To understand how VLANs work, let’s consider VLAN applications in a traditional IT environment, where physical hosts are attached to a physical switch, and no virtualization is involved. Imagine a scenario where you want three isolated networks but you only have a single physical switch. The network administrator would choose three VLAN IDs, for example,… Continue reading How Vlan works in plain language
Category: Sysadmin
Docker under the hood
Many people think that docker is a kind of monolithic system and they hardly understand how internally it works. see the figure below
checking who is connecting with nfs server
cat /var/lib/nfs/rmtab
Fixed sysctl: cannot stat /proc/sys/net/bridge/bridge-nf-call-iptables:
sysctl: cannot stat /proc/sys/net/bridge/bridge-nf-call-iptables: No such file or directory sysctl: cannot stat /proc/sys/net/bridge/bridge-nf-call-ip6tables: No such file or directory solution: modprobe br_netfilter
slashargument no image css appear issue in moodle 2.9+ nginx FIXED
location ~ [^/]\.php(/|$) { fastcgi_split_path_info ^(.+\.php)(/.+)$; fastcgi_index index.php; fastcgi_pass 127.0.0.1:9000 (or your php-fpm socket); include fastcgi_params; fastcgi_param PATH_INFO $fastcgi_path_info; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; }
ipmitool dev not found
modprobe ipmi_devintf modprobe ipmi_si You can add these to /etc/modules to have them loaded automatically (just list the module names): ipmi_devintf ipmi_si
linux gateway
iptables -A FORWARD -i eth1 -j ACCEPT iptables -A FORWARD -o eth1 -j ACCEPT iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE #ETHO where internet is connected
Get MD5 checksum hash of big files in Python
def checkHash(filename, blocksize=2**20): try: print(“need to creating hash of file ” +filename) m = hashlib.md5() with open(filename , “rb” ) as f: while True: buf = f.read(blocksize)… Continue reading Get MD5 checksum hash of big files in Python
cinder volume service down fixed
it is mostly date issue check date on both controller and cinder-volume server and do ntpdate 1.ubuntu.pool.ntp.org
No space left on device: AH00023: Couldn’t create the rewrite-map mutex
To clear all semaphores owned by the apache user: Raw ipcs -s | awk -v user=apache ‘$3==user {system(“ipcrm -s “$2)}’