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In addition to the other storage devices on my laptop, running df -h displays /cow as one of the devices. What does this mean?

Jeff
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Beldar
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1 Answers1

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I think you are running a live (live-only or persistent live Ubuntu system). Such systems run with the root file system in RAM and the device is called cow (which refers to 'copy on write').

A live-only system allocates typically half of the available RAM for the root file system. A persistent live system uses an overlay system, where the partition (or file) for persistence is overlayed on the RAM for the root file system.

Example 1: A live-only system in a computer with 16 GiB RAM

lubuntu@lubuntu:~$ df -h
Filesystem                   Size  Used Avail Use% Mounted on
tmpfs                        1.6G  9.8M  1.6G   1% /run
/dev/sdb1                    1.8G  1.8G     0 100% /cdrom
/cow                         7.8G   17M  7.8G   1% /
/dev/disk/by-label/writable   54G   55M   51G   1% /var/log
tmpfs                        7.8G     0  7.8G   0% /dev/shm
tmpfs                        5.0M  4.0K  5.0M   1% /run/lock
tmpfs                        4.0M     0  4.0M   0% /sys/fs/cgroup
tmpfs                        7.8G     0  7.8G   0% /tmp
tmpfs                        1.6G   80K  1.6G   1% /run/user/999

Example 2: A persistent live system in an SSD with 60 GB connected via USB

lubuntu@lubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           1.6G  1.8M  1.6G   1% /run
/dev/sda1       1.8G  1.8G     0 100% /cdrom
/cow             54G   81M   51G   1% /
tmpfs           7.8G     0  7.8G   0% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           4.0M     0  4.0M   0% /sys/fs/cgroup
tmpfs           7.8G     0  7.8G   0% /tmp
tmpfs           1.6G   80K  1.6G   1% /run/user/999
/dev/sda4        54G   81M   51G   1% /media/lubuntu/writable

You can create both kinds of systems with mkusb

sudodus
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