Here I document the Linux commands I use most often for fast pickup then needed.
(Many years ago I liked to call myself a console cowboy, however without continous Linux work I am no more the Linux Fu Master I newer really were and have now resorted to creating an ad-hoc cheat sheet)
System :
shell> lsb_release -a : shows Ubuntu version and codename.
shell> ubuntu-support-status : show support status of packages (most packages will be supported according to end-of-life of current release version).
shell> egrep -c ' lm ' /proc/cpuinfo : shows whether CPU is 64 bit
0: not 64 bit
1 or more : 64 bit
shell> uname -m : shows whether the kernel is running 64 bit
i386 or i486 or i586 or i686 : 32 bit kernel
x86_64 : 64 bit kernel
shell> uname -v : shows kernel version, which is related to release version.
shell> uname -a : shows all the info about the kernel (hostname, release date, architecture, name, version, OS)
shell> lscpu : shows cores, threads per core and other cpu properties
shell> nproc : number of processing units (threads)
shell> fdisk -l : list all the physical disks, their partitions and their mounts
shell> dmesg | less : scroll through dmesg one page at a time
Package management
Repositories : local index of available packages for Ubuntu, the index is divided into 5 sections:
Main : all packages are free, open & supported by Ubuntu, that is: Ubuntu provides fixes and security updates (until the installed version of Ubuntu reached end-of-life)
Universe : free & open and managed by the community. Ubuntu does NOT support these packages.
Multiverse : software packages that are not both open & free. This index is NOT enabled by default.
Restricted : proprietary drivers.
Partner : proprietary packages by partners (eg. earlier Skype was distributed through this index).
/etc/apt/sources.list :
shell> add-apt-repository universe : enable the Universe index (remember to update it after enabling it).
shell> add-apt-repository -r universe : disable the Universe index.
shell> apt-get update : updates the local index of packages.
shell> apt-get upgrade : upgrade all installed packages to the newest version (the newest version according to the repositories)
shell> do-release-upgrade : upgrade from current version to next version, eg. from 12.04 to 14.04. It is NOT possible to specify what version to upgrade to - it will simply be the next version. I think if having LTS, then the next version will be the next LTS version.
shell> do-release-upgrade -c : display what the next release version will be.
shell> dpkg -l : list all packages installed
shell> dpkg -l | grep virt : list all packages that have "virt" in name or description
shell> apt-get update : up
Disk management
shell> fdisk -l : list all the physical disks, their partitions and their mounts including non-mounted.
shell> cat /etc/fstab : list all media that are supposed to be mounted.
shell> cat /etc/mtab : list all media that are actually mounted.
shell> cat /proc/mounts | grep /dev/sd : short list all mounted media.
shell> mount : list all mounted filesystems with labels.
shell> mount | grep /dev/sd : short list all mounted media.
shell> mount -l : seems to be identical to mount.
shell> mount -a : mount all mount points defined in /etc/fstab.
shell> mount -t vfat /dev/sdd1 /media/USB : mount a FAT32 partition (d drive partition 1) to the /media/USB mount point.
shell> mount -t ntfs-3g /dev/sdd1 /media/USB : mount an NTFS partition.
should use fdisk -l first to identify the device (eg. maybe not /dev/sdd1)
shell> umount /media/USB : unmount any device from the /media/USB mount point.
shell> dmesg | grep mount : see the mounts as they happened through boot.
shell> mkfs.ntfs /dev/sde1 : format partition sde1 to NTFS
shell> mkfs.ntfs -f /dev/sde1 : fast format (no "Initializing device with zeroes" and no checking of bad sectors)
mkfs.ext4
mkfs.vfat
mkfs.exfat
shell> df : disk space usage on all mounted filesystems.
shell> df -l : list only local filesystems (df will include external filesystems)
shell> df -h : human readable.
shell> df --total -h : print a total row at the last line.
shell> df --o -h : include all fields in list of mounted filesystems.
shell> df -aTh : list all mounts and what they are mounted on.
shell> df /dev/sda : disk usage for individual disk.
shell> df /dev/sda1 : disk usage for individual partition.
shell> df -t ext4 : show all ext4 filesystems
shell> df -h /media/cdrom : show what disk & partition a specific folder belongs to.
shell> findmnt : find all mounted filesystems.
shell> findmnt -t ext4 : show only filesystems of type ext4.
shell> findmnt -s : list fstab content.
shell> findmnt --fstab --evaluate : convert uuid to device name.
shell> du : disk usage : traverses current folder recursevely and report folder sizes
du -h --max-dept=1 : reports folder sizes for current sub-folders.
du -h --max-dept=1 | sort -n : sort folders after size.
du -hs : (s : summarize) : current folder size.
du -hs /var/* : size of all sub-folders of /var.
File management
shell> ls -l : list view of current directory.
shell> df -h : show used & available disk space.
shell> scp sourcefile targetDestination : copy a file from one server to another server (destination does NOT contain the filename)
shell> scp root@123.123.123.123:/var/VMs/VHDs/MySql . : copy the MySql VM from a server with IP 123.123.123.123 using the root user (on 123.123.123.123) to current directory (current directory is referenced using a dot '.')
shell> scp MySql root@123.123.123.123:/var/VMs/VHDs : copy the Mysql file from current directly to the /var/VMs/VHDs directory on server with IP 123.123.123.123 using the root user on 123.123.123.123.
shell> cp filename1 filename2 : copy filename1 to filename2
shell> chown user:group filename : sets user & group for a specific file
shell> rm filename : deletes the file
shell> mv filename1filename2 : rename filename1 to filename2
Volume management
LVM : Logical Volume Manager (I have installed on fhOic)
shell> df -h : shows hdd usage
/dev/mapper/ubuntu--vg-ubuntu--lv : 98G
shell> vgdisplay : shows volume groups and how much space is used and how much is free.
shell> vgdisplay ubuntu-vg : shows volume group named ubuntu-vg.
lvextend -L +49.4G /dev/mapper/ubuntu--vg-ubuntu--lv : extends that volume with 49.4GB, however it will not yet show up in df -h
resize2fs /dev/mapper/ubuntu--vg-ubuntu--lv : update the filesystem on that volume - it will now show up in df -h.
User management
sudo passwd root : start interactive prompt for giving root a password
su - : switch user to root.
Enable SSH for root user
shell> nano /etc/ssh/sshd_config :
change : #PermitRootLogin prohibit-password
to : PermitRootLogin yes
shell> systemctl restart ssh : restart ssh service
Network
shell> ip a : display interface information.
shell> nano /etc/netplan/00-installer-config.yaml : edit the interface configuration file.
network:
version: 2
ethernets:
enp1s0:
addresses: [202.183.164.145/25]
gateway: 202.183.164.254
nameservers:
addresses: [203.146.237.237, 8.8.8.8]
shell> netplan try : if there are no errors press enter otherwise wait for timer to revert.
shell> netplan apply : make the changes permanent.
shell> reboot : I don't think this is necessary.
Ubuntu 12
shell> ifconfig : display interface information.
shell> nano /etc/network/interfaces : edit the interface configuration file.
/etc/bind/named.conf : specifies which other configuration files to use, typically :
/etc/bind/named.conf.options : dns options like whether to listen to v6 etc.
/etc/bind/named.conf.default-zones : default zones such as localhost, its reverse and the root hints.
/etc/bind/named.conf.local : references to local zone files (in the same /etc/bind/ directory).
Roles
primary server : bind9 reads the data for a zone from a file on its host and is authoritative for that zone
secondary server : bind9 gets the zone data from a nameserver that is authoritative for the zone.
caching server : bind9 will find the answer to name queries and remember the answer when the domain is queried again. I think that if you do NOT make your bind9 a caching server, then it will NOT be able to answer on requests other than the domains for which bind9 is either a primary or secondary server. To make bind9 act as a caching server uncomment forwarders in /etc/bind/named.conf.options and set one or multiple name servers to fetch results from typically your ISP dns server(s) or you can use 8.8.8.8 by Google eg.
forwarders {
8.8.8.8; };
Zone : it gives meaning to call top domains like eg. menulab.com a namespace. Information about such a namespace (top domain) is stored in zones. On Ubuntu the zones are listed in /etc/bind/named.conf.local and each zone listing have a reference to a zone file, which then contains the namespace information (the zone file listing within named.conf.local may contain some additional management information, eg. if the zone can be transferred to another registrar or another person)
Zone file characters :
$ : signifies the beginning of a directive, eg.
$TTL : start of zone file and sets the default Time-To-Live (in seconds) for all resource records, specifying the time that a zone resource record is valid (should be cached by caching nameservers, eg. in your router)
$INCLUDE :
$ORIGIN : eg. $ORIGIN menulab.com. : means that any named used in a resource record NOT ending in a dot '.' are appended with menulab.com. Note that if $ORIGIN is not specified, then often the zone name is used by default - therefore often it is not necessary to specify the $ORIGIN directive.
@ : namespace variable either $ORIGIN or zone name (if $ORIGIN is not specified). @ is commonly used to avoid writing the zone namespace in resource records.
. : dot '.' is used to end a name signifying that it should NOT be appended $ORIGIN (or zone name).
( ) : groups data that crosses a line boundary (line terminations are not recognized within parentheses, however comments ending are)
; : start of comment (end of line will stop the comment).
\ : used to escape charaters with special meaning, eg. \. would translate to an actual dot.
Zone file format :
$ORIGIN : optional start of zone file specifying the namespace.
$TTL : start of dns node tree and the starting point of the dns zone file if no $ORIGIN is specified and default expiration time of all resource records in case they don't specify their own TTL's.
Resource Records : (a zone file can have multiple records of different types, see record types under format below)
Format :
host label : hostname of a record.
ttl : Time To Live : how long time other nameservers should cache this record
record class :
IN : INternet : default
CH : CHaosnet) : used for querying dns server versions.
HS : HeSiod : uses dns functionality to provide access to database of information that change infrequently.
record type :
SOA : Start of Authority : required option for each zone. SOA contains
name of the zone.
primary nameserver containing the original zone file (typically also specified as one of the authoritative nameservers using the NS record type).
email address on the entity responsible for administering the zone file (registrars show this as the administrator email for a domain). Note that the email address uses a dot '.' instead of add '@'.
serial number specifying date and increases by 1 for each update to the zone file.
minimum-ttl : negative response caching time by the nameserver.
For zones on which this nameserver is a secondary nameserver :
time-to-refresh : how long time (in seconds) the nameserver should wait before checking for an update in the primary zone file (comparing serial numbers).
time-to-retry : how long time to wait before retrying if cannot check the primary zone.
time-to-expire : how long time before the nameserver considers it's copy of the zone file to be expired and must stop answering requests (if it cannot update it's copy from the primary nameserver).
A : IPv4 Address : returns an IPv4 IP address, most commonly used to map hostnames to an IP address.
AAAA : IPv6 Address : returns an IPv6 address, same function as IPv4 but with 128 bit address space instead of 32 bit.
CNAME : Canonical NAME : also called an alias. In the example below www expands to www.menulab.com. (per $ORIGIN) and CNAME specifies that the canonical name for www.menulab.com. is menulab.com. Therefore if there are a forward lookup request for www.menulab.com return the result for menulab.com instead. $ORIGIN menulab.com. menulab.com IN A 27.254.33.97 www IN CNAME menulab.com.
MX : Mail eXchange : maps a domain name to a list of message transfer agents for that domain.
NS : Name Server : specifies the authoritative nameserver (there can be more than one authoritative nameserver). Below dns.webmodelling.com is tha authoritative nameserver for menulab.com : menulab.com. IN NS dns.webmodelling.com.
PTR : PoinTeR : used for reverse lookup (IP to domain)
SRV :
TXT : Text : orignally for arbitrary human-readable text in a dns record. Now this record more often carries machine-readable data, eg. SPF, DKIM, DMARC, DNS-SD etc.
Example : Note how dns.webmodelling.com & dns2.webmodelling.com both are authoritative (specified using NS records), but only dns.webmodelling.com is primary (specified in SOA record)
$TTL 3600
@ IN SOA dns.webmodelling.com. rasmus.topiqs.online. (
cmd> nslookup menulab.com dns.webmodelling.com : forward lookup (of menulab.com) requesting a specific nameserver (dns.webmodelling.com).
server : p396-static.nasbkkst2.c.csloxinfo.net : reverse lookup of nameserver (here different from dns.webmodelling.com)
Address : 202.183.164.142 : IP address of nameserver used (that is : IP of dns.webmodelling.com)
Name : menulab.com : the domain we make a forward lookup for.
Address : 27.254.33.57 : the IP of menulab.com
cmd> nslookup topiqs.online :
cmd> nslookup -type=soa topiqs.online :
cmd> nslookup -type=ns topiqs.online :
cmd> nslookup -type=mx topiqs.online :
cmd> nslookup -type=any topiqs.online : get all dns records for a domain.
cmd> nslookup 5.231.220.25 : reverse lookup.
cmd> nslookup -debug topiqs.online : detailed information for both dns request & response.
shell> dig topiqs.online any : get all dns resource records for a domain, however the nameserver may not supply dns records for any sub-domains.
KVM/QEMU
shell> egrep -c '(vmx|svm)' /proc/cpuinfo : whether the host CPU supports virtualization (cpu vendor : vmx=intel, svm=amd)
0 : no support
1 or more : support
shell> kvm-ok : shows whether KVM acceleration can be used
shell> lsmod | grep kvm : shows whether the kvm module have been loaded (and whether it is intel or amd).
If the kvm module have not been loaded, it can possible be loaded using the modprobe command : shell> modprobe kvm_intel : (in case of intel cpu)
shell> virt-viewer vmName : pass local screen for VM to remote client (the remote windows client should have Xming installed and the SSH connection should forward window X)
shell> osinfo-query os | grep Ubuntu : list all supported ubuntu variants for kvm.
Virsh
shell> virsh list --all : shows all virtual machines, their IDs and whether they are running
shell> virsh start vmName : startup this VM
shell> virsh shutdown vmName : stop this VM
shell> virsh destroy vmName : stop this VM
shell> virsh reboot vmName : reboots this VM
shell> virsh autostart vmName : set this VM to startup automatically on host boot.
shell> virsh autostart --disable vmName : set this VM to NOT startup automatically.
shell> virsh dumpxml vmName : write xml definition file for this VM to screen
shell> virsh define /path/to/VM/xml/file : creates a new VM domain and writes an xml definition file vmName (as specified in the source xml file) in /etc/libvirt/qemu
shell> virsh undefine vmName : deletes the xml definition file in /etc/libvirt/qemu for this VM and also removes the VM domain
shell> virsh net-list --all : show all virtual networks
shell> virsh net-info virtualNetworkName : shows info about a particular virtual network
shell> virsh console vmName : connect to the virtual machines console (since the console command will load virt-viewer, you need to run this from a remote ssh connection with graphics, eg. from Putty,Xming or from an Ubuntu desktop terminal).
shell> virsh net-dumpxml virtualNetworkName : write the network definition
shell> virsh dominfo vmName : some info about the guest.
shell> virsh vcpuinfo vmName : info about the virtual CPU of the guest.
shell> virsh nodeinfo : some info about the host.
shell> virsh edit vmName : loads /etc/libvirt/qemu/vmName.xml file in Vim - I use this only then I have copied the VM xml file, this typically means you have to edit the hardware address of the virtual network card as well as the source file of the virtual hard drive.
Popup's are required for topiqs.online core functionality - opening a collection of urls in tabs. Here is how to allow popup's for topiqs.online in various browsers.
In Chrome you can allow popups for topiqs.online from the right corner of the url-field :
In FireFox you will get a very easy to spot yellow dialog with an options button you can click to allow popups for topiqs.online.
In Edge the option to allow popups for topiqs.online is located at the bottom of the browser window. (Note that the Edge version of writing does NOT allow you to revoke popup permissions once granted).
In Internet Explorer 11 the option to allow popups for topiqs.online is located at the bottom of the browser window.
Urls
nslookup menulab.com dns.webmodelling.com : forward lookup (of menulab.com) requesting a specific nameserver (dns.webmodelling.com).
