnsmasq-dhcp: 2177430021 broadcast response
dnsmasq-dhcp: 2177430021 sent size:  1 option: 53 message-type  5
dnsmasq-dhcp: 2177430021 sent size:  4 option: 54 server-identifier  192.168.1.250
dnsmasq-dhcp: 2177430021 sent size:  4 option: 51 lease-time  12h
dnsmasq-dhcp: 2177430021 sent size:  4 option: 58 T1  6h
dnsmasq-dhcp: 2177430021 sent size:  4 option: 59 T2  10h30m
dnsmasq-dhcp: 2177430021 sent size:  4 option:  1 netmask  255.255.255.0
dnsmasq-dhcp: 2177430021 sent size:  4 option: 28 broadcast  192.168.1.255
dnsmasq-dhcp: 2177430021 sent size:  6 option: 15 domain-name  bx.net
dnsmasq-dhcp: 2177430021 sent size: 23 option: 81 FQDN  03:ff:ff:62:61:69:64:75:2d:77:69:6e:64:6f...
dnsmasq-dhcp: 2177430021 sent size:  4 option:  6 dns-server  192.168.1.250
dnsmasq-dhcp: 2177430021 sent size:  4 option:  3 router  192.168.1.254
dnsmasq-dhcp: 2177430021 sent size:  4 option: 44 netbios-ns  192.168.1.250

Configure DNS

Set up link DNS server

# DNS Server
server=165.21.83.88
#server=165.21.100.88
server=8.8.8.8

DNS mapping

DNS entries are defined as the format of /etc/host file

192.168.1.1     host1 host-alias

Sample configuration steps

Add a static IP entry for a known mac address

In ethers file, add following entry for DHCP

44:55:66:77:88:99,192.168.1.222,set:home

In banner_add_hosts file add following entry for DNS

192.168.1.222    cat

Overlay Filesystem Basic

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Overlay Filesystem Basic

Overlay filesystem merges lower and upper directories into merged directory.

Mount writable

mount -t overlay overlay -o lowerdir=/lower1:/lower2:/lower3,upperdir=/upper,workdir=/work /merged

The above example will have the order:

/upper
/lower1
/lower2
/lower3

  • The lower directory can be read-only or could be an overlay itself.
  • The upper directory is normally writable.
  • The work directory is used to prepare files as they are switched between the layers, it needs to be an empty directory on the same filesystem mount as the upper directory.
  • All changes in the merged directory are still reflected in upper.
  • New files created in lower and upper will be shown in merged.
  • All files before opened directory, the content is still mapped according to layer.
  • All files after opened in merged directory, the content will not be reflected in merged directory.

Mount read-only

To mount as read only, no upper and work directory are required.

mount -t overlay overlay -o lowerdir=/lower1:/lower2 /merged

Whiteout files

Whiteout is to simulate a file removed from upper layer directory. It is created as a character device with 0/0 device number.

Opaque directories

Opaque is to simulate a directory removed from upper layer directory. It is made by setting the xattr “trusted.overlay.opaque” to “y”.

References

Overlay filesystem
Overlay Filesystem
Explaining OverlayFS – What it Does and How it Works

Placing fingers for FPS gaming

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Placing fingers for FPS gaming

Frames per second (FPS) gaming requires muscle memory, fast response is not only needs for screen, but also for player, there is no time to move eyes from screen to hands at all.

Keyboard

Place fingers correctly while gaming can take advantage, such as fast response, less mistake, less stress, etc. Following placement just a guide for some games, such as genshin impact, etc.

  • Middle finger on W and alternate it between S
  • Index finger on D
  • Ring finger on A
  • Pinky finger on shift alternating to Ctrl when needing to crouch
  • Thumb finger over space alternating to C/X/Z for the commands

If you put keyboard flat, you may able to use the palm near to your pinky finger to hit control. In this case, you need to use Middle/Index/Ring to hit C/X/Z, anyway, thumb is not easy to reach them as well.

Controller

Most of buttons and sticks are very obvious, except bumpers and triggers.

  • Index finger on bumper
  • Middle finger on trigger

Xbox Series X|S Wireless Controller

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Xbox Series X|S Wireless Controller

The Xbox Series X|S wireless controller works with Xbox One, Windows 10, and cloud gaming devices.

Layout

N Name N Name
1 Left stick 10 Expansion port
2 Left bumper 11 Right stick
3 View button 12 Left trigger
4 Xbox button 13 USB-C power port
5 Share button X X button
6 Menu button Y Y button
7 Right bumper A A button
8 Directional pad (D-pad) B B button
9 3.5-mm port

References

Get to know your Xbox Series X|S Wireless Controller

Btrfs Basic

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Btrfs Basic

Status

btrfs device states /app
btrfs fi show /app

Convert raid

Convert to raid0 and remove one disk

btrfs balance start -f -sconvert=single -mconvert=single -dconvert=single /app
btrfs device remove /dev/bcache0 /app

Add disk and convert to raid1

btrfs device add -f /dev/bcache0 /app
btrfs balance start -dconvert=raid1 -mconvert=raid1 /app

Check raid level

# btrfs fi df /app
Data, RAID1: total=2.69GiB, used=2.51GiB
System, RAID1: total=32.00MiB, used=16.00KiB
Metadata, RAID1: total=317.94MiB, used=239.55MiB
GlobalReserve, single: total=12.03MiB, used=0.00B
#

If contains multiple block group profiles, could happen when a profile conversion using balance filters was interrupted.

Data, RAID1: total=2.03GiB, used=1.86GiB
Data, single: total=704.00MiB, used=665.56MiB
System, RAID1: total=32.00MiB, used=16.00KiB
Metadata, RAID1: total=288.00MiB, used=239.56MiB
GlobalReserve, single: total=11.94MiB, used=0.00B
WARNING: Multiple block group profiles detected, see 'man btrfs(5)'.
WARNING:   Data: single, raid1

Perform rebalance again

# btrfs balance start -dconvert=raid1 -mconvert=raid1 /app
Done, had to relocate 12 out of 12 chunks

Scrub

btrfs scrub start /app
btrfs scrub status /app

Error

To correct error, first find out corrupted file, then restore from backup or delete the file

dmesg -T | grep BTRFS | grep 'check error' | grep path

Then reset error count to zero

btrfs device states -z /app

Then scrub again.

References

BTRFS-MAN(5)

Snap Basic

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Snap Basic

To check the snap utility version, you need to use snap --version command as shown below.

Basic Commands

snap install <snap_name>
snap remove <snap_name>
snap remove <snap_name> --purge       # No snapshot generated
snap list
snap list --all
snap info <snap_name>
snap find <snap_name>
snap revert <snap_name>
snap enable <snap_name>
snap disable <snap_name>
snap download <snap_name>

Snap updates

snap refresh <snap_name>
snap refresh --list

Snap Channels (releases)

They are stable, edge, beta and candidate.

# snap install --edge <snap_name>
# snap install --beta <snap_name>
# snap install --candidate <snap_name>

Snap Changes

snap changes

Snap Connections

snap connections <snap_name>

Snap Model/Version

snap model
snap --version

Snap Service

snap services lxd
snap restart lxd
snap stop lxd
snap start lxd
snap logs lxd

Snap Alias

snap alias <snap_name> <alias_name>
snap aliases
snap unalias <alias_name>

Snap Snapshot

snap save
snap check-snapshot <snapshot_num>
snap restore <snapshot_num>
snap forget <snapshot_num>        # Delete a snapshot
snap saved
snap saved --id=<snapshot_num>        # View a snapshot

Snap login

snap login
snap logout

Snap Config

snap set system refresh.retain=2
snap get system refresh.retain
snap unset system refresh.retain

References

36 Popular Snap command examples in Linux for Beginners

VIM Basic

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VIM Basic

This is not a full guide, but those new functions to me.

Movement

Scrolling

^E - down (End)
^Y - up (Hard to remember and use)

Jumping

H - High (Top)
M - Middle
L - Low (Bottom)

Object

w - words
s - sentences
p - paragraphs
t - tags (in XML/HTML file)

Selection

a -- all (whole + border)
i - in (whole)
t - 'til (find but no border)
f - find
F - find backword

Command

d y v
c i a o

Basic Example

diw
caw
yi)
va"

Macro

Register

q{key}
...
q

Play

@{key}

Register

View

:reg

Paste with number 

"<n>p

Plugins

vundle - plugin manager
nerdtree - file drawer
ctrlp - fuzzy file finder
fugitive - git tool
syntastic - systax checker / linter

References

nicknisi / vim-workshop