Let’s store more tips I’ve been collecting during last times.
Export http proxy linux shell
export http_proxy=http://10.0.0.1:61010
export https_proxy=http://10.0.0.1:61010
Apt-Cache madison
It displays available versions of a package in a tabular format.
Try with
apt-cache madison myPackage
Use of Grep
Try the following:
grep -v -e '^$' foo.txt
The -e option allows regex patterns for matching.
The single quotes around ^$ makes it work for Cshell. Other shells will be happy with either single or double quotes.
UPDATE: This works for me for a file with blank lines or “all white space” (such as windows lines with “\r\n” style line endings), whereas the above only removes files with blank lines and unix style line endings:
grep -e -v '^[[:space:]]*$' foo.txt
Exlcude # and empty lines
egrep -v "^#|^$" foo.txt
Git tips
bash completion
There are other ways to enable git-bash-completion depending on your OS.
For linux you can just do the following:
First get the git-completion.bash script (view it here) and put it in your home directory:
curl https://raw.githubusercontent.com/git/git/master/contrib/completion/git-completion.bash -o ~/.git-completion.bash
Next, add the following lines to your .bash_profile. This tells bash to execute the git autocomplete script if it exists.
if [ -f ~/.git-completion.bash ]; then
. ~/.git-completion.bash
fi
End with
source ~/.bash_profile
add file from one branch to other
git checkout master # first get back to master
git checkout experiment -- app.js # then copy the version of app.js
# from branch "experiment" ---
Use of SED
If you want to delete lines 5 through 10 and 12:
sed -e '5,10d;12d' file
This will print the results to the screen. If you want to save the results to the same file:
sed -i.bak -e '5,10d;12d' file
This will back the file up to file.bak, and delete the given lines.
To delete line 5, do:
sed -i -e '5d' file.txt
For a variable line number:
sed -i -e "${line}d" file.txt
If the -i option isn’t available in your flavor of sed, you can emulate it with a temp file:
sed "${line}d" file.txt > file.tmp && mv file.tmp file.txt
PV shows progress on dd, tar and others
Decompressing with TAR
tar -czf - ./Downloads/ | (pv -p --timer --rate --bytes > backup.tgz)
Using DD to write image on disk
pv -tpreb debian-live-8.5.0-amd64-standard.iso | sudo dd of=/dev/disk1 bs=1m
dd if=/dev/urandom | pv | dd of=/dev/null
mdadm raid
First examine your drives to see their uuids with
mdadm --examine --scan
Enable or assemble the raid volume
mdadm --assemble --uuid <uuid> /dev/md0
Mount your drive
mount /dev/md0 /my/destination/folder
Iptables
Blocking access to a certaing port
iptables -A OUTPUT -p tcp -d 192.168.1.2 --dport 5050 -j DROP
How to forward correctly a port, I finally found how-to. First, I had to add -i eth1 to my “outside” rule (eth1 is my WAN connection). I also needed to add two others rules. Here in the end what I came with :
iptables -t nat -A PREROUTING -i eth1 -p tcp --dport 8080 -j DNAT --to 10.32.25.2:80
iptables -t nat -A PREROUTING -p tcp --dport 8080 -j DNAT --to 10.32.25.2:80
iptables -t nat -A POSTROUTING -p tcp -d 10.32.25.2 --dport 80 -j MASQUERADE
Echo just for fun
echo "I'm a Unix Creationist, the world was created on $(TZ=GMT date -d @0) and it will end on $(TZ=GMT date -d @$((2**31-1)))"
CENTOS tips
change timezone centos
# cp /usr/share/zoneinfo/GB /etc/localtime
ifconfig
yum install net-tools
static network address
vi /etc/sysconfig/network-scripts/ifcfg-eth0
I will change the file like this:
#My IP description
# IPv-4
DEVICE="eth0"
NM_CONTROLLED="yes"
ONBOOT=yes
HWADDR=20:89:84:c8:12:8a
TYPE=Ethernet
BOOTPROTO=static
NAME="System eth0"
UUID=5fb06bd0-0bb0-7ffb-45f1-d6edd65f3e03
find files from packages
yum whatprovides ifconfig
Send data through netcat
On your server (A):
nc -l -p 1234 -q 1 > something.zip < /dev/null
On your “sender client” (B):
cat something.zip | netcat server.ip.here 1234
Smbcredentials
Using a text editor, create a file for your remote servers logon credential:
gedit ~/.smbcredentials
Enter your Windows username and password in the file:
username=msusername
password=mspassword
Save the file, exit the editor.
Change the permissions of the file to prevent unwanted access to your credentials:
chmod 600 ~/.smbcredentials
Mount with the following options in /etc/fstab
//your_server/Your_Share /mnt/samba/Your_Mount cifs credentials=/home/your_home_directory/.smbcredentials,uid=yourlinuxaccount,gid=users 0 0
Or through command line with
mount -t cifs //your_server/Your_Share -o credentials=/home/your_home_directory/.smbcredentials
disable ipv6
To disable ipv6, you have to open /etc/sysctl.conf using any text editor and insert the following lines at the end:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
If ipv6 is still not disabled, then the problem is that sysctl.conf is still not activated.
To solve this, open a terminal(Ctrl+Alt+T) and type the command,
sudo sysctl -p
You will see this in the terminal:
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
After that, if you run:
$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6
It will report:
1
If you see 1, ipv6 has been successfully disabled.
Vlan debian
$ sudo apt-get install vlan
$ sudo modprobe 8021q
vconfig manages vlan
# vconfig rem eth1.10
Removed VLAN -:eth1.10:-
# ip a l eth1.10
Device "eth1.10" does not exist.
Forward to a Gmail mail server
To configure SSMTP, you will have to edit its configuration file (/etc/ssmtp/ssmtp.conf) and enter your account settings:
#/etc/ssmtp/ssmtp.conf
# The user that gets all the mails (UID < 1000, usually the admin)
[email protected]
# The mail server (where the mail is sent to), both port 465 or 587 should be acceptable
# See also https://support.google.com/mail/answer/78799
mailhub=smtp.gmail.com:587
# The address where the mail appears to come from for user authentication.
rewriteDomain=gmail.com
# The full hostname
hostname=localhost
# Use SSL/TLS before starting negotiation
UseTLS=Yes
UseSTARTTLS=Yes
# Username/Password
AuthUser=username
AuthPass=password
# Email 'From header's can override the default domain?
FromLineOverride=yes
Note: Take note, that the shown configuration is an example for Gmail, You may have to use other settings. If it is not working as expected read the man page man 8 ssmtp, please.
Create aliases for local usernames (optional)
/etc/ssmtp/revaliases
root:[email protected]:smtp.gmail.com:587
mainuser:[email protected]:smtp.gmail.com:587
Install basic mail application
apt-get install bsd-mailx
To test whether the Gmail server will properly forward your email:
$ echo test | mail -v -s "testing ssmtp setup" [email protected]
nmap snmp
You can use Nmap’s snmp-brute something like
nmap -sU -p161 --script snmp-brute --script-args snmplist=community.lst 192.168.1.0/24
check_mk
root@linux# cmk -II df xyzsrv01
This first removes all checks of type df on host xyzsrv01 and then does inventory.
Example 2:
root@linux# cmk -II xyzsrv01
This removes all agent based of host xyzsrv01 before doing inventory.
ras-pi best practices
raspi-config
- expand filesystem
- change timezone, keyboard, hostname
First make sure (if you haven’t already) that your raspian is up to date. type:
sudo apt-get update
sudo apt-get upgrade
It is also a good idea to make sure your firmware is up to date
sudo apt-get install rpi-update
and run it
sudo rpi-update
a reboot is required when this is finished
sudo shutdown -r now
(you will have to reconnect via ssh when the Rpi has restarted if you are using a remote terminal)
rpi-cam
To enable video0 on raspi
sudo modprobe bcm2835-v4l2
update-rc.d debian
Managing a service
Default priorities
If you want to re-add this service to be started on boot up, you can simply use:
update-rc.d apache2 defaults
Specifying custom runlevels
If you only want to Start and Kill on specific runlevels, like for instance starting apache with priority 20 on runlevels 2, 3, 4 and 5 and Kill with priority 80 on runlevels 0, 1 and 6:
update-rc.d apache2 start 20 2 3 4 5 . stop 80 0 1 6 .
HOWTO: Repair filesystem using fsck on a raid setup
-
Step 1.
$ mdadm --examine --scan >> /etc/mdadm.conf -
Step 2.
$ mdadm --assemble /dev/md2 mdadm: /dev/md2 has been started with N drives. -
Step 3.
From here it works like any normal fsck.
$ fsck /dev/md2
MySQL basics
Create BBDD
[root@server html]# mysqladmin –u yourmysqladminuser –p create yourdatabase
Enter password:
Import BBDD from sql file
[root@server html]# mysql -u root -p yourdatabase<backup_databse.sql
give user permissions
[root@server html]# mysql –u yourmysqladmin –p Enter password:
mysql> grant all on database.* to dbuser@localhost identified by 'password';
full access from anywhere
GRANT ALL PRIVILEGES ON *.* TO 'dbuser'@'%';
Give password to user
mysql> UPDATE user SET Password=PASSWORD('newpass') WHERE User='root';
mysql> flush privileges ;
mysql>exit
Dump database
mysqldump -u root -pPASSWORD basededatos > basededatos.dump.sql
Ulimits
Check Hard Limit in Linux
# ulimit -Hn
4096
Check Soft Limits in Linux
# ulimit -Sn
1024
Set new limits
# vi /etc/security/limits.conf
Add the following to limits.conf
http hard nofile 4096
http soft nofile 1024
ZFS commands to check your pool
zpool status -v
zpool list -v
zpool get ashift
zfs list -space,compressratio,recordsize,volblocksize -r -t all